question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>The settings: we have a sequence of numbers generated from a normal distribution with $\mu=1;\sigma^2 = 1 $. And with every new observation collected, we'd like to test for: $H_0:\mu_0=0$ (two-sided).</p>
<p>From what I've learned in school, there is the Wald's group sequential for when comparing two simple hypoth... | 70,337 |
<p>These are actual reported costs (60) for a series of projects for two years, say USD (though actually not) totalling $57,975,403.24:</p>
<pre><code>(274,680.90) 3,900.13 103,999.61 512,918.71 1,079,734.06
(97,570.45) 4,218.45 110,499.74 516,501.94 1,249,999.48
(43,261.81) 9,951.36 116,287.... | 70,338 |
<p>I have a data set with 7 predictor variables and one dependent variable. The dependent variable has 4 categories so it's not binomial. I need to fit a probit model. I need codes for probit model in R, SPSS or Matlab.</p> | 36,400 |
<p>I wanted to see if the different kinds of supports to small enterprises have contributed to the development/growth of small enterprises using 15 years period data (6 years before implementing these programs & 9 years after it). I used comparative research design & applied linear time series regression. At 1... | 70,339 |
<p>I have a data set on hands with 5,220 cases and I'd like to automate some procedures (but I have almost no programming knowledge). The data has some continuous variables that are grouped by 2 others: the name of species and the locality where they were collected. So, the samples are defined as 'each species on each ... | 70,340 |
<p>As the title suggest...I have a very basic question.</p>
<p>I have a case with the following data:</p>
<pre><code>Universe: 18840 balls total
red balls in the universe: 6680
Sample: 382 balls total
red balls in the sample: 160
</code></pre>
<p>I would like to estimate if the percentage of red balls in my sample i... | 48,472 |
<p>I applied a survey consisting of 12 questions to 120 people and each questions include 4 nominal categories; I want to make comparison of people's answers according to their socio-demographic characteristics such as their educational level or socioeconomic status. All of my comparison criteria consist of nominal cat... | 31,254 |
<p>I'm working for object detection(computer vision) and have some problems in SVM training.
My training configuration is as below.</p>
<ul>
<li>Balanced training set (positive 3998/ negative 3998)</li>
<li>The dimension of my feature set is 2592</li>
<li>Training using LIBSVM with default options, except kernel funct... | 36,401 |
<p><em>The essence of my question is this:</em></p>
<blockquote>
<p>Let $Y \in \mathbb{R}^n$ be a multivariate normal random variable with mean $\mu$ and covariance matrix $\Sigma$. Let $Z := \log(Y)$, i.e. $Z_i = \log(Y_i), i \in \{1,\ldots,n\}$. How do I compare the AIC of a model fit to observed realizations of $... | 70,341 |
<p>I have several files, each of which contains unique terms which are related to each other(without sentence structure). So for finding the word relationships I created a dictionary of bi-grams for every two words occurring in the document, and for every match found I increment the count for the bi-gram occurrence mak... | 29,539 |
<p>What are the advantages of log linear representation in opposite of table representation? Is it simply computational issue ( avoid overflowing)? </p>
<p>For example, in a markov network A-B we can represent the factor P(A,B) as a table:</p>
<pre><code>A B P(A,B)
0 0 10
0 1 1
1 0 1
1 1 10
</code></pre>
<p>Alte... | 70,342 |
<p>I have a set of time series for a given quantity (e.g. CPU). The measurements are roughly evenly spaced, but the data points aren't synchronised between sets and some sets have missing measurements. The measurements often exhibit a strong pattern over the course of an hour or day. </p>
<p>I'd like to compare the mo... | 70,343 |
