question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Im currently testing the reliability and validity of the SERVQUAL model (measuring just the items for each dimension. Hence these items should load on just factor). My supervisor wants me to include individual item reliability. She said this will be found in the factor analysis. The question is: is found in the comm... | g63833 | [
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<p>I'm reading "The theory that would not die" by Sharon Bertsch McGrayne (Fine book. Strongly recommended to everyone). The author says that bayesian inference has been used for ballistics applications at least three times in the last three centuries:</p>
<p>1) By Joseph Louis François Bertrand (<a href="http://en.wi... | g63834 | [
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<p>The <a href="http://en.wikipedia.org/wiki/Scatter_matrix" rel="nofollow">scatter matrix</a> is defined as </p>
<p>$$S = \sum_{j=1}^n (\mathbf{x}_j-\overline{\mathbf{x}})(\mathbf{x}_j-\overline{\mathbf{x}})^T$$</p>
<p>The trace (sum of the diagonal elements) of this matrix is equivalent to the overall sum of square... | g49685 | [
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<p>I've got SNA data for three groups of chimpanzees and I'm looking to do some basic analysis across and between groups. Does anyone by any chance know how to compare social network data between groups (for example, scores of strength from enclosure 1 vs enclosure 2), and/or 2) combine data from different groups (for ... | g63835 | [
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<p>Why is it necessary to place the distributional assumption on the errors, i.e.</p>
<p>$y_i = X\beta + \epsilon_{i}$, with $\epsilon_{i} \sim \mathcal{N}(0,\sigma^{2})$.</p>
<p>Why not write</p>
<p>$y_i = X\beta + \epsilon_{i}$, with $y_i \sim \mathcal{N}(X\hat{\beta},\sigma^{2})$,</p>
<p>where in either case $\e... | g63836 | [
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<p>Let $\phi_1,\ldots,\phi_n$ denote characteristic functions for distributions on the real line. Let $a_1,\ldots,a_n$ denote nonnegative constants such that $a_1+\ldots+a_n = 1$. Show that</p>
<p>$$\hspace{20mm} \phi(t) = \sum_{j=1}^{n}a_j\phi_j(t), \hspace{8mm}-\infty<t<\infty$$</p>
<p><strong>Attempt:</stron... | g63837 | [
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<p>I previously asked this <a href="http://stats.stackexchange.com/q/2917/1381">question</a> about the validity of my solutions for for $SE$ given $n$, $\bar{X_i}$ and summary statistics from post-hoc multiple comparisons such as Fisher's $LSD$ and Tukey's $HSD$, but I would like a general approach that can be applied ... | g63838 | [
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<p>I have a database containing a large number of experts in a field. For each of those experts i have a variety of attributes/data points like:</p>
<ul>
<li>number of years of experience.</li>
<li>licenses</li>
<li>num of reviews</li>
<li>textual content of those reviews</li>
<li>The 5 star rating on each of those re... | g63839 | [
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<p>Lets assume you are a social science researcher/econometrician trying to find relevant predictors of demand for a service. You have 2 outcome/dependent variables describing the demand (using the service yes/no, and the number of occasions). You have 10 predictor/independent variables that could theoretically explain... | g63840 | [
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<p>Asked to compute estimator for the following function,</p>
<p>$\theta = \int_0^\infty e^{-x^2}$</p>
<p>which can be solved by transforming the limits to 0 to 1 and solving the following expectation using Monte Carlo,</p>
<p>$$ E[1/U \space e^{-1(-1+1/U)^2}]$$</p>
<p>where $U$ is uniformly distributed</p>
<p>The... | g63841 | [
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<p>I hear it said <strong><em>[1]</em></strong> that QR makes no distribution assumptions about its error term. </p>
<p><strong>Question 1</strong>: Does this mean that heteroscedastic and serially correlated disturbances do not effect the unbiasedness, consistency and minimum variance property of the coefficient esti... | g63842 | [
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<p>I've been looking over some regression models lately and I came across one which, although similar, differs from the "standard" simple linear model. I was hoping somebody could provide some assistance with some properties that I'm confused with.</p>
<p>Assuming the regression form:</p>
<p>$y_{i} = \beta_{0} + \bet... | g21711 | [
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<p>For those of us that work in data mining building predictive models what is the benefit of a Bayesian belief net? I am sure I am just naive as I have not studied them in depth, but what are the advantages? </p>
<p>It seems to me that on the surface, from a prediction stand point, there are typically better classifi... | g42361 | [
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<p>I created a synthetic constant image (all the pixel values are the same) on which I generated a Poisson distribution using a Poisson noise generator, with mean values set to input pixel values. </p>
<p>Then, I applied the Anscombe transform and checked if the output distribution fit the normal distribution by using... | g63843 | [
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<p>I am looking for a way to find an optimal value among several combinations of values.</p>
<p>The data looks like this:</p>
<pre><code> N V MDO MLO ERROR
1231 50.0 4.0 0.010 0.143
131 10.0 8.0 0.002 0.150
1319 40.0 4.5 0.050 0.150
13410 20.0 9.0 0.025 0.146
5231 50.0 3.5 0... | g63844 | [
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<p>I am trying to get a global perspective on some of the essential ideas in machine learning, and I was wondering if there is a comprehensive treatment of the different notions of loss (squared, log, hinge, proxy, etc.). I was thinking something along the lines of a more comprehensive, formal presentation of John Lan... | g63845 | [
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<p>Is there a white noise which is not ergodic?</p>
<p>How is the ergodicty of a white noise tested?</p>
<p>Thanks!</p>
<p>Note: A white noise is defined as in <a href="http://books.google.com/books?id=_DcYu_EhVzUC&lpg=PP1&dq=white%20noise%20%20brockwell%20time%20series&pg=PA78#v=onepage&q&f=fals... | g63846 | [
