question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>We want to add a forecasting tool to our website -- it would draw off a historical database and users can choose the model (Box Jenkins, Simple Linear Regression, etc.), confidence interval and play what-if. Is anyone aware of such package we can plug into our website?</p> | g62610 | [
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<p>What software (or method) can I use to determine correlations between any sets of variables and results?</p>
<p><strong>Background:</strong>
I would like to analyze sets of our archived data over several years. Knowledge of the product tested often leads to some obvious correlations (ie: fuel efficiency peaks at a... | g19757 | [
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<p>I have one variable that attains a certain value (between 0 and 1), about 1000 observations and each belongs to one (and only one) of fifteen groups. Now I would like to reduce the number of groups to two or three by combining them. It is important that all the data within a given group in the former division will s... | g62611 | [
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<p>If $X_1,X_2$ constitute a random sample of size n=2 from a Poisson Population show that the mean of the sample is a sufficient estimator of the parameter $\lambda$ . </p>
<p>Since the sum of Poissons is also Poisson with parameter $\lambda+\lambda=2\lambda$<br>
Then $E[Y]=2\lambda$. where Y constitute of two Poi... | g62612 | [
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<p>I have a multivariate regression model $\mathbf{Y}$ = $\mathbf{XB}$ + $\mathbf{E}$ where $\mathbf{Y}$ is $n \times m$. </p>
<p>In my case $\mathbf{n < m}$, the number of columns in $\mathbf{Y}$ is greater than the number of rows. Is it still possible to do multivariate hypothesis testing with a model like this ... | g62613 | [
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<p>I have a dataset relating two variables to a result, as shown in the image below.</p>
<p><img src="http://i.stack.imgur.com/PLoy1.jpg" alt="image showing 2 variables related to a result"></p>
<p>In the image Variable 1 is held constant, and plotted against different values of Variable 2, and the result is shown. I... | g62614 | [
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<p>I am new to Regression and R. I know that polynomial functions are used when a regression model does not fit data (underfitting), but I want to know which degree of polynomial should be used? I also want to know that if a regression model uses multiple variables (e.g., <code>y ~ x1+x2+x3+x4</code>) then do I need a ... | g19760 | [
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<p>I have an experiment which is executed on hundreds of computers distributed all over the world that measures the occurences of certain events. The events each depend on one another so I can order them in increasing order and then calculate the time difference.</p>
<p>The events should be exponentially distributed b... | g19761 | [
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<p>I asked participants in an experiment the same question once before and once after the experiment, to see the effect of the experiment on the answer. The answers were given on a 5-point scale. To me the change, so the difference between the before and the after answer to the question, is interesting. So I want to se... | g62615 | [
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<p>I have a household travel survey where information about travel characteristics were obtained from a sample of households. The respondents were given a diary and a GPS device to log their trips for a single day. However, for some respondents additional travel days were collected from the GPS device. Because the addi... | g62616 | [
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<p>this is kinda homeworkish so I don't want a full solution I just want some input. </p>
<p>I have this data set
<img src="http://i.stack.imgur.com/ObZgv.png" alt="dataset"></p>
<p>And I want to transform the data (with a rbf Kernel?) in order to be able to do a simple linear ridge-classifier. </p>
<p>I know I can... | g62617 | [
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<p>There is a simple regression model table I was looking at in a textbook with IQ values grouped into 5 intervals and each group had an N number associated with it. There was also information given about the residuals for each group (mean and variance for the residuals).
e.g For the < 75 IQ group, N = 23, Mean of ... | g62618 | [
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<p>I'm running a 2x2x2x2x2 mixed model ANOVA (on SPSS v21) for my study and found two 4-way interactions, one 5-way interactions and a couple of 3-way interactions. Whilst I understand how to interpret a 3-way ANOVA. I'm having quite a hard time trying to interpret the 4/5-way interactions. </p>
<p>My variables are:</... | g62619 | [
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<p>Given data points $x_i$ in $\mathbb{R}^d$ with function values $f_i$,
one can estimate the function at a given $x$ by
$\ \ \ \ \text{f}_{est}( x ) = \frac {\sum { w_i f_i }} {\sum { w_i }}$
with $w_i = k( |x - x_i| )$.<br>
Here $k$() is a kernel function, often Gaussian.
