question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>What is the difference between stratified CV and CV?</p>
<p>Wikipedia says: </p>
<blockquote>
<p>In stratified k-fold cross-validation, the folds are selected so that
the mean response value is approximately equal in all the folds. In
the case of a dichotomous classification, this means that each fold
cont... | g63769 | [
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<p>Suppose you have two null hypothesis for two parameters, $\theta_1$ and $\theta_2$ based on the same variable $X$. So for example, $\theta_1$ is mean of $X$ in group 1, whereas $\theta_2$ is mean of $X$ in group 2.</p>
<p>In reality there may be four true states</p>
<ol>
<li>$\theta_1 \ne 0$ and $\theta_2 \ne 0$</... | g63770 | [
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<p>I have a response variable with 2 categories and $500$ predictor variables. The $500$ coefficient $a_1, a_2, a_3, \ldots, a_{500}$ ranges $(-1, 1)$. Positive $a_i$ indicates category A; negative $a_i$ indicates category B. The larger the coefficient, the stronger it indicates its correspondent category. I get the co... | g63771 | [
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<p>I have 5 categories, each category is divided into the subcategories low, medium and high. An object can belong to one or more of these categories with a number between 1 and 100 in each subcategory but the sum for each category can no exceed 100. Is there are a way to summarise this into one single number?</p>
<p>... | g21605 | [
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<p>I have a dataset with a very simple logfile-like structure, I want to subset the data according to date ranges but can only do on one parameter.</p>
<p>my data looks like this:</p>
<pre><code> date_time loc_id node energy kgco2
1 2009-02-27 00:11:08 87 103 0.00000 0.00000
2 2009-02-27 01:05:05... | g40992 | [
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<p>I am working on a vein pattern recognition project based on SURF algorithm and Euclidean distance. I have completed my program to find the maximum and minimum distance between vein features and find a match exactly when there is an identical image. That is, the max and min distance between two images is zero. In thi... | g63772 | [
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<p>Let $Y_1$ and $Y_2$ be independent r.v.s, and $X$ be another random variable.</p>
<p>What is $E[X|Y_1, Y_2]$? Is $E[X|Y_1, Y_2]$ equivalent to $E[X|Y_1] \cdot E[X|Y_2]$?</p>
<p>More specifically, is there a formula for the density of $f_{X|Y_1,Y_2}$ just like $f_{X|Y_1}$$=$$f_{X,Y_1}/f_{Y_1}$ (assuming that regula... | g21607 | [
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<p>My background is in machine learning and statistics, but I am relatively new to psychometrics and testing. Nearly all of the literature I've found on item reliability refers to Chronbach's alpha or methods that assume all items are administered to all subjects (and what little I've seen for adaptive or IRT models is... | g63773 | [
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<p>I have four databases of books that I have assembled from various sources, websites, etc. I would like to merge the databases, but I face a significant merging issue in that there is no "perfect" match ID among the databases. Each database has the title and publication date, but it's not perfect. For example, I migh... | g21609 | [
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<p>I'm doing some experiments to assess the extend to which MV skewed distributions can affect eigen-vectors (and more specifically Deming regressions). </p>
<p>Suppose $X=(x_i,...,x_n')$ with $x_i \in \mathbb{R}^p$, $1\leq i \leq n$ and for simplicity $p=2$.</p>
<p>I'll be using a (univariate) measure of directiona... | g21610 | [
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<p>I am using the Weka API for my research about document classification. I wish to apply Latent Dirichelet Allocation on my dataset followed by using a classifier in Weka. However, it is not so clear to me how I can perform LDA on my raw textual data and represent it in a way I can feed it to the classifiers in Weka s... | g63774 | [
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<p>For fun and amusement, you wonder how well student grades in Course 101 can predict scores in Course 102. So, you do a regression on grades from both classes. </p>
<p>If you got an r = .59 with $r^2$ = 35%, would you consider this strong or weak? Can you say anything more than concluding, "There’s obviously an a... | g63775 | [
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<p>I am using OLS to estimate the effects of various factors on the sales of different items. The data are monthly, and vary somewhat in the number of monthly observations available (some of the items have only been sold for, say, 18 months while others have data going back for years).</p>
<p>Should I pick some n (e.g... | g63776 | [
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<p>I'm not entirely sure this question belongs here. (Maybe better suited on stackoverflow or theoretical computer science). But here it goes.</p>