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<p>ANOVA is equivalent to linear regression with the use of suitable dummy variables. The conclusions remain the same irrespective of whether you use ANOVA or linear regression. </p>
<p>In light of their equivalence, is there any reason why ANOVA is used instead of linear regression? </p>
<p>Note: I am particularly i... | g63847 | [
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<p>Is there a decomposition for mean absolute deviation which is comparable to that for MSE, e.g., <a href="http://en.wikipedia.org/wiki/Brier_score#Decompositions" rel="nofollow">Brier score decomposition</a>?</p>
<p>The setting here is the same: a binary classification problem, and a decomposition which has somethin... | g63848 | [
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<p>Let us say that we have this following problem:</p>
<p>"A government agency claims that more than 50% of US tax returns were filed electronically last year. A random sample of 150 tax returns for last year contained 86 that were filed electronically. Test the claim at $\alpha = 0.05$ significance level."</p>
<p>In... | g15230 | [
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<p>I have a dataset:</p>
<ul>
<li>Response: categorical, 9 levels.</li>
<li>23 predictors: binary, with many 0's.</li>
<li>Number of samples: 64.</li>
</ul>
<p>I'm interested to know the dependence of (each level of) the response on predictors. </p>
<p>Grateful for any suggestion to start.</p>
<p><strong>Edit</stro... | g63849 | [
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<p>I have collected data from employees at 13 branches of a bank and also administered customer satisfaction scale to customers of each of the branches. As a result, I am unable to have pairs of observations for each case of data at the individual level. To deal with this, I have contemplated aggregating by computing t... | g63850 | [
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<p>I have calculated a posterior</p>
<p>$p(P_1, P_2 | D)$</p>
<p>where $P_1$ has a few and $P_2$ has many dimensions. In the process of calculating the <a href="http://en.wikipedia.org/wiki/Maximum_a_posteriori" rel="nofollow">maximum a posteriori estimate</a> for $(P_1,P_2)$ given certain data $D$, I calculate the m... | g63851 | [
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<p>This is more of a historical related question. Edmond Halley in 1693 published an <a href="http://www.pierre-marteau.com/editions/1693-mortality.html" rel="nofollow">actuarial table</a> showing mortality rates. The tables show yearly statistics for ages 1-84 and a summary statistic for ages 84-100. I have searched h... | g63852 | [
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<p>Say $k \sim Bin(N, p)$. What is the distribution of $N$, given fixed $p$ and $k$? Looks like Poisson but starting at k instead of zero (???) </p>
<p>Thanks.</p>
<p><strong>EDIT:</strong> Application: I have some real number of birds ($N$), each is seen with probability $p$. I see $k$ birds and want to estimate the... | g63853 | [
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<p>Let $X_1,X_2,\cdots ,X_j \cdots $ be i.i.d. $\mathcal N(0, 1)$ random variables. Show that
for any $a > 0$, $$\lim_{n\to \infty}P\left( \sum_{i=1}^n X_i^2\leq a\right)=0$$
It is clear that $\sum_{i=1}^n X_i^2 \sim \chi ^2_n$; then, I can't proceed. Please help.</p> | g44589 | [
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<p>I'm using the ANES dataset, which is a repeated cross-sectional study of public opinion and knowledge. I am trying to predict knowledge by individual level characteristics. The data is organized by year, and each respondent is grouped by age into an age cohort. </p>
<p>Essentially, I am trying to run multiple mu... | g63854 | [
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<p>I need the best machine learning method/algorithm/technique to predict energy consumption. The given training dataset consists of 2 years of energy consumption, with entries every 15 minutes. In addition, weather data (radiation, humidity, temperature and wind speed) are given every hour.</p>
<p>Now as input, I hav... | g34 | [
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<p>I am trying to implement the <a href="http://www.scholarpedia.org/article/Grassberger-Procaccia_algorithm" rel="nofollow">Grassberger Procaccia algorithm</a>. I have got stuck in how to find the summation of the correlation integral. The following code computes the correlation dimension in the polyfit command. I ca... | g63855 | [
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<p>I'm curious to know what others tend to see as a suitable naming convention for model features or variables, particularly as they relate to their use and reference in software applications.</p>
<p>For instance, given two inputs: <strong>age</strong> and <strong>income</strong>, we could construct features around va... | g63856 | [
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-0.008972116746008396,
0.008447566069662571,
-0.04138761758804321,
0.0978090837597847,
... |
<p>Stepwise Regression works as follows if I'm correct:</p>
<ol>
<li>fit the initial model</li>
<li>add the variable which has its f-stat larger than a in-threshold and repeat step 2. if there are no candidates to enter - go to step 3</li>
<li>if there is a variable with f-stat less than a out-threshold, remove this v... | g21723 | [
0.005432897247374058,
-0.0218285471200943,
-0.010877138003706932,
-0.0397329181432724,
-0.01402386836707592,
-0.020482216030359268,
0.01671854592859745,
0.07482458651065826,
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-0.01148969866335392,
-0.035226717591285706,
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0.01... |
<p>I'm trying to understand the Newman Modularity (doi:10.1073/pnas.0601602103) by investigating its calculation on the <a href="https://en.wikipedia.org/wiki/Modularity_%28networks%29" rel="nofollow">Wikipedia example </a>
. My question is why are probabilities of self-loops included in the Q formula while the adjacen... | g63857 | [
0.0029856227338314056,
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-0.017497273162007332,
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0.031254615634679794,
0.002344494452700019,
... |
<p>Let's say, we have some random event. We also have a hist of time intervals between two events, based on statistical data. For example, a frequency distribution: </p>