See also <a href="http://en.wikipedia.org/wi... | g62620 | [
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<p>I have a jar with white and black balls. Total number of balls in the jar is 100000. I want to estimate the proportion of white balls. My constraint is that the sample size for estimation should be low, lets assume 500 balls. I am debating between two approaches.</p>
<ol>
<li>Draw a single sample of 500 balls, $\ha... | g62621 | [
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<p>I have two groups of patients who underwent a surgery using method A or method B. The first group are patients who were operated in 1980's and 1990's only with method A. The second group are patients operated recently with mostly method B, but also in some cases A. In addition to that, I have various variables about... | g19765 | [
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<p>My question is: how one derives a Weibull distribution for a lifetime of a system where parts are wearing out with time?</p>
<p>Provided that this is the lifetime analysis with aging is the main application of a Weibull distribution, I was surprised not to find a derivation why specifically this distribution and no... | g62622 | [
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<p>The literature in MCMC and LBP never refer to the fact that the two methods look (on expectation) exactly the same. To illustrate, first consider a simple Ising model, that is, a graphical model where all the variables are boolean. We can denote these variables as $\{ X_i | X \in \{0,1\}, i \in (1,...,n)\}$ and we... | g38824 | [
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<p>After gathering data, we compute score of any Likert (summative) scale (previously identified as factor in factor analysis) by adding up its individual item scores (and maybe dividing the sum by the number of items to get the mean score). In that calculation, we assume that every item in the scale has equal weight. ... | g49241 | [
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<p>Suppose you have SAS code as follows. This is from <a href="http://www.ats.ucla.edu/stat/sas/faq/anovmix1.htm" rel="nofollow">http://www.ats.ucla.edu/stat/sas/faq/anovmix1.htm</a>. </p>
<pre><code> PROC MIXED DATA=long;
CLASS sub group trial;
MODEL dv = group trial group*trial;
REPEATED trial / SUBJECT=sub TY... | g38827 | [
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<p>I have a dataset with 8000 clusters and 4 million observations. Unfortunately my statistical software, Stata, runs rather slowly when using its panel data function for logistic regression: <code>xtlogit</code>, even with a 10% subsample.</p>
<p>However, when using the nonpanel <code>logit</code> function results ap... | g49861 | [
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<blockquote>
<p>The degrees of freedom in a multiple regression equals $N-k-1$, where $k$ is the number of variables. </p>
</blockquote>
<p>Does $k$ include the response variable (i.e., $Y$)? For example, in the model $Y = B_0 + B_1X_1 + B_2X_2$, then does $k = 3$ (i.e., 1 df each for $Y$, $X_1$, & $X_2$)? </p> | g39681 | [
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<p>I am designing a points-scored test. There is a limit on the maximum amount of points possible, as well as on the fewest amount of points possible. I have had a test group take the test and graphed their results, which form a lopsided bell curve or sorts. I am trying to figure out what kind of distribution would be ... | g10137 | [
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<p>I have downloaded my Latitude location history from Google for the time of about three years and now I'd like to, for starters, visualize where I've been.</p>
<p>It turns out that the history contains some outliers. For example, I have been located in China or in Africa, where in fact I haven't been. Other outliers... | g531 | [
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<p>I have two very important things to know. Can anyone help?</p>
<h3>Question-1</h3>
<p>If I have three categorical dependent variables and a continuous dependent variable, which are correlated (or associated), then if I conduct separate regressions with each dependent variable instead of a multivariate regression, ... | g38839 | [
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<p>I'm trying to implement basic gradient descent and I'm testing it with a hinge loss function i.e. $l_{\text{hinge}} = \max(0,1-y\ \boldsymbol{x}\cdot\boldsymbol{w})$. However, I'm confused about the gradient of the hinge loss. I'm under the impression that it is </p>
<p>$$
\frac{\partial }{\partial w}l_{\text{hinge... | g37668 | [
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<p>from what I can tell, PASW v.18 (the new version of SPSS) only gives you the p value of nonparametric tests. I am calculating Kruskal Wallis and Mann Whitney tests, and need to report the test statistic, not just p. Can someone please help?
Thanks!</p> | g62623 | [
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<p>I am thinking of using <a href="http://www.mathworks.com/matlabcentral/fileexchange/14034-kernel-density-estimator" rel="nofollow">this code</a> in a Monte Carlo routine to generate Kernel Density Estimates for subsequent use in a Naive Bayes Classifier <a href="http://stats.stackexchange.com/questions/4298/use-of-k... | g62624 | [
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<p>I want to cluster data that contains binary variables, exponentially distributed (power law) variables, and normally distributed variables. I'm considering preprocessing the data in the following way and wondering whether it's reasonable.</p>
<p>1) shift the binary variables so that they have mean zero. no rescalin... | g62625 | [
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<p>I'm doing some some analysis of an arbitrary string of text, modelling it as a Markov chain where the state is simply the value of the previous character. Call the current character <code>c</code> and the previous character <code>p</code>; then it is trivial to calculate <code>P(c | p)</code> for the given sample te... | g62626 | [
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<p>Suppose I have a data set with the following structure:</p>
<p>Each row of the data set indexes a town. The first column/feature variable is the total population while the other feature variables include the count of people who own various items (one feature variable for cars, one for home appliances, etc.), while ... | g62627 | [
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-0.008122613653540611,
0.044281214475631714,
-0.05894606560468674,
0.010626900009810925,
-0.0036665601655840874,
0.042438652366399765,
0.040579408407211304,
-... |
<p>Are there any open-source Java implementations of lasso or least angles regression?</p>
<p>Pure Java code would be best, but clean implementations in other languages would also be of interest. I am already aware of the existence of a variety of R packages than can do lasso/LAR fits.</p>
<p>Thanks.</p> | g62628 | [
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0.016188913956284523,
0.045194484293460846,
0.059461675584316254,
... |
<p>I have run a factorial type test in a processing plant and have run a forward and backward step regression in R. </p>
<p>How can I use the regression results and the anova created from the regression to know what percent of the measured variation of the dependent variable was caused by the purposeful manipulation o... | g19777 | [
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0.05547678470611572,
0.005653435364365578,
0.035... |
<p>If I have a relationship:</p>
<p>$ y_t = a + \theta b_t \epsilon_t,$</p>
<p>where I observe $y_t$ and $b_t$. $a$ is a known parameter, $\theta$ is an unknown parameter with prior distribution at time $t$: $\theta \sim logN(\mu_t, \sigma_t^2)$, and $\epsilon_t$ is an IID random variable with distribution: $\epsilon... | g62629 | [
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0.019502917304635048,
0.018475603312253952,
0.0387408584356308,
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0.01... |
<p>I'm implementing a bayesian Hidden markov model. I now face the problem of how to choose the number of components. I have two problems:
1) which index is better to use?