<p>I'm reading a paper called. "Time-Frequency Analysis of Heart-Rate Variability". In this paper they discuss a new algorithm to automatically remove artifacts from a sign... | g63777 | [
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<p><a href="http://en.wikipedia.org/wiki/Mutual_information" rel="nofollow">http://en.wikipedia.org/wiki/Mutual_information</a></p>
<p>Question. In Naive Bayesian Classification, is it better or more accurate to have less feature words?</p>
<p>I built as an independent project to analyze sentence sentiment with Naive... | g63778 | [
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<p>Say there are parameters $\theta$ such that $\theta_i > 0$ and $\sum_i \theta_i = 1$ and a model such as $p(x) = \sum_{i=1}^n \theta_i p_i(x)$ where $p_i(x)$ are fixed and defined over a domain of random variable $X$. Say $X$ is a random variable which is a categorical variable.</p>
<p>Now, say we partition $x$ ... | g63779 | [
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<p>I have a closed room. I release some bacteria in the middle of it and let it settle onto previously located plates on the floor. Once the bacteria settles I collect the plates and count up how many bacteria are on each. I then have an idea of a spatial distribution. Results might look something like the contour plo... | g14718 | [
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<p>To illustrate the problem posed by the question: Consider the problem of differentiating between consumers who belong to two different segments. I could use a naive or a sophisticated approach as outlined below. </p>
<p>The question is: what is the benefit to using the sophisticated approach?</p>
<p><strong>Naive... | g63780 | [
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<blockquote>
<p>The discrete nature of the DP makes it unsuitable for general applications in Bayesian nonparametrics, but it is well suited for the problem of placing priors on mixture components in mixture modeling.</p>
</blockquote>
<p>This quote is from <a href="http://www.gatsby.ucl.ac.uk/~ywteh/research/npbaye... | g63781 | [
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<p>I have samples of two classes which are vectors in high dimensional space and I want to plot them in 2D or 3D.</p>
<p>I know about dimensionality reduction techniques, but I need a really simple and easy to use tool (in matlab, python or a prebuilt .exe).</p>
<p>Also I wonder is representation in 2D going to be "m... | g21616 | [
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<p>Wikipedia says now, here in the introduction:</p>
<p><a href="http://en.wikipedia.org/wiki/Student%27s_t-distribution" rel="nofollow">http://en.wikipedia.org/wiki/Student%27s_t-distribution</a></p>
<p>"... then the t-distribution (for n-1) can be defined as the distribution of the location of the true mean, relati... | g63782 | [
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<p>I have a data set at hand that I don't know how to analyze it. Essentially, I have four predictors to predict one outcome. For each predictor, the data distribution is different. Two of them look linear, one of them look quadradic, and the other one seems to be at a higher order. </p>
<p>Is there a good tutorial to... | g63783 | [
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<p>I am trying to do a multi-scale analysis and I've stumbled upon, either by personal research or recommendations (as in this <a href="http://stats.stackexchange.com/questions/34803/hidden-markov-model-segmentation-of-different-proportions-of-binary-data">Q</a>), with the concept of Space-scale analysis.</p>
<p>Do yo... | g63784 | [
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<p>I need to perform a two-step calibration and I need you to tell me if I am doing that correctly. First I want to calibrate a force sensor with masses. I measure several weights and perform a linear regression of my data such as:
$$
F_1 = a_1 s_1+b_1
$$
with $F_1$ the applied force in N, $s_1$ the sensor value and $... | g41008 | [
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<p>If you analyze the same data with a t test and the nonparametric Mann-Whitney test, which do you expect to have the lower P value?</p> | g41009 | [
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<p>I have a very simple data set: a parameter (concentration of a chemical) was measured at day 0, day 1 and day 2 in three subjects (there is a control group as well, but here all the values are always 0). The results are as follows:</p>
<pre><code> S1 S2 S3
day 0 0 0 0
day 1 0 5 45
... | g63785 | [
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<p>I'm trying to run a regression analysis on a Taguchi design. I have five categorical control factors, one of them with two levels and the other four with three levels.</p>
<p>I want to generate a regression equation either based on the control factors without the levels or with the optimal levels for each factor. I... | g63786 | [
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<p><img src="http://i.stack.imgur.com/WbiL9.png" alt="enter image description here"></p>
<p>I have 10 question, based on 5 Likert scale choices.