<pre><code>[100,30,15,10,7,6,5,5,4,4]
</code></pre>
<p>Each bin value corresponds to length of time interval between two events. 1st bin corresponds... | g42365 | [
0.07874149084091187,
0.023437881842255592,
-0.019454726949334145,
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0.03298510983586311,
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0.049606844782829285,
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0.02261780947446823,
0.026309696957468987,
-0... |
<p>I have read the help manual of caret carefully: see A Short Introduction to the caret Package.</p>
<p>In its example, I found it split the data with createDataPartition before a model training.</p>
<pre><code>library(caret)
library(mlbench)
data(Sonar)
set.seed(107)
inTrain <- creatDataPartition(y = Sonar$Class... | g21725 | [
-0.007195536512881517,
-0.045350685715675354,
-0.001342692761681974,
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0.055657267570495605,
0.0022193333134055138,
0.08951020240783691,
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-0.04527607932686806,
-0.03689848631620407,
0.019169708713889122,
0.0532137006521225,
... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/421/what-book-would-you-recommend-for-non-statistician-scientists">What book would you recommend for non-statistician scientists?</a> </p>
</blockquote>
<p>Could anyone suggest a concise book/tutorial on s... | g49417 | [
0.055979207158088684,
0.007518838159739971,
0.028103850781917572,
0.009448489174246788,
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0.0054603745229542255,
-0.02875293418765068,
0.02745749056339264,
0.008433680981397629,
0.02289857342839241,
0.027429884299635887,
0.0202805083245039,
-0.0124... |
<p>First, a little background:</p>
<p>I'm a college paintball coach and I'm trying to identify which of my players have the biggest impact on various statistics (e.g. winning percentage etc). </p>
<p>In order to do this I've put together a csv file with the following columns for each point that we play (you can use h... | g63858 | [
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0.028391936793923378,
0.00... |
<p>Suppose I have $n$ data sets where each variable has the same variable types, but possibly a different number of data points. For instance, age, sex, and height, for $n$ different counties. After performing analysis (linear, logistic, Poisson, etc..) on each data set (country), how do I display information for all... | g21726 | [
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0.0004400559118948877,
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0.0023362969513982534,
0.07454319298267365,
... |
<p>I'm currently experimenting with Gaussian processes.
I decided to use matlab + gpml (<a href="http://www.gaussianprocess.org/gpml/code/" rel="nofollow">http://www.gaussianprocess.org/gpml/code/</a>) for playing around with Gaussian processes a bit.</p>
<p>I'd like to do Gaussian process regression on 2d data. For ... | g48753 | [
0.010669289156794548,
-0.011713107116520405,
0.000997265917249024,
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0.020578918978571892,
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-0.06176358088850975,
0.0012002490693703294,
0.04899471253156662,
0.03036174736917019,
-0.01... |
<p>I would like to generate a set of artificial data using another input set from which correlations between variables can be extracted. Not all variables are binary, but the data can easily be extended to be so, at the cost of increased dimensionality.</p>
<p>I was only able to find a method for the generation of cor... | g44842 | [
0.028778860345482826,
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0.02965841442346573,
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0.01184216607362032,
0.03... |
<p>In the context of online clustering, I often find many papers talking about: "dirichlet process" and "finite/infinite mixture models".</p>
<p>Given that I've never used or read about dirichlet process or mixture models. Do you know any suggestions of introductory lectures or papers that are easy to understand, abou... | g21727 | [
-0.006304549518972635,
0.000951112131588161,
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... |
<p>I'm checking a timeserie with:</p>
<ul>
<li><strong>ADF</strong> (unitroot)</li>
<li><strong>KPSS</strong> (unitroot)</li>
<li><strong>Phillips-Ouliaris</strong> (cointegration)</li>
</ul>
<p>the results are:</p>
<p><strong>Phillips-Ouliaris</strong></p>
<pre><code>Phillips-Ouliaris demeaned = -2175.5676, Trunca... | g63859 | [
-0.0021285268012434244,
-0.02275325544178486,
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0.03153099864721298,
0.027331484481692314,
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0.03135322406888008,
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0.05392695218324661,
0.04942144453525543,
-0.080... |
<p>I am learning R and have been experimenting with analysis of variance. I have been running both</p>
<pre><code>kruskal.test(depVar ~ indepVar, data=df)
</code></pre>
<p>and </p>
<pre><code>anova(lm(depVar ~ indepVar, data=dF))
</code></pre>
<p>Is there a practical difference between these two tests? My underst... | g63860 | [
0.01994413509964943,
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0.008942821063101292,
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0.01887138932943344,
0.021619729697704315,
0.03241361677646637,
0.0... |
<p>Background: Eight doctors each rated the same 54 patients on a persuasiveness measure (1-7 Likert scale). The mean score on the persuasiveness measure will eventually be the outcome measure of my experiment. </p>
<p>Inter-rater reliability was quantified as the intraclass correlation coefficient (ICC), using the tw... | g63861 | [
-0.020813975483179092,
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0.0008517981041222811,
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0.031466275453567505,
0.032478924840688705,
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... |
<p>Is it possible to express the kurtosis $\kappa$, or the 4th central moment $\mu_4$, of a random variable $X$ in terms of its mean $\mu = E(X)$ and variance $\sigma^2 = Var(X)$ only, without having to particularize to any distribution?</p>
<p>I mean, an expression like $\kappa = f(\mu, \sigma^2)$ or $\mu_4 = g(\mu, ... | g41152 | [
-0.033609893172979355,
0.011353788897395134,
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0.04164823517203331,
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0.025571376085281372,