2) suppose i decide to use the BIC and that I estimates the model with an MCMC procedure. Have I to compute the BIC for each posterior sample and th... | g62630 | [
0.0004733037785626948,
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0.02852555923163891,
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0.0... |
<p>Given a generic classification model
$y=f(x_1,x_2,..,x_p)$ where $y\in \left\lbrace 0,1 \right\rbrace$ is it possible to compute the odds ratio for each variable? </p>
<p>A theoretical explanation and an example with R code would be the best answer</p> | g62631 | [
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0.024541804566979408,
0.04895792901515961,
0.03421574458479881,
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<p>I have a list of items that represent cells, now i query each cell value to get a set of possible categories that this cell might belong to, these categories are weighted. For Example:</p>
<pre><code>Microsoft is: {Software=83.543266, Video Game Platform=132.297455, Degree=71.624733, Organization=208.17038, Program... | g19779 | [
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<p>Is there a standard approach for testing goodness-of-fit to a probability distribution when the samples are independent but not identically distributed? In other words, given the data $\{\{x_1, y_1\}, \{x_2, y_2\},..., \{x_n, y_n\}\}$ and the candidate density function $f(x;y)$, what is an accepted approach for test... | g62632 | [
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0.009708540514111519,
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0.026054030284285545,
... |
<p>I am getting astronomically high p-values for all the coefficients in a logistic regression model. I am not sure why they are so high:</p>
<ul>
<li>0.7096 </li>
<li>0.4441 </li>
<li>0.9783 </li>
<li>0.7826 </li>
<li>0.6890 </li>
<li>0.7538 </li>
<li>0.8017 </li>
<li>0.9332 </li>
<li>0.9564</li>
</ul>
<p>I honestly... | g19781 | [
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0.004725622478872538,
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0.0035271102096885443,
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0.03461895138025284,
0.039474643766880035,
-... |
<p>In cognitive psychology, it has been argued that the learning curve of a skill follows the power function, in which the practice of the skill yields progressively smaller decrements in error. I want to test this hypothesis with the data I have, and to do this I need to fit a power law function to the data.</p>
<p>I... | g19782 | [
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0.0005167054478079081,
0.055537719279527664,... |
<p>In simple linear regression, where the model</p>
<p>$$\mathbb{E}(y) = \beta_0 + \beta_1 x$$</p>
<p>is estimated using least squares (and the errors are assumed iid of mean $0$), why is the covariance between the mean response $\bar{y}$ and the estimated slope $\hat{\beta_1}$ equal to zero?</p> | g49649 | [
0.05361160635948181,
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0.016890788450837135,
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... |
<p>Let's say that you're fitting a model to predict some score as a linear function of two categorical inputs. Something like the following data set:</p>
<pre><code>score x y
---------------------
46.12 A B
42.61 A F
39.14 B A
57.72 B C
48.65 B D
56.29 B E
45.45 B F
42.43 C B
52.68 ... | g304 | [
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0.00880296528339386,
0.04415363818407059,
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0.006523661781102419,
0.024345088750123978,
0.02398381382226944,
0.0806359350681305,
0.0346... |
<p>I am writing an implementation of the EM algorithm to estimate parameters in a GLMM in R. My model is $$y_{ij}|\alpha_i \sim Bin(1,p_{ij})\textrm{, where }logit(p_{ij}) = \mu + \alpha_i \textrm{ and } \alpha_i \,\,iid \sim N(0,\sigma^2).$$ In other words, my data has a binary response that can be modeled with a fix... | g19788 | [
0.004122595302760601,
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0.04167400673031807,
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0.012852908112108707,
0.0... |
<p>I got the following outcome. I am confused with the interpretation. When I consider RSS then model 2 is better than model 1. What does that high p value mean? Does in influence my conclusion?? </p>
<blockquote>
<p>anova(reg4.3,reg4.4, test="Chisq")</p>
</blockquote>
<pre><code>Analysis of Variance Table
Model 1... | g62633 | [
0.002078673802316189,
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0.04035399109125137,
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0.0755813792347908,
0.03800699859857559,
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-0.04369547218084335,
-0.04183333367109299,
0.061617739498615265,
0.013374763540923595,
-... |
<p>Suppose I have $N$ independent random numbers with a uniform distribution in $[+1, -1]$. Suppose I take the discrete Fourier transform of these numbers. What would the probability distribution of each frequency coefficient be?</p>
<p>Each frequency coefficient is the weighted sum of $N$ independent random numbers w... | g62634 | [
-0.015092582441866398,
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-0.06995696574449539,
-0.06099679321050644,
-0.005064294673502445,
0.026513513177633286,
0.013... |
<p>When doing research in Economy, one frequently needs to verify theoretical conclusions on real data. What are reliable data sources to use and cite? I am mainly interested in sources that provide various statistical data such as GDP, population, CPI, PPI etc.</p>
<p><strong>EDIT:</strong>
Here's an aggregation of t... | g19791 | [
0.0539839006960392,
0.022730639204382896,
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0.011560090817511082,
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0.013243873603641987,
0.05882212519645691,
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0.07916184514760971,
-0.0... |
<p>I'm trying to understand the concept of the <a href="http://en.wikipedia.org/wiki/Expected_value">expected value</a>.