<p>I am trying to plot the probability mass function of a sample of a discrete metric. </p>
<p>If it was continuous, I know that using pandas it would be as simple as calling:</p>
<pre><code>sample.plot(kind="density")
</code></pre>
<p>But I'm afraid that this is not enough (or not right) for my sample. Is there a f... | 70,344 |
<p>I have an existing fitted logit regression model.</p>
<p>Model:</p>
<p>$\hat{p}(x)=\frac{1}{1+e^{-\hat{\beta}x}}$</p>
<p>With parameter estimates $\hat{\beta}$, and observation $x$</p>
<p>Given a new set of datapoints $x_1,\ldots,x_n$ and $o_1,\ldots,o_n$, I want to construct a confidence interval for $E=\sum_i ... | 70,345 |
<p>I need to conduct cross validation of my data to check for predictive validity. This is what I did so far. I divided the sample into two sub-samples(50-50). In SPSS, I then used the split variable to instruct SPSS to keep the data divided into two-sub samples while running regression. Post this I got two regressio... | 31,260 |
<p>I'm trying to analyze a dataset that originates from sensors located near players' shoes in a match (<a href="http://www.orgs.ttu.edu/debs2013/index.php?goto=cfchallengedetails">http://www.orgs.ttu.edu/debs2013/index.php?goto=cfchallengedetails</a>).</p>
<p>I decided to look at clustering to identify:</p>
<ol>
<li... | 70,346 |
<p>I am testing my hypotheses with a 2x2x2 between subjects design.
Thus I am testing the moderation effects on the dependent variable.</p>
<p>When I used regression to conduct this test, $H_1$ was accepted.
However when I used One- way- ANOVA to further test this, $H_1$ was rejected.</p>
<p>I am just wondering wheth... | 70,347 |
<p>I am conducting an empirical study (relation between earnings and returns).</p>
<p>I have an unbalanced panel with $N=449$ firms and $T=36$ time periods.
Regarding the estimation methods I am confused:</p>
<ol>
<li>In most of the papers they account for firm clustering and time issues and therefore cluster for fir... | 31,261 |
<p>I have estimated a Partial Credit Model in Stata following Zheng, X. and Rabe-Hesketh, S. (2007) "Estimating parameters of dichotomous and ordinal item response models using gllamm".</p>
<p>I'd like to compute Item Information Curves but I can't figure out how to do it from what I found in Google or in other StackE... | 31,263 |
<p>In short: suppose I have observations for times taken to do some action. I want to estimate, how long will it take to complete a sequence of actions. The estimate should minimize the mean absolute error (L1 norm). </p>
<p>=== </p>
<p>Details:
I have observations for positive, non-identically distributed RV $x_i$, ... | 31,265 |
<p>I'm getting more experience in building predictive models like trees and random forests, but most of my experience is using data that is basically single observations (rows) with many variables (columns). How do I deal with making predictions about things that could potentially have a variable number of objects insi... | 70,348 |
<p>The journal <em>Applied Statistics</em> used to have a section on algorithms, which are available <a href="http://lib.stat.cmu.edu/apstat/" rel="nofollow">online</a>. Griffiths and Hill also published a selection of these algorithms in a <a href="http://amzn.com/0470201843" rel="nofollow">book</a> in 1985. But I can... | 70,349 |
<p>I realize this might be a too general question, so I'll describe what I'm doing right now first. </p>
<p>I'm working for a virtual insurance company and I have this dataset. It has severity (meaning payment/number of claims), type of car, gender, marital status, age of car, risk type (high and low), company name (o... | 70,350 |
<p>(Model1)
. reg lnQ lnL lnK COOP</p>
<pre><code>------------------------------------------------------------------------------
lnQ | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
lnL | .7682515... | 70,351 |