-0.015530376695096493,
... |
<p>If in a linear regression I have categorical variable... how do I know the stastical signifance of the categorical variable?</p>
<p>Let's say the factor $X_1$ has 10 levels... there will be 10 different resultant t-values, under the umbrella of one factor variable $X_1$...</p>
<p>It seems to me that the statistica... | g49409 | [
-0.027122298255562782,
-0.027731232345104218,
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0.042491961270570755,
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0.022135118022561073,
0.031537238508462906,
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0.013654856942594051,
-0.06350286304950714,
0.02568482980132103,
0.0389820858836174,
0.... |
<p>I have a number of trading strategies, and trading systems which are subsets of
the strategies (many systems in one strategy).</p>
<p>I also have a number of market indicators created by a portfolio manager which
act like technical trading indicators which indicate his beliefs about certain
market conditions. </p>
... | g15332 | [
-0.01803826540708542,
0.029208248481154442,
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0.03862058371305466,
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0.01193862035870552,
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0.04603155702352524,
-0.029266687110066414,
0.034594908356666565,
0... |
<p><em>Working off a fairly limited statistical understanding, so apologies in advance if this question is ludicrously basic. This has to have happened to other people who have successfully solved this issue, but searching for what I think are relevant terms is getting me things like "Karlin's Conjecture for Random Re... | g63862 | [
-0.01235918141901493,
-0.010947616770863533,
0.0005227321526035666,
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0.00878076534718275,
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0.027822349220514297,
0.033886246383190155,
0.021020913496613503,
-0.027126211673021317,
0.04024273902177811,... |
<p>I have two independent continuous random variables, $A$ and $B$. I want to find the cumulative distribution function of $A+B$.</p>
<p>$A$ is log-logistically distributed, and $B$ is normally distributed.</p>
<p>How can I go about finding the CDF of $A+B$?</p> | g63863 | [
0.054317813366651535,
-0.030478615313768387,
-0.023788684979081154,
0.0032364819198846817,
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0.0035536442883312702,
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-0.052945610135793686,
-0.017465069890022278,
0.002338144928216934,
0.015528489835560322,
... |
<p>Is there a specific way of sampling which maintains the ratio of samples in an unbiased set? e.g., lets say I want to do k-fold cross-validation on my training set And my training set is very imbalanced (let's say 1:10) How can I sample such that each of the k-folds also has the same ratio of +/- (In this case, 1:10... | g63864 | [
-0.010249634273350239,
0.0038831213023513556,
0.02076488919556141,
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0.0027723258826881647,
0.007267567794770002,
0.048960186541080475,
-0.018344325944781303,
0.01817474141716957,
0... |
<p>I was reading Robert Serfling's 1980 book "Approximation Theorems of Mathematical Statistics" and came across the following construction of the Dvoretzky–Kiefer–Wolfowitz inequality for arbitrary distributions $F$, which DKW prove for distributions on $[0,1]$.</p>
<blockquote>
<p>Given independent $X_i$ with d.f... | g21739 | [
-0.023752819746732712,
0.0043404968455433846,
-0.02542167343199253,
-0.007188982330262661,
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0.016625825315713882,
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-0.024450121447443962,
-0.06456141918897629,
0.027942301705479622,
0.015508197247982025,
... |
<p>I have a dataset of 1000 tumours described by 6 parameters (my independent variables). For each tumour I have a value of the accuracy of 8 different segmentation methods.</p>
<p>I would like to build a model that can predict, given the 6 parameters describing a tumour, which segmentation method would yield the high... | g21741 | [
0.0009127106750383973,
-0.016547324135899544,
0.013425042852759361,
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0.030676985159516335,
-0.008883030153810978,
-0.006224986165761948,
0.012739022262394428,
-0.014809505082666874,
0.09094651788473129,
... |
<p>my level of stats is kind of restricted to some undergraduate courses.
Anyhow I received some data from a planned experiment. Basically it is about to test the shear strength (interval scale) for electronic devices. </p>
<p>The experiments should look for differences in different materials and process parameters.... | g63865 | [
-0.02067897468805313,
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0.009323827922344208,
0.08029495179653168,
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0.011688603088259697,
-0.017262453213334084,
0.010247847065329552,
0.05103706941008568,
0... |
<p>I am trying to use R to find the optimal solution for my problem with positive coefficients. Here are my data: </p>
<pre><code> th inp tcyc tinst tmem tcom
1 2 2 26219765385 1975872868 52449810 782964
2 2 4 38080459431 3155342008 76744867 1878903
3 2 8 64572439... | g63866 | [
-0.007749910932034254,
-0.03698002174496651,
-0.004294866696000099,
-0.024873849004507065,
0.00362178822979331,
-0.0904243215918541,
0.06966058909893036,
-0.0047292509116232395,
-0.0457611009478569,
0.008161620236933231,
-0.0749758929014206,
0.03765629604458809,
0.018282277509570122,
0.025... |
<p>Is it useful to include cross-level-interaction in multilevel (hierarchical) models without varying slopes (only varying intercept)?</p>
<p>A short example in R:</p>
<pre><code>m1 <- lme(y~x_1+x_2+z_1+z_2+x_1:z_1, random = ~1|county, data = data)
</code></pre>
<p>Where:</p>
<p>y = Response variable</p>
<p>x ... | g63867 | [
0.029173703864216805,
-0.02673945389688015,
-0.005496933124959469,
0.013897478580474854,
0.007609167136251926,
-0.0011739223264157772,
0.04876888170838356,
-0.0413389652967453,
-0.04811178892850876,
0.04436378926038742,
0.0023620519787073135,
0.016536733135581017,
0.008542526513338089,
0.0... |
<p>I'm trying to write an equation for a time series $\text{TS}$ containing noisy and unevenly sampled data from a function $m(t)$. Here's what I've come up with:</p>
<p>$$\text{TS}(t \in \mathcal{U}(0, 1)) = m(t) + \mathcal{N}(0, 0.1) \quad $$</p>
<p>or maybe</p>