Especially, what bothers me is the expected value for discrete random variables. I will try to formulate it by examples:</p>
<ul>
<li><p>The expected value when throwing a six-sided die is $E(X) = 3... | g19794 | [
-0.029644912108778954,
0.040771644562482834,
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0.011020343750715256,
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0.029775120317935944,
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-0.08125250786542892,
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-0.01213841326534748,
0.04744783416390419,
... |
<p>Physicist here with a naive question,</p>
<p>I've got a data set (points $x_i,y(x_i),i\in \mathbb N$) and two different smooth curves $f(x),g(x)$ from my simulation. I can't quite judge with my eye which one fits better with my eyes only. What are some tools to make a judgement here?</p>
<p>My initial thought is t... | g62635 | [
0.06896648555994034,
0.017318908125162125,
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0.024642309173941612,
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-0.001946933101862669,
0.02669430524110794,
0.04887297376990318,
0.08998294919729233,
-0.00... |
<p>Say I have the following sample:</p>
<pre><code>-0.38848247;0.21655804;-1.08211969;0.00369104;0.0993393;0.25531731;1.40574444;-1.80271115;-0.58780605;-0.35026458;0.67197532;-1.29654652;-0.58874467;-0.4004176;1.46242829;0.83946654;-0.24861179;-1.604154;1.53555232;1.45589014;-0.52092604;1.65504054;0.12854317;1.667712... | g62636 | [
-0.027599992230534554,
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0.011651108041405678,
-0.06650407612323761,
-0.0007310931687243283,
-0.039886474609375,
0.026895176619291306,
-0.012149782851338387,
0.003914565779268742,
0.0032465059775859118,
-0.03662336245179176,
0.012303231284022331,
0.061547067016363144,
0... |
<p>My model has seven independent variables and one dependent variable. Each are subscales for a 5 point likert scale questionairre. I tested each variable data and they are all non normal. I did spearman correlation and identified several significant correlations. I tried testing the model using linear regression but ... | g37429 | [
0.03486053645610809,
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0.006781429052352905,
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0.014893559738993645,
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0... |
<p>Label switching (i.e., the posterior distribution is invariant to switching component labels) is a problematic issue when using MCMC to estimate mixture models. </p>
<ol>
<li><p>Is there a standard (as in widely accepted) methodology to deal with the issue?</p></li>
<li><p>If there is no standard approach then what... | g62637 | [
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0.00405638013035059,
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0.023882433772087097,
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0.04681174457073212,
0.05096826329827309,
0.007014700211584568,
0.05277671292424202,
0.02... |
<p>I really enjoy hearing simple explanations to complex problems. What is your favorite analogy or anecdote that explains a difficult statistical concept?</p>
<p>My favorite is <a href="http://www-stat.wharton.upenn.edu/~steele/Courses/434/434Context/Co-integration/Murray93DrunkAndDog.pdf">Murray's</a> explanation of... | g62638 | [
0.04276490584015846,
0.021960165351629257,
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0.005910366773605347,
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0.03666212409734726,
0.04340255260467529,
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0.022588394582271576,
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-0.06008319556713104,
0.027958013117313385,
-0.0... |
<p>I know this must be standard material, but I had difficulty in finding a proof in this form.</p>
<p>Let $e$ be a standard white Gaussian vector of size $N$. Let all the other matrices in the following be constant.</p>
<p>Let $v = Xy + e$, where $X$ is an $N\times L$ matrix and $y$ is an $N\times 1$ vector, and le... | g693 | [
0.021250475198030472,
0.007920293137431145,
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0.04083671048283577,
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0.05111782252788544,
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0.052336808294057846,
-0.017550615593791008,
-... |
<p>Is there a simple way to determine (other than by simulation) the expected standard deviation of a sample, when sampling from a population with known distribution, for example a normal distribution with mean 25 and standard deviation 5, but the samples are included/excluded if they fall within certain limits ? In pa... | g38869 | [
0.04305383563041687,
0.039705101400613785,
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0.03471596911549568,
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0.0016209473833441734,
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-0.036593858152627945,
-0.007481405511498451,
-0.008036740124225616,
-0.003986956086009741,
... |
<p>I am trying to train an Artificial Neural Network for classification. In the input layers, I have 402 neurons; the first 400 are binary, and the last two are floating points in the range -1 to 1. In the hidden layer I have 400 neurons, and in the output layer I have a single node which I want to represent values bet... | g62639 | [
0.011042976751923561,
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0.004140943754464388,
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0.056755997240543365,
0.07023176550865173,
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-0.025858314707875252,
-0.02875182032585144,
0.10646560043096542,
-0.0118830231949687,
-0.003... |
<p>I'm looking for the paper:</p>
<p><em>Streitberg and Rohmel (1986) <strong>Exact calculations for permutation and rank tests: an introduction to some recently published algorithms.</strong> Statist. Soft.Newsletter, 12, 10-17.</em></p>
<p>Google Scholar shows a citation, but not a link, and says that it's cited by... | g38870 | [
0.05703065171837807,
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0.019489916041493416,
0.016438284888863564,
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0.018139485269784927,
-0.004528272897005081,
-0.021519219502806664,
0.034397535026073456,
0... |