How do I find degree of freedom here in Chi square?
Some one says use $(r-1)\cdot (c-1)$ but I think it will apply on categorical data, my data is not that one.</p> | g14765 | [
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<p>I am using R/RStudio to code a regression (and to optimize the function) over 50+ different variables. For the optimization to work I need to fit a higher order function (I am not sure to what degree I will use).</p>
<p>My question is this: is there a way in R to choose the best variables?</p> | g49682 | [
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<p>What factors make for a great statistics book? In other words, what writing styles, visualizations, explanatory methodologies, text length(!), tone, depth, etc, etc contribute to giving the audience a great education, understanding, or perhaps even entertainment? The question could perhaps also be framed as "What ad... | g63787 | [
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<p>I've been wondering something for a while. If you run a simple regression model in R and then perform a step-wise selection (it doesn't have to be the way I typed the code below), how do you extract some of the "relevant" information of the model in R suchs as Odds Ratios and/or confidence intervals? </p>
<p>The ge... | g63788 | [
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... |
<p>I am looking for a nice concise statistics book that summarizes how to do the experimental designs properly, and maybe some algorithms people in the field have discovered. What are the best books for this?</p> | g63789 | [
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<p>There are different ways to calculate the test statistic for the Wilcoxon rank sum test (quote from R help):</p>
<blockquote>
<p>The literature is not unanimous about the definitions of the Wilcoxon
rank sum and Mann-Whitney tests. The two most common definitions
correspond to the sum of the ranks of the firs... | g63790 | [
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<p>I am looking for a good tool in R or Python or any other implementation that can help to me generate sampling from hierarchical Pitman-Yor processes (HPY) (one of the recent and popular nonparametric Bayesian methods) to do language modeling.</p>
<p>Any help or pointer is appreciated.</p> | g63791 | [
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<p>I have a research design with 3 predictors and 2 mediators, tested on 2 different samples with multiple regression analysis. For my first sample (N=70) the results were:variables(mediators) entered at the second step predicted significantly the outcome, but only one of them had a significant coefficient. The IV's ha... | g21627 | [
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0... |
<p>I posted this on stackoverflow.com yesterday and its had very few views. I came across this stackexchange site and thought its got to be worth an ask:</p>
<p>I have an interesting problem and I'm sure there is an elegant algorithm with which to solve the solution but I'm having trouble describing is succinctly whi... | g21628 | [
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<p>I understand that fuzzy clustering using FCM produces a membership matrix for the set of data points we feed to it. What characteristics will an anomalous cluster produced during this method have? (Considering I only have unlabelled data)</p> | g63792 | [
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<p>I guess my question comes in two parts:</p>
<ol>
<li><p>Following a 1x7 repeated-measures ANOVA, I carried out 3 pre-planned tests. Two were t-tests between 2 of the conditions. The third is a 1x6 ANOVA (to test significance between conditions 2-7). My question is:<br>
Do I have to apply the Bonferroni correcti... | g41016 | [
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<p>Considering the scenarios of exploring data, predicting (in the range of predictors), extrapolating and explaining- for which would one need a model? When can one do without one?
[Edit] By "model" I mean a probabilistic representation of the data generating process.</p>
<p>As an example I would say, that for the pu... | g43993 | [
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<p>The below graphs are residual scatter plots of a regression test for which "normality", "homoscedasticity" and "independence" assumptions have already been met for sure! For testing the <em>"linearity"</em> assumption, although, by looking at the graphs, it can be guessed that the relationship is curvilinear, but t... | g41018 | [
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... |
<p>I have a dataset on 4 websites where I have asked whether a respondent is happy or not about each of the 4 websites.</p>
<p><strong>Website1</strong>, <strong>Website2</strong>, <strong>Website3</strong>, and <strong>Website4</strong> are column headings.