<p>$$\text{TS}(t) = m(t) + \mathcal{N}(0, 0.1) \quad... | g21745 | [
-0.02420813776552677,
-0.04720206558704376,
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-0.0020432735327631235,
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-0.047902997583150864,
0.010912282392382622,
0.01224605180323124,
0.047201968729496,
0.015028893016278744,
-0... |
<p>I'm now preparing exams for mathematical statistics. Our teacher told us that there will be problems concerning the estimator for vectors(or matrices) that increases length when the number of samples increases. Here are some examples:</p>
<p>1 $X_1,\cdots,X_n$ are vectors of length $n$. The $k$th element of $X_i$, ... | g63868 | [
0.034108202904462814,
-0.014759650453925133,
0.00028064442449249327,
-0.016892926767468452,
-0.04131019487977028,
-0.06368357688188553,
-0.025629347190260887,
-0.021013310179114342,
-0.0275544635951519,
0.05156305804848671,
-0.01516678649932146,
0.047196246683597565,
0.01974712871015072,
0... |
<p>In my dataset, I have 2 labels, positive and negative. Most samples belong to only one class, either positive or negative. A small fraction of samples take both labels i.e. both positive and negative. Thus, making it a <a href="http://en.wikipedia.org/wiki/Multi-label_classification" rel="nofollow">multi-label</a> c... | g63869 | [
-0.035959698259830475,
0.0035694376565515995,
0.011754651553928852,
0.0002487337333150208,
0.006213237531483173,
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0.02243286557495594,
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0.014103084802627563,
0.03293798863887787,
-0.02302570454776287,
0.024284936487674713,
... |
<p><a href="http://stats.stackexchange.com/questions/86835/normality-assumption-in-linear-regression">Here</a> the misinterpretation of the assumption of normality in linear regression is discussed (that the 'normality' refers the the X and/or Y rather than the residuals), and the poster asks if it is possible to have ... | g63870 | [
0.005356422625482082,
-0.04142545908689499,
0.00047293902025558054,
0.025701234117150307,
-0.024864561855793,
0.00858778040856123,
0.011799688450992107,
0.05551505088806152,
0.0033149353694170713,
-0.0010438631288707256,
-0.00028354054666124284,
0.015576873905956745,
-0.04956592619419098,
... |
<p>Suppose that $X_1, X_2, X_3... $ is a Markov chain with the following transition matrix:</p>
<p>State:</p>
<pre>
| 1 2 3
--+-----------
1 |0.2 0.4 0.4
2 |0.5 0.0 0.5
3 |0.6 0.3 0.1
</pre>
<p>(forgive my attempt at a table if you can) </p>
<p>Calculate expectation and variance of $ S_n = X_1 + X_2 + X_3 + ... | g63871 | [
-0.04733442887663841,
0.03690262511372566,
-0.018557004630565643,
0.01776963286101818,
-0.05220543220639229,
-0.022600075230002403,
0.02699713222682476,
0.04857835918664932,
0.0006000418798066676,
-0.07538120448589325,
-0.052435994148254395,
0.03506346791982651,
-0.008939572609961033,
-0.0... |
<p>Im trying to create a one class SVM using libSVM. However whenever I run the svmpredict function it always return an accuracy of 0%. </p>
<pre><code>model = svmtrain(label,userProfile',('-s 2 -t 2 -c 1 -g .8'))
*
optimization finished, #iter = 6
obj = 4.792359, rho = 2.225069
nSV = 6, nBSV = 3
model =
Parame... | g21746 | [
-0.029489874839782715,
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0.010881446301937103,
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0.04509545490145683,
0.0... |
<p><img src="http://i.stack.imgur.com/SeF6U.jpg" alt="enter image description here"></p>
<p>I ran a command of rvf plot .
Does this graph show no heteroskedasticity?</p> | g49686 | [
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<p>I am working on the associative vocabulary data base. My sample size is 40 stimuli and the variables are frequencies of answers of different types (each variable is one type of answer). Out of six variables, three of them are distributed normally and the other three are not. I was thinking of using Friedman Test to ... | g63872 | [
0.005674320738762617,
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0.01676318049430847,
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0.0... |
<p>Is there a way to determine which features/variables of the dataset are the most important/dominant within a kmeans cluster solution generated via R?</p> | g63873 | [
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... |
<p>What are the various methods used for binary classification other than logistic regression? </p>
<p>What are the advantages of logistic reg. model in developing Propensity score w.r.t. other methods?</p>
<p>Actually I have been asked why? I backed it by saying its binary classification, so logit is perfect. Then I... | g63874 | [
0.03505491465330124,
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0.03331752121448517,
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0.0935211330652237,
0.0097... |
<p>Let $X$ and $Y$ be random variables with finite means $\mu_X$ and $\mu_Y,$ finite variances $\sigma_X^2$ and $\sigma_Y^2,$ and correlation $\rho.$ Let $A$ be the event that $X \leq \mu_X + k\sigma_X$ and $Y \leq \mu_Y + k\sigma_Y,$ where $k \gt 1.$ Using the one-sided univariate Chebyshev inequality, I can find this... | g63875 | [
-0.0062099481001496315,
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0.005911723244935274,
0.035591740161180496,
-0.01731390319764614... |
<p>As i know, PCA and PLS are two famous methods of dimension reduction
Could you please name for other
(neural network is it useful)?</p> | g63876 | [
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0.06255972385406494,
0.03... |
<p>For unweighted variance
$$\text{Var}(X):=\frac{1}{n}\sum_i(x_i - \mu)^2$$
there exists the bias corrected sample variance, when the mean was estimated from the same data:
$$\text{Var}(X):=\frac{1}{n-1}\sum_i(x_i - E[X])^2$$</p>
<p>I'm looking into weighted mean and variance, and wondering what the appropriate bias ... | g44816 | [
0.004583058413118124,
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0.01790015399456024,
0.04532249644398689,
0.01729697920382023,
0... |
<p>I'm new to statistics and have a query: </p>
<p>I have been given a scenario:
An experimenter set out to test the hypothesis that high-drive participants would be able to learn a simple task much more quickly than would low-drive participants. That hypothesis further stated that on a difficult task the opposite wou... | g63877 | [
0.01982244662940502,