<p>I have a sample of data generated in <code>R</code> by <code>rnorm(50,0,1)</code>, so the data obviously takes on a normal distribution. However, <code>R</code> doesn't "know" this distributional information about the data.</p>
<p>Is there a method in <code>R</code> that can estimate what kind of distribution my sa... | g62640 | [
0.05426089093089104,
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-0.012109056115150452,
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0.027623375877738,
0.024886712431907654,
0.0... |
<p>I have a data set which consists of 1.Number of users, 2.Cpu usage, 3.Ram Usage, 4.Response time,</p>
<p>The way I understand it Number of users is my independent variable. Is there a way, a method, or a program to help me create a function that expresses Response time in terms of cpu usage, ram usage and number of... | g62641 | [
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0.056574106216430664,
0.023664958775043488,
0.0229018... |
<p>I'm facing the problem of visual tracking in computer vision. I have some observation (image blobs by background subtraction) produced by some moving object, and the task is to infer the state (position, velocity) of the object given the observation. I assume that each state depends only on the immediate predecessor... | g62642 | [
0.040168534964323044,
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0.010576111264526844,
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0.0003624113742262125,
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0.0... |
<p>I have a 'black box' model that outputs model predictions, but I don't know what actually goes on inside the model. I also have a bunch of data that I can pass through the model so that I can compare the predictions with actual results. Which interval would I use to bound most of the actual values around the predi... | g62643 | [
-0.020848698914051056,
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0.021864447742700577,
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0.004559656605124474,
0.03736080601811409,
0.07717981934547424,
-0.007... |
<p>I am trying to randomize 60 patients in two treatments (A and B) where age will be used as strata. Since we don't know how many patients of each stratum will enter the study I have created two randomization lists of 15 blocks each (4 patients at each block). </p>
<p>Since treatment allocation should be 1:1 (thus 30... | g4049 | [
-0.036833085119724274,
0.0072994111105799675,
-0.007830760441720486,
-0.04401466250419617,
-0.0386468768119812,
0.023580070585012436,
0.0043203020468354225,
0.022345680743455887,
0.018178272992372513,
0.029491739347577095,
0.05658041313290596,
-0.00022911479754839092,
0.024493591859936714,
... |
<p>I applied some data to find the best variables solution of regression model using ridge regression in R. I have used <code>lm.ridge</code> and <code>glmnet</code> (when <code>alpha=0</code>), but the results are very different especially when <code>lambda=0</code>. It suppose that both parameter estimators have the ... | g62644 | [
0.09274303168058395,
-0.10168380290269852,
-0.011414638720452785,
-0.024780001491308212,
0.1089712530374527,
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-0.01980111189186573,
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0.027211518958210945,
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0.05... |
<p>I was taught that when we feed our data to machine learning algorithm (e.g. SVM), we should first normalize our data.</p>
<p>Suppose I have a set of data $X = \{x_1,x_2,...,x_n\}$, I knew two-way of normalizing them, let $\hat{\mu}$ and $\hat{\sigma}^2$ be the sample mean and sample variance of X. I can normalize e... | g19806 | [
0.0604722797870636,
-0.06195473670959473,
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-0.013681118376553059,
0.012524823658168316,
0.03305155783891678,
0.04637359827756882,
0.0249762... |
<p>Two large beach holiday destinations near Bangkok, Thailand are Pattaya and Hua Hin. In a random sample of 100 individuals in Bangkok who have been on a weekend away to nearby beach destinations 6 preferred Pattaya and 3 preferred Hua Hin. The other 91 did not have a preference. These individuals were then exposed ... | g62645 | [
0.012009995989501476,
0.029544392600655556,
0.006639930419623852,
0.003350730985403061,
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0.0312... |
<p>I'm analyzing the effect of precision error in optics experiments. One of the relevant quantities is a sum of $N$ complex numbers, each with a complex relative standard error $\epsilon$. How can I calculate the standard error of the summation? </p>
<p>I've been thinking along the lines of a Gaussian random walk bu... | g62646 | [
-0.032832495868206024,
-0.03145837411284447,
-0.012008572928607464,
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0.025608772411942482,
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0.09953049570322037,
0.0... |
<p><strong>Background</strong></p>
<p>I have a large dataset that contains three binary outcomes for individuals belonging to groups. I am interested in jointly modeling these binary outcomes because I have reason to believe they are positively correlated with one another. Most of my data is at the individual level, h... | g62647 | [
-0.05273575708270073,
-0.025613747537136078,
-0.008312582969665527,
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... |
<p>Consider the scenario of making successive predictions about the outcome of a sporting event while it is taking place. I will use tennis as a concrete example because it has clearly defined moments at which it is sensible to make a new prediction (i.e. after every point is played) but I am also interested in cases s... | g19811 | [
0.02510560117661953,
-0.008937017992138863,
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<p>I don't understand the explanation in <code>R</code>'s help file for <a href="http://stat.ethz.ch/R-manual/R-patched/library/stats/html/effects.html" rel="nofollow">effects()</a>: </p>
<blockquote>
<p>For a linear model fitted by <code>lm</code> or <code>aov</code>, the effects are the uncorrelated single-degree... | g19812 | [
0.04000353440642357,
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0.001679261913523078,
0.05027391389012337,
-0.0039... |
<p>I working with a dataset of around 4000 variables. I decided to carry out a PCA analysis for the data, but I am not quite sure about the suitable number of variables I should include in the test.