With data as <code>Happy</code> and <code>Not Happy</code> b... | g44076 | [
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0... |
<p>According to <a href="http://en.wikipedia.org/wiki/Gamma_distribution#Summation" rel="nofollow">the Wikipedia article on the Gamma distribution</a>:</p>
<p>If $X\sim\mathrm{Gamma}(a,\theta)$ and $Y\sim\mathrm{Gamma}(b,\theta)$, where $X$ and $Y$ are independent random variables, then $X+Y\sim \mathrm{Gamma}(a+b, \t... | g41019 | [
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<blockquote>
<p>A pair is concordant if the subject ranked higher on X also ranks higher on Y. The pair is discordant if the subject ranking higher on X ranks lower on Y. The pair is tied if the subjects have the same classification on X and/or Y.</p>
</blockquote>
<p>Say I have a table (e.g., $n_{11}$ is the first ... | g49394 | [
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<p>I have a very long vector, <code>x</code>, of integer values in the range [0, 1000]. I then use <code>stats::ecdf</code> to create
empirical cummulative distribution function (ECDF). Since the minimum value of <code>x</code> is 0, I expect
that <code>ecdf(x)(0)</code> would be equal to zero. However, this is not t... | g63793 | [
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<p>I am investigating a link between a random walk with drift (call it Brownian process or difusion with drift) and the CUSUM statistic.<br>
The CUSUM procedure accumulates deviations from the process mean over time, thus, if a change in the mean occurs for some reason, then the CUSUM will steadely increase over time, ... | g63794 | [
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<p><a href="http://egtheory.wordpress.com/2013/04/14/egalitarian-dilemma/" rel="nofollow">I have stochastic simulations</a> that depend on a parameter $k$. As I vary $k$ the quantities I track vary gradually and then suddenly transition to very different values and continue to vary gradually again; it seems that my sys... | g63795 | [
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<p>I'm looking for a method to identify a shortlist of potentially good 2-way interaction terms rather than trying all possible interactions. This question is similarly asked before <a href="http://stats.stackexchange.com/questions/4901/what-are-best-practices-in-identifying-interaction-effects">here</a> but in a more ... | g63796 | [
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<p>I'm trying to do dimensionality reduction using matlab princomp, but i'm not sure i'm do it right.</p>
<p>here is the my code just for test, but I'm not sure that I'm doing projection right:</p>
<pre><code>A= rand(4,3)
AMean = mean(A)
[n m] = size(A)
Ac= (A - repmat(AMean,[n 1]))
pc= princomp(A)
k=2; %number of fi... | g63797 | [
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<p>I have data from a randomized survey experiment in which each respondent was assigned to one of 4 groups, one of which can be considered a "control" or "no treatment" group. The key question asked in the survey was a binary one: i.e. each respondent was faced with a choice between two products given some stimulus ba... | g63798 | [
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<p>I would like to plot on the same graph the interaction between my continuous predictor and my categorical moderator. I know how to do it when both are categorical (<a href="http://davidmlane.com/hyperstat/A130844.html">factor interaction</a>), but don't really know how to do it when one is continuous and one is cate... | g63799 | [
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<p>Gelman and Hill have an example in their text where they analyze <a href="http://www.stat.columbia.edu/~gelman/arm/examples/girls/births.txt" rel="nofollow">this birth related dataset</a>. I understand the idea behind the analysis, but I can't verify the actual confidence interval that they get:</p>
<pre><code>To... | g21642 | [
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<p>I have a study in which 60 subjects took both drug A on one day and drug B on another. The order of drug administration was counterbalanced, such that 30 subjects took drug A on the first day and 30 took drug B on the first day. (Each subject then received the other drug on the second day.) Our dependent variable... | g63800 | [
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-... |
<p>As described previously in <a href="http://stats.stackexchange.com/questions/35173/r-software-implementation-of-combining-mixed-treatment-comparisons-and-meta-regr">this</a> post, I am currently working through issues with conducting a network meta analysis (also known as mixed treatment comparisons). For those unf... | g63801 | [
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<p>PCR in fact is regression on PC scores but not PC, but why, in so many books and tutorials, do they say something like, "in statistics, principal component regression (PCR) is a regression analysis that uses principal component analysis when estimating regression coefficients" (<a href="http://en.wikipedia.org/wiki/... | g63802 | [