<p>Is the <a href="http://en.wikipedia.org/wiki/Theil%E2%80%93Sen_estimator" rel="nofollow">theil-sen estimation</a> in robust regression only limited to a two dimensional problem or can you use it for more than one indepedent variable as well?</p> | 70,352 |
<p>I have run a split splot model in SPSS (via repeated measures function) and I would like to reproduce my results using R. To do so I used ezANOVA function from ez package to obtain sphericity tests and correction and type III SS. I have read that aov function does not give type III SS. So far the results are identic... | 70,353 |
<p>Good day,</p>
<p>I will am currently doing some self-study on Simple Linear Regression. I understand the formula:</p>
<p>$$\hat{Y}_i=\beta_0+\beta_1 X_i$$</p>
<p>But what does it mean when the value of $\beta_1$ is 0? Does it mean that $X$ and $Y$ have no relationship?</p>
<p>Appreciate some advice and explanati... | 70,354 |
<p>I would have thought that the degrees of freedom would be the same as a regular t-test, i.e. N - 1, since in a contrast we are either comparing two groups, or two sets of groups. Why do we instead use the within SS degrees of freedom (N - k)?</p>
<p>Here are some example SPSS tables from <a href="http://wiki.uva.nl... | 31,268 |
<p>Forgive me if this question is answered elsewhere - it may be all I need to be told is the correct terminology.</p>
<p>I have a survey in which I ask a number of Yes/No questions (actually Yes/No/Don't know - but for simplicity I want to assume Yes/No for now).</p>
<p>Say for one question I have 583 say yes and 2... | 31,269 |
<p>I have downloaded the sample codes from kaggle for the randomForest benchmark <em>[URL?]</em> and there's this part that I don't understand.</p>
<pre><code> appendNAs <- function(dataset, cols) {
append_these = data.frame( is.na(dataset[, cols] ))
names(append_these) = paste(names(append_these), "NA", sep =... | 70,355 |
<p>i have done some research about spatial patterns analysis, using some spatial statistics mesures, all the cours that i found talks about spatial statistic in the context of GIS,
in the context of image analysis, i am trying to use different technics such as Quadrat Analysis, Nearest Neighbors , Joins Count, Moran's... | 36,883 |
<p>Can i apply a standar OLS ECM after proving cointegration using johansen approch? The results for VECM are uncertain and one of the equation gives a negative R squared.</p>
<p>If i want to test only one dependent variable in a simple bivariate model.</p> | 70,356 |
<p>I need to utilize two different classifier to get best classification results. Since, it seems that they complement each other (not sure I am not expert btw). ROC characteristics are given below (testing scheme is 10-fold cross validation):</p>
<p><strong>MetaCost [0 8; 1 0] Alternating Decision Tree (ADTree)</stro... | 70,357 |
<p>I have been assigned the following question</p>
<p>"On the basis of the Bank of England's 2013 survey of the Financial position of
British households, given in the data file [households], examine the statistical
and econometric relationships <strong>between household debt-to-income ratios and the
respondents backgr... | 70,358 |
<p>my question is "What is command used to generate ROC PLOT in libsvm as well as for specificity , sensitivity and precision what is the command in libsvm " i Am using ubuntu</p> | 70,359 |
<p>I have dendrogram and a distance matrix. I wish to compute a heatmap -- without re-doing the distance matrix and clustering.</p>
<p>Is there a function in R that permits this?</p> | 36,408 |
<p>What is the probability of absorption at $ 0 $, as a function of position $ x $, for a 1D random walk (on $ \mathbb{Z} $) with asymmetric step sizes?</p>
<p>For example, suppose that you can take two steps to the right with probability $ p $, or one step to the left with probability $ q=1-p $. I calculated the prob... | 70,360 |