Would feeding a big number (such as 4000) variables interfere with the PCA accuracy? As far as I can understand from the... | g62648 | [
0.027849476784467697,
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0.040618181228637695,
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... |
<p>I have estimated the following model on Stata 13:</p>
<p><code>tobit y x1 x2 x1x2</code></p>
<p>where:</p>
<ul>
<li>$y$ is aid spending by a charity in a developing country</li>
<li>$x_1$ is GDP per capita of developing country</li>
<li>$x_2$ is proportion of official funding that charity receives (so is a fracti... | g19813 | [
0.018431097269058228,
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<p>My teacher likes to give online quizzes that are about 20-30 questions long. Every student has the same questions in the same order. We are not told after taking the quiz which questions we got wrong, but the system does tell us our score.</p>
<p>That made me curious as to inferring the answers statistically. (Note... | g62649 | [
0.03942091017961502,
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0.013... |
<p>If the density $f(x,y) = c$ when $x>0$, $y>0$, $x+y < 1$ and $0$ otherwise, find $$E((X+Y)^2 | X = x)\text{ for } x \in (0,1).$$</p>
<p>How to approach this question?</p>
<p>Can we approach it by letting it equal to </p>
<p>$$E( (X+Y)^2 | X = x) = E (E( (X+Y)^2 | X = x))$$</p>
<p>Just not sure...</p> | g62650 | [
0.04645153880119324,
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0.08224767446517944,
0.04... |
<blockquote>
<p>Let $X_1,X_2, \dots,X_n$ be a sample from a population with distribution function $F(x-\theta)$, where $F$ is symmetric around $0$. The $\alpha$ trimmed mean $T_n(\alpha)=\dfrac{1}{n-2\lfloor n\alpha \rfloor }\displaystyle\sum_{i=\lfloor n \alpha \rfloor+1}^{n-\lfloor n \alpha\rfloor}X_{(i)}$ is asymp... | g62651 | [
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0.... |
<p>I am trying to implement an xorshift* PRNG (practically an xorshift with a multiplication step in the end) as a long term replacement of Java's Math.Random. I have been reading an article pointed out <a href="http://stats.stackexchange.com/a/83557/3014">in an answer to another question</a>, but I am confused with th... | g62652 | [
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0.00... |
<p>Let $Y$ denote the median and let $\bar{X}$ denote the mean, of a random sample of size $n=2k+1$ from a distribution that is $N(\mu,\sigma^2)$. How can I compute $E(Y|\bar{X}=\bar{x})$?</p>
<p>Intuitively, because of the normality assumption, it makes sense to claim that $E(Y|\bar{X}=\bar{x})=\bar{x}$ and indeed th... | g62653 | [
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0.0226250514388084... |
<p>I am sorry if my question is not fit here. If so, please recommend me the correct forum.