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<p>I've run a chi-square test of independence on a two-way table with two categories on the rows and four categories on the columns. My $p$-value is below my chosen $\alpha$, so I may conclude that the rows and columns of this two-way table are dependent. I'm having trouble characterizing the dependence among the rows ... | g63803 | [
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0.... |
<p>I am assessing the acceptability of a sentence in a within-subjects design with two crossed factors (type of sentence, missing word). After reading each sentence, the participants answer a simple yes/no question which is my dependent variable.</p>
<p>Because a dichotomous variable is not normally distributed I am g... | g37510 | [
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... |
<p>I have a data set in which two raters have each rated N samples using a 5-point ordinal rating scale. My primary interest is in whether these two raters make significantly different use of those ratings (i.e. I believe I'm interested in whether the item is subject to differential item functioning, DIF).</p>
<p>Ther... | g63804 | [
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<p>Ok, I have searched and searched and just have no clue where to start. First, what I would like to do is produce a QQ-plot (or even a readable residual plot) to look at the fit of my model. I guess I just don't understand how the parameters that go into <code>qnbinom()</code> are obtained from the output of <code>... | g63805 | [
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0.089553125202655... |
<p>I work for an environmental health nonprofit and I have moderate expertise in statistics. We want to estimate the total number of toxic industrial waste sites within a small African country. I would love to hear your thoughts on how we should start. At this stage, if you can recommend a book, an idea, or a general s... | g63806 | [
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0.009004664607346058,
0.004363174084573984,
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0.048731863498687744,
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<p>Suppose we want to see whether $X$ and $Y$ are bivariate normal. Does it matter whether we plot $X$ and $Y$ on a QQ plot versus $f(X)$ and $f(Y)$? For example, if we plot $\log X$ and $\log Y$ on a QQ plot, should that tell us whether $X$ and $Y$ are bivariate normal?</p>
<p>If $X = A/B$ and $Y = C/D$ and we want t... | g21647 | [
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<p>I am looking for a way to find the probability that there is no difference between a matched pair of binary data. I don't want to know whether the difference is statistically significant, I want to know the probability of the hypothesis that there is no difference. For statistical significance I would usually use th... | g63807 | [
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-0.032533083111047745,
-0.009672838263213634,... |
<p>I was wondering whether the Breusch-Godfrey test on panel data has the same effect as Wooldridge test (see <a href="http://www.stata-journal.com/sjpdf.html?articlenum=st0039" rel="nofollow">http://www.stata-journal.com/sjpdf.html?articlenum=st0039</a>) and I would like to know which test is better. It seems to me th... | g63808 | [
0.06404823809862137,
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<p>As I began my study of sufficient statistics I stumbled upon a definition that puzzled me. The conditional probability distribution of the sample values given an estimator $\hat{\Theta}=\hat{\theta} $ is given by </p>
<p>$$ f\left( x_1,x_2,\ldots,x_n|\hat{\theta} \right) = \frac{f \left(x_1,x_2,\ldots,x_n,\hat{\the... | g63809 | [
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<p>I have a dataset of the wealth of 10 different countries in the world since 1800, one data point per year. </p>
<p>Let's say I have noticed that when the wealth of a country goes above $1,000,000, this country goes from state A to state B (no matter what those states really mean).</p>
<p>What kind of statistical t... | g63810 | [
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<p>I have run some regression models that examine the effect of variable X (a 15 point continuous scale) on Y (a binary variable - not perform/perform a particular behaviour) using logistic regression.</p>
<p>For the sake of this example, let’s say that the OR in one of the models is 1.08. I can argue that for each ex... | g21651 | [
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<p>I came across this journal <a href="http://www.hks.harvard.edu/fs/aabadie/ccsp.pdf" rel="nofollow">http://www.hks.harvard.edu/fs/aabadie/ccsp.pdf</a> which basically uses Synthetic Control Method (SCM) to estimate the difference between the impact on a variable when an event happens versus when it does not happen (w... | g63811 | [
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<p>I have a distance matrix that I want to cluster. What methods can I use to cluster the elements just based on the distance matrix (beside hierarchical clustering)? </p> | g49683 | [