<p>I've seen this comment made in various textbooks and papers. For example, the online textbook by Rob J Hyndman and George Athanasopoulos states at <a href="http://otexts.com/fpp/2/5/" rel="nofollow">http://otexts.com/fpp/2/5/</a> that</p>
<blockquote>
<p>Another problem with percentage errors that is often ove... | 70,361 |
<p>It is known that the bootstrap can fail.</p>
<p>I read in Section 6 of <a href="http://www.jstor.org/stable/2240410">Bickel and Freedman (1981)</a> that the bootstrap fails when you wan to use it to evaluate the MLE for estimating the parameter of a continuous uniform distribution.</p>
<p>I read Secion 7.4 of <a h... | 914 |
<p>I have a set of estimates of function values, along with estimates of their standard errors. To somewhat simplify matters: for $x$ running from $1$ up to $70$ in (integer) steps (in fact a parameter in model selection), I have an estimate of the matching $y$-value (in fact an AUC) and an estimate of its SE. I cannot... | 31,277 |
<ul>
<li>I am new to R(learned the basics)</li>
<li>In my current job I have to solve the following problem(the following is an example) </li>
</ul>
<blockquote>
<ul>
<li>Suppose we have 10, 000 users</li>
<li>For each user we have his expected monthly spending(in dollars)(with some method that I don't know) fo... | 70,362 |
<p>Currently I am investigating interpolation of 3D data with radial basis functions (RBF) and I am wondering that there are quite a few families of such <a href="http://people.maths.ox.ac.uk/~wendland/research/old/reconhtml/node2.html" rel="nofollow">(see table1 here)</a>.</p>
<p>However, I cannot find any discussion... | 31,280 |
<p>I estimate a two-level model, random slopes and random intercepts. The variance of each random term is significant based on Chi-square test, but the covariance (of slopes and intercepts) is not significant. Can I just safely remove the covariance term, thus simplifying the variance function? Are there any substantiv... | 70,363 |
<p>I have this linear model:</p>
<pre><code>fit = glm(Survived ~ Pclass + Sex + Age + SibSp + Parch + Fare,
data=passengers, family=binomial)
summary(fit)
Coefficients:
Estimate Std. Error z value Pr(>|z|)
(Intercept) 5.318162 0.571693 9.302 < 2e-16 ***
Pclass -1.175648 0.1... | 70,364 |
<p>I have a question about something that my statistics teacher said about the following problem:</p>
<hr>
<p>There are two hospitals named Mercy and Hope in your town. You must choose one of these in which to undergo an operation. You decide to base your decision on the success of their surgical teams. Fortunately, ... | 49,700 |
<p>For classifiers with binary outputs, their performance is summarized by a true positive rate and false positive rate. To <a href="http://stats.stackexchange.com/a/21728/2728">interpolate</a> the performance between two classifiers $A$ and $B$ with their respective (true positive rate, false positive rate) being $(t_... | 70,365 |
<p>I'm trying to determine if my dataset of continuous data follows a gamma distribution with parameters shape $=$ 1.7 and rate $=$ 0.000063.</p>
<p>The problem is when I use R to create a Q-Q plot of my dataset $x$ against the theoretical distribution gamma (1.7, 0.000063), I get a plot that shows that the empirical ... | 37,028 |
<p>My question is related to <a href="http://stats.stackexchange.com/questions/15475/how-to-derive-the-variance-of-a-weighted-moving-average">this one</a>. I am calculating averages, actually as many as I have samples because I calculate a running average, and for equal weighting I know how to calculate the $95\%$ CI, ... | 70,366 |
<p>Consider the model below:</p>
<p><img src="http://i.stack.imgur.com/1cs1n.png" alt="enter image description here"></p>
<p>In many research papers, significance of statistical results are indicated by <code>*</code>, <code>**</code>, and <code>***</code> as a significant value at respectively the <code>1%</code>, <... | 48,743 |