I am thinking of estimating a fuzzy model using the EM method. I have a set of observations from a nonlinear model. I would like to Takagi-Sugeno fuzzy regression model, where the parameter estimation of the consequent parts are... | g19816 | [
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0.0... |
<p>It was my understanding that the training data has to be labeled to create a model and then label any unseen data. As in the case of using ANN, how is Google able to identify <a href="http://googleblog.blogspot.co.uk/2012/06/using-large-scale-brain-simulations-for.html" rel="nofollow">cats</a> in Youtube videos with... | g62654 | [
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0.03... |
<p>I have two tables, you can think of them of results of two models. I would like to compare them to a benchmark to evaluate which model is a better fit. What statistical technique do I need to do this ?</p>
<p>Right now, I'm just summing the absolute differences, with the smallest being the best fit, this doesn't se... | g19817 | [
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<p>My objective is to improve out of sample generalization of my random forest <em>while holding the number of trees constant</em>. </p>
<p>Suppose that I am only allowed to use $n$ trees on the out of sample data but it is computationally feasible to estimate $z$ trees on my in sample data where $z \geq n$ (from whic... | g19818 | [
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... |
<p><strong>Context:</strong> Consider a $M/E_2/1$ queueing system, where the customer arrival rate is $\lambda$ and the service time distribution has a gamma distribution with parameters $2$ and $\mu$, i.e. with p.d.f. $\mu^2te^{-\mu t}$ , $t ≥ 0$</p>
<p><strong>Question:</strong> Assuming that the system is in equili... | g606 | [
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0.015... |
<p>I have the following situation:</p>
<ul>
<li>I'm asking SMEs (small & medium enterprises) how they have reacted to situation ABC.</li>
<li>Because I don't know who has encountered situation ABC, I ask all SMEs of one country (X).</li>
<li>Only Y percent respond, because the others hadn't encountered this situat... | g62655 | [
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0.03... |
<p>If random points are chosen from a circle, what is the probability that all of them come from same semicircle ?</p>
<p>My reasoning is that;
Let two random points be chosen first. Obviously then both of them lie in same semicircle. Now mark any diameter including those two on the same side of it. Any more point c... | g10145 | [
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<p>My question is specific to transportation modelling using a nested logit (NL) model.
I wonder how to make a program including a <em>t</em>-parameter, <em>t</em>-value, and likelihood in R.
I did estimation in a multinomial logit (MNL) model, and now I am planning to advance it using NL. Can anybody help do this?</... | g19819 | [
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<p>My name is Abhi and I am fairly new to statistics. I found some sample exercises online & I am trying to solve them to get a better understanding of model development. </p>
<h3>Problem Statement</h3>
<p>Assume a forum like stack exchange or cross validated. Using parameters like number of comments, number of u... | g19821 | [
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<p>I am interested in estimating an adjusted risk ratio, analogous to how one estimates an adjusted odds ratio using logistic regression. Some literature (e.g., <a href="http://aje.oxfordjournals.org/content/159/7/702.abstract" rel="nofollow">this</a>) indicates that using Poisson regression with Huber-White standard e... | g62656 | [
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0.03643286973237991,
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-0.00494418945163488... |
<p>X is a real-valued random variable with characteristic function:</p>
<p>$\hspace{20mm}$$\phi(t) = \frac{1}{2}[cos(t) + cos(t\pi)$, $\hspace{10mm}-\infty<t<\infty$.</p>
<ol>
<li><p>Is the distribution of X completely continuous?</p></li>
<li><p>Is there an r such that $E(X^r)$ does not exist or is infinite?</... | g19822 | [
0.0475170761346817,
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0.0023077805526554585,
0.016440637409687042,
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0.009977017529308796,
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-0.022111359983682632,
... |
<p>I have time series data of many variables (This data comes from high throughput biological experiments, which measure the amount of particular biological components such as RNA content of a cell etc., )</p>
<p>The time series looks like </p>
<p>$x \to x_1, x_2, x_3 $ which is the value of $x$ at time points $1,2,3... | g62657 | [
0.006294798105955124,
0.035468973219394684,
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0.0950557217001915,
0.03134073317050934,
0.0... |
<p>I'm not really familiar with Weka, I learned to use it by watching some tutorials so I am not 100% sure if my approach is the correct one.</p>
<p>I have collected the Reuters21758 dataset and I use the documents prescribed in the ModApte split. To make it easy I load training and test instances in Weka (first all t... | g19825 | [
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<p>I was thinking about detecting the veracity of user ratings by examining the time-stamp. Basically I have a series of times $(t_1, t_2, \ldots, t_n)$. So assuming that ratings should normally come in at a constant rate, is there a good way to detect whether some time-stamps are unusually clumped up, because a set of... | g10147 | [
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<p>I want to generate correlated random variables with a given correlation matrix, means, and variances. Does the Cholesky decomposition only work when the initial random variables are iids with the same mean and variance?</p> | g16224 | [
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... |
<p>I have measured 23 patients three times pre and three times post treatment. Now I would like to see if the treatment had a significant effect. I thought about using a Wilcoxon rank sum test for this (because I don't know how the characteristic is distributed in the population), which takes two vectors of variables, ... | g62658 | [
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0.011562187224626541,
-0.03214253857731819,
-0.003727829782292247,
-0.06202072277665138,
0.052825234830379486,
-0.009247471578419209,
... |
<p>Sorry for my bad English, could you suggest R-code for the implementation of difference-in-difference regression? I don't understand how many coefficients I need.
In my analysis I compare the effect of a new law on the stock exchange volume, I have 2 periods and 2 samples.