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<p>I have made non-stationary data stationary by differencing at lag 1 and then differencing the differences at lag 11. The data values for months 1/06 through 6/11 are in an Excel file at <a href="https://rapidshare.com/files/3190310580/data.xls" rel="nofollow">https://rapidshare.com/files/3190310580/data.xls</a>, re... | g37790 | [
0.026411859318614006,
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0.07411208003759384,
0.06553278863430023,
-0.0... |
<p>I was wondering if there are any well-established or <strong>known low-dimensional <a href="http://en.wikipedia.org/wiki/Features_%28pattern_recognition%29" rel="nofollow">descriptors</a></strong> (i.e. <strong>heuristics or features</strong>) for the problem of discriminating periodic 1D signals from aperiodic ones... | g63878 | [
0.0268726609647274,
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0.042... |
<p>I want to conduct a poll on the quality of a product containing several questions with five possible answers:</p>
<ol>
<li>Very poor</li>
<li>Poor</li>
<li>OK / No opinion</li>
<li>Good</li>
<li>Very good</li>
</ol>
<p>A colleague has advised me to ditch option 3 (OK / No opinion) to force people to choose.</p>
<... | g21758 | [
0.013868676498532295,
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0.025926737114787102,
0.033388543874025345,
-0.02029346115887165,
-0.00029825110686942935... |
<p>Let us say we have some demographic time series data which tells us how many hours people spend in front of a computer screen each day, grouped by age and gender:</p>
<pre><code>set.seed(42)
dates = seq(as.Date("2011/1/1"), by="day", length.out = 100)
male.age1 = round(runif(100, min = 1, max = 10))
female.age1 = r... | g63879 | [
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0.0011285344371572137,
0.023121122270822525,
0.019822807982563972,
0.051112815737724304,... |
<p>I´m using the <code>pam()</code> R function to perform clustering. As far as I know, the <code>pamk()</code> function serves as a wrapper to <code>pam()</code>, and evaluates the optimal number of clusters. However, using the same data and parameters I get different results.</p>
<p>For example, calling <code>pamk()... | g44827 | [
0.04725908860564232,
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0.007279384881258011,
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0.020908651873469353,
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-0.06880457699298859,
-0.013280441984534264,
0.02705243043601513,
0.10290093719959259,
0.03... |
<p>I've got some data that has this basic shape (using R):</p>
<pre><code>df <- data.frame(group=sample(LETTERS, 500, T, log(2:27)),
type=sample(c("x","y"), 500, T, c(.4,.6)),
value=sample(0:20, 500, T))
</code></pre>
<p>I want to investigate the ratios between <code>x</code> and... | g63880 | [
-0.03351227566599846,
-0.005237225908786058,
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0.020362025126814842,
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0.029281217604875565,
0.035428546369075775,
0.0641297847032547,
0.... |
<p>Consider the following picture representing the experimental data sequence obtained by two 1D-sensors (each point of the sequence is plotted on XY plane according to the respective sensor reading):<br>
<img src="http://i.stack.imgur.com/U6fWb.png" alt="experimental raw data"></p>
<p>It's visually obvious that two m... | g63881 | [
-0.02938334457576275,
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0.008107388392090797,
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0.0019316134275868535,
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0.06724944710731506,
0.003216350683942437,
0.00958081241697073,
0.0007390966056846082,
0.02442007139325142,
-0.027225419878959656,
0.029997963458299637,
0.028... |
<p>I have multiple square matrices represent the relations between members of a club.
Is there any statistical method to represent these metrices as one matrix.</p> | g63882 | [
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0.0017056796932592988,
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0.03512362018227577,
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0.0004716477124020457,
0.032183632254600525,
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0.05142062157392502,
-0... |
<p>You conduct a case-control study of elevated cholesterol and myocardial infarction (MI). Of 20 MI cases, 10 had elevated cholesterol. Of 30 healthy controls, 10 had elevated cholesterol. These results give an odds ratio (OR) of 2.0, with a 95% confidence interval (CI) $ = [0.6-6.4]$.</p>
<p>Interpret the CI?</p> | g63883 | [
0.04877699911594391,
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0.07713764905929565,
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0.05326768383383751,
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0.013740983791649342,
-0.0... |
<p>I'm wondering how to compare the predictions of three different models - a logit, a probit and a linear probability model - when predicting a binary outcome. I'm currently working with simulated data, so I have access to both the latent variable $y$ and the binary outcome $Y$ with $\Pr(Y=1)=y$</p>
<p>I'm under the ... | g21761 | [
0.004574117250740528,
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0.026015441864728928,
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0.026041904464364052,
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0.02545767091214657,
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0.04255138337612152,
-... |
<p>I am doing an experiment whereby I have 4 different conditions. Within each condition, I do 4-7 technical replicates (cell counts in 4-7 high powered fields). I have also repeated the experiment 3 times (3 biological replicate (rats)). What test will compare the 4 different conditions, but will also take into acc... | g63884 | [
0.04071507602930069,
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0.003982160706073046,
0.00883996021002531,
0.033415891230106354,
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0.007832246832549572,
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... |
<p><a href="http://en.wikipedia.org/wiki/Good%E2%80%93Turing_frequency_estimation" rel="nofollow">Good–Turing frequency estimation</a> is a smoothing estimator for estimating a multinomial distribution. It seems very convoluted.</p>
<ol>
<li>From mathematical statistics point of view, what is the rationale
behind the... | g63885 | [
0.055468253791332245,
0.01384005043655634,