<p>I have a 2X2 factorial experiment where I am interested in seeing the effect of two different nutrient solutions (N and W) on the appearance of root tips of two different plant species (A and B). I used 3 plants per species X treatment combination. I took daily counts of the number of root tips of each plant over t... | 70,367 |
<p>I've written a small hierarchical clustering algorithm (for better or for worse). I'd like a quick way of visualizing it, any tooling ideas?</p> | 70,368 |
<p>Suppose I have some sample $X$ drawn from some unknown multivariate distribution $F(A,B)$, and I want to test the null hypothesis that a particular point $x$ was drawn from $F$.</p>
<p>Would it be legitimate to fit the PDF for $F$ using kernel density estimation, then evaluate it at $x$ and take this as my p-value?... | 31,290 |
<p>I am modelling the impacts on students' achievemens using HLM (2 levels only), with the lme4 package in R. I would like now to estimate the Empirical Bayes Estimates and the Empirical Bayes Grand Means for each group of the 2nd level, using R.</p>
<p>Please, would you be able to point me to any source or give me an... | 31,291 |
<p>I wonder if there is a simple way to produce a list of variables using a for loop, and give its value.</p>
<pre><code>for(i in 1:3)
{
noquote(paste("a",i,sep=""))=i
}
</code></pre>
<p>In the above code, I try to create <code>a1</code>, <code>a2</code>, <code>a3</code>, which assign to the values of 1, 2, 3. Howe... | 37,713 |
<p>The <a href="http://en.wikipedia.org/wiki/Akaike_information_criterion" rel="nofollow">Wikipedia article for AIC</a> says the following (emphasis added):</p>
<blockquote>
<p>As an example, suppose that there were three models in the candidate set, <strong>with AIC values 100, 102, and 110.</strong> Then the secon... | 70,369 |
<p>I have a couple of questions about regARIMA models:</p>
<ol>
<li><p>What is the underlying principle of the R function <code>auto.arima</code> when xreg is different from NULL? Does it first perform a regression of the time series on the explanatory variables and then select the best ARIMA model for the residuals o... | 70,370 |
<p>I have a series of non-negative integers $y=(y_1,y_2,..., y_n)$ and a design matrix $y = \beta_0 + \beta_1 x_1 + \beta_2 x_2 + \beta_3 x_1 x_2$, where $x_0$ and $x_1$ are $0$ or $1$, $x_1x_2$ is the interaction, and $\beta_0 \ldots \beta_3$ are parameters we want to estimate. For example, the data look like</p>
<pr... | 41,813 |
<p>I am exploring a tree structured as follows:</p>
<p>A/ parent node = parent population, size N, with a proportion of success for an experiment (eg. p = nb success / N)</p>
<p>B/ child nodes = sub populations for a give parent node. Ex.: level one child sizes are n1, n2, ... nn, where n1 + n2 + ... + nn = N. Succes... | 70,371 |
<h3>Story (spoilers!)</h3>
<p>The puzzle:</p>
<blockquote>
<p>Chuck-a-Luck is a gambling game often played at carnivals and gambling
houses. A player may bet on any one of the numbers 1,2,3,4,5,6. Three
dice are rolled. If the player's number appears on one, two, or three
of the dice, he receives respective... | 70,372 |
<p>Suppose that the number of accidents occurring at a particular intersection each week is a Poisson random variable. It is estimated that the probability of having at least one accident in a week, at the intersection, is 0.98. </p>
<p>Calculate the average number of accidents occurring each week at the intersection.... | 70,373 |
<p>A one-period jump diffusion model of a stock is the following: given the stock value at $T0$, $S(T0)$, the stock value at time $T$, $S(T) = S(T0)exp(x)exp(y)$. Given the inputs $m$, $s$, $pup$, $pdown$ and $\lambda$, and:</p>
<ol>
<li>x is normally distributed with mean m and standard deviation s</li>
<li>y equals ... | 70,374 |
<p>I am using the following code for grid search on libsvm:</p>
<pre><code>bestcv = 0;
for log2c = -1:3,