Thanks a lot!</p>
<p>Thanks Jeremy, but i... | g62659 | [
-0.03364897891879082,
-0.022470563650131226,
0.0036816149950027466,
-0.0018144656205549836,
0.012384718284010887,
-0.02896275743842125,
0.07191626727581024,
-0.029951220378279686,
-0.027619173750281334,
-0.003956147003918886,
-0.0707419216632843,
0.05354389175772667,
-0.0009388172184117138,
... |
<p>It is quite common to discuss what metrics to be used for a model/algorithm/method. But when it comes to metrics of datasets, it is much less discussed.</p>
<p>I wonder, what are the general metrics for datasets? That is to say, how does one quantitively measure if a dataset is good or not for its purpose?</p>
<p>... | g200 | [
-0.023089872673153877,
0.013252103701233864,
-0.026157516986131668,
-0.06061793491244316,
0.0011013096664100885,
-0.0016751117072999477,
-0.00009847524779615924,
0.046626392751932144,
-0.04529809579253197,
0.008777099661529064,
0.05601726472377777,
0.004191573243588209,
0.06475894153118134,
... |
<p>What does it mean "The means are statistically equals?" I ask this question because I'm studing ANOVA (<code>anova()</code> function in R) and I know that this test checks if the means of N groups are statistically equals.</p>
<p>My doubt concerns what "statistically equals" means because if I have two series like:... | g42407 | [
-0.012803780846297741,
-0.0021017349790781736,
0.014584355056285858,
-0.001999812200665474,
0.004319153726100922,
0.020669138059020042,
0.02090132050216198,
0.018460135906934738,
-0.014206133782863617,
-0.009304854087531567,
-0.083567775785923,
0.05516621470451355,
0.0024969829246401787,
0... |
<p>We have recently conducted a cluster analysis for an open card sorting task in which 19 experts grouped 112 items each. We achieved decent silhouette values for the cluster analysis but have been asked by reviewers to provide evidence that the number of experts we used was sufficient for this task (I think they are ... | g19830 | [
-0.06814859062433243,
0.04534460976719856,
0.03035528026521206,
-0.04718700051307678,
0.002765636658295989,
-0.057327352464199066,
-0.010003184899687767,
0.021808931604027748,
-0.039472974836826324,
0.027649812400341034,
0.05300161615014076,
-0.04354067146778107,
0.0457356832921505,
0.0112... |
<p>I'm currently building a chart with Excel out of a fair number of lines of statistics.</p>
<p>Since there are too many lines, i cannot plot them all, otherwise the chart would become unreadable.</p>
<p>I'm currently selecting the lines and values by hand, which is a tedious process. I'm trying to automate some of ... | g19831 | [
0.031128885224461555,
-0.009072311222553253,
-0.008449507877230644,
-0.007977455854415894,
-0.02027752995491028,
-0.04145176708698273,
0.010588685981929302,
-0.028411611914634705,
-0.05817196145653725,
-0.06162036955356598,
-0.003087118500843644,
-0.013629214838147163,
0.05971711874008179,
... |
<p>What is the most appropriate sampling method to evaluate the performance of a classifier on a particular data set and compare it with other classifiers? Cross-validation seems to be standard practice, but I've read that methods such as .632 bootstrap are a better choice. </p>
<p>As a follow-up: Does the choice of ... | g19833 | [
0.03531615808606148,
-0.013455795124173164,
0.03182647377252579,
-0.07210475206375122,
-0.0031653151381760836,
0.004341765306890011,
0.0241305660456419,
-0.015253016725182533,
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0.014792263507843018,
0.07246417552232742,
0.033992405980825424,
0.06805621832609177,
0.008... |
<p>For reasons I won't go into, I want to test for group differences between an entire sample A ($n=65$) and a subsample B ($n=45$). All of the variables I want use for mean comparisons are continuous. </p>
<p>Is there an appropriate test for this? </p>
<p>This doesn't seem to meet the sample independence conditio... | g62660 | [
-0.010712887160480022,
-0.035927608609199524,
0.008499016053974628,
-0.03203243762254715,
-0.06485659629106522,
-0.028677888214588165,
0.017295433208346367,
0.027784716337919235,
-0.054386746138334274,
0.016564862802624702,
0.048090338706970215,
0.0032732586842030287,
-0.0811714306473732,
... |
<p>Alright, so I have about a thousand datapoints that I'm plotting on a chart (scatter plot).</p>
<p>Here's a few of the records:</p>
<pre><code>x y
2.426032708 10
9.449923509 24
4.409997771 24
-3.125392294 11
13.04820475 26
</code></pre>
<p>When looking at the full data on a chart, I can visu... | g19834 | [
0.014318966306746006,
0.023028526455163956,
-0.023507224395871162,
-0.02711920253932476,
-0.023355524986982346,
-0.06493079662322998,
0.030038299039006233,
-0.007098337169736624,
-0.034533314406871796,
-0.054231442511081696,
-0.020460933446884155,
0.09206076711416245,
0.07149919867515564,
... |
<p>I am asking this because I know there are IA's for cross sectional estimators and D-in-D estimators, but am unsure if there are any for IV estimation. Does anyone know if there is or isn't, and if there is - what would it be?</p> | g19835 | [
-0.01236278098076582,
-0.04633435606956482,
0.021292669698596,
-0.020101439207792282,
-0.0507533885538578,
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0.018260125070810318,
0.0038550777826458216,
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0.022007744759321213,
-0.02069031074643135,
0.013684486038982868,
-0.015548388473689556,
-0.0... |
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