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0.018739590421319008,
0.01842123456299305,
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-0.006425004918128252,
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0.012356414459645748,
0.039703093469142914,
0.09... |
<p>Overlapping data are often present in time-series analysis and the academic studies mention about Heteroskedasticity and Autocovariance Consistent (HAC) estimators to solve this isssue, such as Newey-West (Harri & Brorsen, 2009). I would like to know if Cochrane-Orcutt estimator could also be employed with overl... | g63886 | [
0.013945013284683228,
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0.012182612903416157,
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0.04126662015914917,
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0.06864094734191895,
0.08282160013914108,
-0.0010293296072632074,
0.025663213804364204,
0... |
<p>Let $U$ be a random variable uniformly distributed over (0,1). Compute the conditional distribution of U given that $U>a$</p>
<p>The solution says:</p>
<p>$P(U > s | U > t) = \frac{P(U > s)}{P(U > t)}$</p>
<p>Here I'm confused why the conditional probability translates into the fraction on the righ... | g63887 | [
0.051349807530641556,
-0.01984231546521187,
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0.01627613790333271,
0.023301510140299797,
0.00036... |
<p>I've just began looking into survival analyses, and I'm having some difficulty interpreting the results. </p>
<p>I have a model linear regression model where time ~ x1 * x2 * x3... x9, this model seems to fit well (adjusted R${^2}$ of ~0.9) however it was suggested that survival analyses may be a better direction.<... | g63888 | [
-0.01438403595238924,
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0.02989102713763714,
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0.03407483920454979,
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0.06722068786621094,
0.02... |
<p>I am running segmented regression using the R package 'segmented'. The original binomial logistic regression has two coefficients, approach_km (continuous), and sea (dichotomous) that explain the probability of the dependent variable occurring. I am interested in investigating if there is a break-point in the regres... | g63889 | [
-0.02056724950671196,
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0.0024047656916081905,
0.01916559226810932,
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0.046300116926431656,
0.026132900267839432,
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-0.015314895659685135,
-0.04183611273765564,
0.026215527206659317,
0.07861088961362839,
-0... |
<p>I am trying to wrap my head around splines and the concept of basis functions using the <em>Elements of Statistical Learning</em>. I understand that the goal is to find polynomials that are continuous at first and second derivatives. However, following the picture below, I don't understand whether </p>
<ul>
<li>a) ... | g21767 | [
0.030873680487275124,
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0.03924793377518654,
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0.08724063634872437,
0.029522370547056198,
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-0.04155107960104942,
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0.003704620525240898,
0.055339325219392776,
-0.... |
<p>What are the best methods to <em>accurately</em> generate random integers distributed according to a power law? The probability of getting $k$ ($k=1,2,\ldots$) should be equal to $p_k = k^{-\gamma} / \zeta(\gamma)$ and the method should work well for any $\gamma > 1$.</p>
<p>I can see two naive approaches:</p>
... | g21769 | [
0.024129897356033325,
-0.051373228430747986,
-0.01705092377960682,
-0.007555817719548941,
-0.0382826030254364,
-0.017189722508192062,
-0.04926995187997818,
0.031658194959163666,
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0.0006013737875036895,
0.038232337683439255,
-0.03818325325846672,
0.08772958815097809,
0.... |
<p>Two cyclists are racing over 50 (for example) km. Cyclist A has an estimated speed of X km per hour, cyclist B has an estimated speed of Y km per hour. Both of these estimated speeds are the means of two normal curves of the true actual speed. </p>
<p>The two normal curves overlap. If I know the estimated speeds of... | g63890 | [
0.011466572992503643,
0.030138641595840454,
0.025368966162204742,
0.04219217970967293,
-0.03507858142256737,
0.017132004722952843,
0.04402149096131325,
0.000018407710740575567,
-0.05690450966358185,
0.007722077891230583,
0.0157726239413023,
-0.013584970496594906,
0.04848052188754082,
-0.03... |
<p>I want to use R to build an ordered logistic regression model and to measures its performance.
My goal is to predict whether an athlete will get gold, silver or bronze.</p>
<p>I started with logistic regression where the number of available categories is two, e.g. won and lost.</p>
<pre><code>str(DATA$dependent_va... | g21770 | [
-0.044943325221538544,
-0.029455415904521942,
-0.00818224623799324,
-0.01854727976024151,
0.01610514521598816,
-0.033137451857328415,
0.016507588326931,
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-0.05493992939591408,
-0.023406265303492546,
0.06336720287799835,
0.037265047430992126,
-0.0... |
<p>I know basically how to express PCA (Principal component analysis) mathematicaly, but I would like to know steps that should be used for factor analysis.</p>
<pre><code>Let us consider some matrix, for instance
A=[3 1 -1;2 4 0;4 -2 -5;11 22 20]
A =
3 1 -1
2 4 0
... | g63891 | [
0.025138651952147484,
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0.013898230157792568,
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0.02565658465027809,
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0.1140439584851265,
0.050166286528110504,
0.003931194543838501,
0.022048838436603546,
-0.031349118798971176,
0.02539302036166191,
0.04998370260000229,
0.025167... |
<p>I'm using R and the library TraMineR to do sequence analysis on social science data. I need to use the extractSeqFromW function, but I have problems opening the file even if they are exactly in that directory.</p>
<pre><code>source("extractSeqFromW.R")
sla <- extractSeqFromW("Users/emanuelastruffolino/Desktop/S... | g42856 | [
-0.03394923359155655,
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0.01826944574713707,
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0.05100725218653679,
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-0.02913692221045494,