for log2g = -4:1,
cmd = ['-v 5 -c ', num2str(2^log2c), ' -g ', num2str(2^log2g)];
cv = svmtrain(heart_scale_label, heart_scale_inst, cmd);
if (cv >= bestcv),
bestcv = cv; bestc = 2^log2c; bestg = 2... | 70,375 |
<p>In software development, we often write unit tests to ensure that a particular portion of the code is working as expected. For example, consider the problem of drawing a color at random from Colors=(Red, Green, Blue). Suppose, that we write a function:</p>
<pre><code>drawn_color = draw_color(Colors)
</code></pre>
... | 70,376 |
<p>I think I've developed a systematic quantile normalization technique. I did this with music but I think it can also be done with light and other frequency based information.</p>
<p>The algorithm is as follows:</p>
<p>Given a series of frequency data:</p>
<blockquote>
<ol>
<li><p>Systematically move it to a kn... | 70,377 |
<p>My main field is machine learning and 90 % of what I do is to try to improve the prediction error. </p>
<p>Recently I have started to work with a medical group. They are mainly doctors so I do not know how much I can trust their statistical knowledge. </p>
<p>What they commonly do is to fit logistic regression and... | 70,378 |
<p>I am a medical scientist doing observer agreement analysis on some very simple data using Cohen's Kappa. I have 2 observers. They score a bunch of scans on a 3 point scale for a pattern called honeycombing (definitely present, possibly present, absent). They also score for emphysema on the same 3 point scale. It is ... | 70,379 |
<p>I've run a 2 (treatment and no treatment) x 2 testing occasions (pre and post) Repeated Measures ANOVA. In addition, I entered several tests given at both time points, so under the Repeated Measures Define Factor(s) window option for Measure Name, I've entered 5 different tests used. </p>
<p>In the output, I am try... | 70,380 |
<p>In psychology and other fields a form of stepwise regression is often employed that involves the following: </p>
<ol>
<li>Look at remaining predictors (there are none in the model at first) and identify the predictor that results in the largest r-square change; </li>
<li>If the p-value of the r-square change is les... | 216 |
<p>I want your advice regarding data I have, that comes from the Ophthalmic world. I have a small sample of 12 people (in future studies will be larger, this is a small pilot).</p>
<p>Each person received a medicine to lower his intraocular pressure, which is a metric scale measure (continuous). In this small study, p... | 70,381 |
<p>Consider the ARMA(2,1) time series
$$
x_t−0.1x_{t−1}−0.06x_{t−2}=w_t−0.5w_{t−1} ,
$$
where $w_t$ is white noise with mean zero and variance $\sigma^2_w$.
Find the expectation of
$$
(x_t−0.1x_{t−1}−0.06x_{t−2})x_{t−h}, \quad h=0,1,...
$$
and
$$
(w_t−0.5w_{t−1})x_{t−h}, \quad h=0,1,...
$$
and show how this can be used... | 70,382 |
<p><strong>The situation</strong></p>
<p>I have a dataset with one dependent $y$ and one independent variable $x$. I want to fit a continuous piecewise linear regression with $k$ known/fixed breakpoints occurring at $(a_{1}, a_{2}, \ldots, a_{k})$. The breakpoins are known without uncertainty, so I don't want to estim... | 70,383 |
<p>I am running an experiment (it's an image processing experiment) in which I have a set of paper samples, and each sample has a set of lines. For each line in the paper sample, its strength is calculated, which is denoted by say '<strong>s</strong>'. For a given paper sample I have to find the variation amongst the s... | 916 |
<p>I'm looking at the difference in demographics of people with a disease pre-outbreak and post-outbreak (e.g. age, sex, location etc).</p>
<p>I know how to use $t$ tests and $\chi^{2}$-tests for comparison (e.g. difference of means for age), and I'm getting ridiculous statistical significance, but what I would like t... | 70,384 |
<p>Does the plotted data look like a garch model?