0.011954797431826591,
-0.06075957417488098,
0.04370063170790672,
0.009... |
<p>Having read from the internet that <code>glmer</code> and <code>lmer</code> are similar thing (correct me if I am wrong), just <code>glmer</code> need to state the family, I wonder if I state the family for <code>glmer</code> as "gaussian", can I replicate the same result as <code>lmer</code> does? </p>
<blockquote... | g21773 | [
-0.006881227251142263,
-0.0027115102857351303,
0.012745141051709652,
-0.06715399771928787,
0.00023713373229838908,
-0.005333720240741968,
-0.03465506434440613,
-0.010776186361908913,
-0.051645271480083466,
-0.051996804773807526,
-0.010972821153700352,
0.03265261650085449,
0.07905938476324081... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/39134/not-sure-how-to-work-out-ssg-and-sse-on-anova-table">Not sure how to work out SSG and SSE on ANOVA table</a> </p>
</blockquote>
<p>I have a table that is:</p>
<p>$$
\begin{matrix} & \mathrm{Tyre... | g41198 | [
-0.018636757507920265,
0.030806560069322586,
-0.017711838707327843,
-0.0302945114672184,
-0.004707240965217352,
-0.007667727302759886,
0.056789182126522064,
0.04287992790341377,
-0.02580852620303631,
0.025640318170189857,
-0.03394540026783943,
0.012398123741149902,
0.0019161032978445292,
-... |
<p>I have a data set that is composed of the age an industrial machine part is when it fails (x variable) and the part's width in nanometers (y variable) at the time when it fails. The data looks something like this:</p>
<pre><code>age (days) width (nm)
10 100
18 88
36 45
... ... | g21777 | [
0.015873808413743973,
-0.031903840601444244,
-0.01230166107416153,
-0.06455009430646896,
-0.03963509202003479,
0.025178320705890656,
0.010257252492010593,
-0.02429231069982052,
-0.0440591424703598,
-0.0314207561314106,
0.026164455339312553,
0.014636410400271416,
0.02772664651274681,
-0.032... |
<p>The history of many fields of science can be divided into a small number of time intervals that often begin with some important discovery.</p>
<p>But I have never seen something similar in timeline of statistics.</p>
<p>Obviously, there are some important dates that can be considered as starting points of a new pe... | g63892 | [
0.06721862405538559,
0.03897213190793991,
-0.00009187526302412152,
-0.0007219031685963273,
0.0035307900980114937,
-0.00313724298030138,
0.021506773307919502,
-0.002683068625628948,
0.036664869636297226,
-0.02568511851131916,
-0.002082168823108077,
0.017667345702648163,
0.07118966430425644,
... |
<p>I have total of 9 time series data. I'm basically using 8 variables as my X and 1 variable as Y. I've tried VAR model today but I don't see ANYTHING. However, when I do linear regression, all of the variables are significant, and p value of the model is less than 0.01 %. Is this result indicates something? </p> | g21779 | [
0.014001641422510147,
-0.008525645360350609,
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-0.03239389881491661,
0.049117326736450195,
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0.006619960069656372,
0.02054334618151188,
0.00878873560577631,
-0.042516931891441345,
0.003925831522792578,
0.019259877502918243,
0.0028394798282533884,
0.... |
<p>I am comparing supervised vs unsupervised method. I have computed entropy from the confusion matrix of the 10-fold crossvalidated output. I have also applied external criteria to unsupervised methods and computed entropy from it. Next checked its significance. I was wondering when I compare supervised entropy vs uns... | g63893 | [
0.037153929471969604,
-0.013850743882358074,
0.0120660699903965,
-0.06416351348161697,
0.02182185649871826,
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0.03374370187520981,
0.053793616592884064,
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-0.013202954083681107,
0.010399597696959972,
0.01768406480550766,
0.06773010641336441,
-0.01142... |
<p>I performed with R an ANOVA and I got significant differences. However when checking which pairs were significantly different using the Tukey's procedure
I did not get any of them.
How can this be possible?</p>
<p>Here is the code:</p>
<pre><code>fit5_snow<- lm(Response ~ Stimulus, data=audio_snow)
anova(fit5_s... | g49322 | [
-0.006814651191234589,
-0.044637277722358704,
-0.011115693487226963,
-0.012024751864373684,
0.017437569797039032,
0.011157065629959106,
0.10376278311014175,
0.025545621290802956,
-0.03216533735394478,
-0.0018408459145575762,
-0.02749551832675934,
0.008627536706626415,
0.03332393988966942,
... |
<p>Necessary advance apologies: I am not a statistician, so I hope I am able to make my question as clear as possible.</p>
<p>I have a price timeseries... say, something like this, but much more granular:</p>
<p><img src="http://i.stack.imgur.com/RNJ3E.jpg" alt="enter image description here"></p>
<p>And I'm looking ... | g63894 | [
0.01934630796313286,
0.022183861583471298,
-0.04029598459601402,
-0.004307725001126528,
0.024811435490846634,
-0.09828086942434311,
0.03478236868977547,
-0.0568886324763298,
-0.009774131700396538,
0.025212788954377174,
-0.00638955645263195,
0.07258500903844833,
0.09643401950597763,
-0.0150... |
<p>I have a multivariate problem. I have energy usage, max. temprature, and days. I want to predict load which is energy usage for various consumers. LM does not work as it is not linear. I am planning to use multivariate ARIMA. I want to implement it in R. I will appreciate if you could suggest some good pointers.</p> | g63895 | [
0.005366798955947161,
-0.030865421518683434,
-0.0007445724331773818,
-0.03723243623971939,
-0.06372787803411484,
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-0.013023904524743557,
-0.027665741741657257,
-0.05801492556929588,
0.04838932305574417,
0.06144251674413681,
-0.0024269274435937405,
0.06073068082332611,
... |
<p>Could someone recommend some well-maintained and up-to-date libraries for working with probabilistic graphical models?</p>
<p>I noticed that there are some libraries for R listed <a href="http://cran.r-project.org/web/views/gR.html" rel="nofollow">here</a> and <a href="http://staff.science.uva.nl/~jmooij1/libDAI/" ... | g63896 | [
-0.015242047607898712,
0.0008101636194624007,
0.029880734160542488,
-0.05043310672044754,
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0.030400989577174187,
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-0.009464239701628685,
0.07098388671875,
-0.02973102033138275,
0.08779263496398926,
0.022... |
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