If it does, with which test, I can support this claim</p>
<p><img src="http://i.stack.imgur.com/gEHr3.png" alt="http://i.stack.imgur.com/gEHr3.png"></p>
<pre><code>[1] 0.187415738 0.477868164 0.295777631 0.575167970 0.469157108
[6] 0.328171826 1.292894... | 70,385 |
<p>I'd like to cluster points based on a distance criteria. As
I want to cluster spatial points I am using euclidean distance
and a hierachical cluster approach. In a final step I'd like to
cut the dendrogramm at a specific distance to make sure that all
cluster means are spatially separated by a minimum distance sp... | 70,386 |
<p>Im not understanding the following;</p>
<p>suppose $y \sim N (\mu,\sigma^2)$
and we have a prior $\mu \sim N (\mu_0, \sigma^2_1)$</p>
<p>Then we can figure out the posterior distribution.</p>
<p>What i dont understand is suppose</p>
<p>$y=\mu+e$ where $e \sim N(0,\sigma^2_e)$
how do I know that $y \sim N (\mu,... | 70,387 |
<p>short intro:
I wish to explain seedling abundance in a savanna ecosystem with two factors. one factor is 'canopy' which is either 0 (under a tree) or 1 (not under a tree). the other factor is distance from forest edge for which i have 5 different distances. I also have three covariates :'tree density' (which was mea... | 70,388 |
<p>Id like to run a non parametric test such as the Friedman test on a dependent variable of my 8 subjects who have done a task under four different conditions.</p>
<p>I only found examples of how to input the data which had one value per condition for each subject: four vectors of 8 values (one for each subject) for ... | 31,316 |
<p>I am measuring the frequency of consonants in a sample lexicon of a language.
The results are as follows:</p>
<pre><code>+-----+-----+-----+-----+----+----+-------+
| p | t | k | m | n | r | Total |
+-----+-----+-----+-----+----+----+-------+
| 278 | 256 | 122 | 189 | 83 | 72 | 1000 |
+-----+-----+-----+... | 70,389 |
<p>From the documentation for <code>anova()</code>: </p>
<blockquote>
<p>When given a sequence of objects, ‘anova’ tests the models against one another in the order specified...</p>
</blockquote>
<p>What does it mean to test the models against one another? And why does the order matter?</p>
<p>Here is an example f... | 31,318 |
<p>If I take some sequences of random numbers generated by a random number generator with uniform distribution, will the resulting sequences be uniformly distributed as well?</p>
<p>By example, if I have a generator that returns 1, 2, or 3, what are the probabilities to get [1, 1, 1] and [1, 2, 3]?</p> | 70,390 |
<p>Recently I have taken up one assignment wherein I am mesuring the competitiveness of indian apparel export firm. To compute competitiveness I used a survey where firm owners were given 12 questions to rate their competency from 1 to 10. After response collection, I did a Factor Analysis (PCA) which gave me three fac... | 70,391 |
<p>At every step $k$, a Markov chain Monte Carlo algorithm for Bayesian inference with Gibbs sampling draws a parameter of the model to fit, $\beta_i^{(k)}$, from the conditional $Pr\left(\beta_i^{(k)}|\beta_1^{(k)},...,\beta_{i-1}^{(k)},\beta_{i+1}^{(k-1)},...,\beta_N^{(k-1)},X\right)$, where $X$ is the observed data.... | 70,392 |
<p>I have to train a convolutional network. When I visualize its conv filter matrices from a layer, many filters are quite similar, almost equal.</p>
<p>1) Don't you know a common way to detect couples of similar kernels? Maybe, it is somehow connected with their correlation?</p>
<p>2) Don't you know any good strateg... | 31,321 |
<p>Can anyone give me advice on computing the asymptotic confidence intervals for a difference in quantiles of a distribution? For example, I have fit a log-normal distribution to doubly interval censored data with a maximum likelihood estimator and want to make statements about a percentage of the probability mass fa... | 70,393 |
<p>In a multiple linear regression I have one predictor showing a cubic relationship with the outcome. If the same predictor $A$ is also part of an interaction with a continuous variable $B$, do I have to apply the polynomial transformation to both terms?
$$
\hat{Y} = {c} + \beta_1{A} + \beta_2{A^2} + \beta_3{A^3} + \... | 70,394 |
<p>How to show what is going on if we drop significant variable in logit model ? Bias and heteroskedasticity should emerge. But what is the framework for showing such behaviours in econometric models ?</p> | 70,395 |
<p>In my dataset, there's a binary response, some factors, and some covariates. In particular, there are some covariates that are always present when <code>factor1=="A"</code> and these covariates are always missing (<code>NA</code>) when <code>factor1=="B"</code>. This missingness is structural, not random; it doesn't... | 39,257 |
<p>I am estimating a stochastic frontier with a mixed model.
So far the half normal distribution worked good but I need a truncated normal distribution. It does not work, and I receive the error „Expected collection operator c“. I am using R2WinBUGS and as you can see in the model I have tried OpenBUGS and WinBUGS. Any... | 49,848 |
<p>I have two groups of samples, each group of size 8. Each sample comes from an individual $i = 1 \dots 16$ and is a proportion $m_i$ of DNA methylated sites at a specific position in a genome. This can take a value between 0 and 1. We can safely assume that there is no variability between samples if they were taken f... | 70,396 |
<p>I am analyzing a survey data set. One of the items in the survey is: </p>
<pre><code>"I plan to work hard in my statistics course"
1=Strongly Disagree
2=Disagree
3=Neither Disagree or Agree
4=Agree
5=Strongly Agree
</code></pre>
<p>No one selected option 1 of Strongly Disagree. This is to be expected but t... | 41,835 |
<p>I'm relatively new to survival analysis and try to get my data in the right shape.</p>
<p>I have two tables both concerning the observed individuals. If I just would use one of the tables, I would have continuous information on each individual without any overlapping periods.</p>
<p>As I however also need the info... | 31,327 |
<p>I would like to introduce two supplementary variables into a PCA I'm conducting on a set of data measuring concentration in different material phases. </p>
<p>However I'm unclear as to how to interpret the correlation of the "supplementary" variables to the principal component (as opposed to how I would interpret a... | 31,329 |
<p>If I run a <code>randomForest</code> model, I can then make predictions based on the model. Is there a way to get a prediction interval of each of the predictions such that I know how "sure" the model is of its answer. If this is possible is it simply based on the variability of the dependent variable for the whol... | 46,171 |
<p>I was wondering if anyone can explain to me the intuition beyond the Clopper-Pearson CI for proportions.</p>
<p>As far as I know, every CI includes a variance in it. However, for proportions, even if my proportion is 0 or 1 (0% or 100%), the Clopper-Pearson CI can be calculated. I tried looking at the formulas, and... | 21,762 |
<p>I've started reading about Random Forests and one of the attributes that appeals to me is that they are good at dealing with independent variables that interact with one another. Does Random Forest also "automatically" transform variables into, for example, the square of the variable? Is there a good reason to squ... | 31,330 |
<p><strong>Simple case:</strong> Suppose we have $N$ observations of $X_i$ that we believe are theoretically iid binomial random variable $\text{Binomial}(k, p)$. Well, one way we could test to see if this is true is using the standard Pearson's chi-squared statistic.</p>
<p><strong>The question:</strong> Suppose we h... | 70,397 |
<p>Please consider the following OLS model:</p>
<p><img src="http://i.stack.imgur.com/9l9iB.png" alt="enter image description here"></p>
<p>As a rule of thumb, a VIF score of max. 5 is considered acceptable collinearity in most fields. So for the better part I believed this model to be quite nice and significant (R-s... | 70,398 |
<p>For calculating the concentration of an unknown sample, my average value after three trials was about .03425 +- twice the standard deviation (.00159)</p>
<p>In comparing twice the standard deviation to the average value, </p>
<p>is my precision about average?</p> | 48,985 |
<p>If $X_i, i=1,...,$ are independent, identically distributed $\operatorname{N}(0,1)$ random variables, and $Y_i = X_i^2$ are independent $\operatorname{Gamma}(\frac{1}{2},\frac{1}{2})$ RVs, use the Central Limit Theorem to calculate the approximate values of the probabilities:<br><br>
$\sum_{1}^{50} {Y_i \gt 40}$ and... | 31,331 |
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