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<p>There is an example on how to run a GLM for proportion data in Stata here: <a href="http://www.ats.ucla.edu/stat/stata/faq/proportion.htm" rel="nofollow">http://www.ats.ucla.edu/stat/stata/faq/proportion.htm</a></p>
<p>The IV is the proportion of students receiving free or reduced priced meals at school. The stata ... | g63812 | [
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<p>Can you do a t-test or ANOVA between 2 or 3 groups respectively if one of those groups has a sample size of 2? Are the results interpretable in the same way as with larger sample sizes(n=4,5,6?). If you can provide any references to read more about very small sample size statistics, that would be helpful.</p> | g49489 | [
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<p>I'm analyzing datasets of users that range in size from 5,000 users up beyond 150,000 users, and each of these users have at least 32 data-points (sometimes more, sometimes a few less) with (about) 5 possible responses for each point. Each of these users have a single value that evaluates how they contribute as a hi... | g28739 | [
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<p>For a 3-class classification problem the theoretical chance level is 33.33%. What should be the minimum accuracy (in percentage) to be above chance level f0r a significance intervals of 5% and 1%. And how to calculate it ?</p> | g28741 | [
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<p>I am looking for the standard error for the distribution of the difference in proportions for hypothesis testing when the null hypothesis is that the two proportions are different by a constant.</p>
<p>Let's say that: $H_0: {p}_1 = {p}_2 + c$. Then I've seen that $\sigma_{\hat{p}_1 - \hat{p}_2}=\sqrt{\frac{\hat{p... | g63813 | [
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<p>I know that it is possible when you realize a multiple linear regression to calculate the confidence interval on the R-squared and on the adjusted R-squared. Does somebody know how to do it with R?</p> | g63814 | [
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<p>I'm basically wondering whether log transformed data or raw values should be used to calculate: </p>
<ul>
<li>effect sizes </li>
<li>change scores </li>
<li>the standard deviation (SD) for the precondition </li>
</ul>
<p>I know that SD of log transformed data doesn't back transform nicely and so does this affect... | g21666 | [
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<p>Suppose I have a sorted list of 30 numbers with display exponential trend (a few numbers are fairly large, and a lot of them are relatively small). </p>
<p>Now I am selecting a random index (a realization from DISCRETE-UNIFORM(0, 29)) and remove that entry from the list.</p>
<p>Now, my goal is that the next number... | g63815 | [
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<p>I have data for two input variables x_1 and x_2 and one output variable y. The two input variables seem to have a nonlinear relationship with y. Here are the plots
<img src="http://i.stack.imgur.com/k9oqc.png" alt="enter image description here"></p>
<p><img src="http://i.stack.imgur.com/BSxRs.png" alt="enter imag... | g63816 | [
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0.003071422455832362,
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... |
<p>I have correlated data and am using a logistic regression mixed effects model to estimate the individual level (conditional) effect for a predictor of interest. I know that for standard marginal models, inference on model parameters using the Wald test is consistent for the likelihood ratio and score tests. They are... | g63817 | [
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0.020379120483994484,
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0.0129... |
<p>I have an online k-means algorithm following this scheme:</p>
<pre><code>Let x a new data-point, and c the nearest cluster center
if( distance(x, c) > threshold )
x becomes a new cluster center
else assign x to c
</code></pre>
<p>In order to speed up the search for nearest center, is it possible to have a hi... | g63818 | [
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0.039598118513822556,
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0.05547979474067688,
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<p>I want to apologise in advance if this question seems a bit vague, but I'm not sure how is the best way to ask it. On the other hand I'm pretty sure this must be a common scenario so I hope to get answers !</p>
<p>I have a dataset that looks like this</p>
<pre><code>ID time treatment
1 1 A
2 1 A
3 2 ... | g63819 | [
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0.022255584597587585,
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0.09546085447072983,
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0.019405636936426163,
0.03100033663213253,
0.04797571897506714,
0.07734609395265579,
0.01345... |
<p>I have two graphical models that have significant overlap in the random variables they are modeling. Is it possible to use samples from one graphical model to avoid sampling as much from the other graphical model?</p>
<p>As an example can I use samples from an empirical bayes approach in estimating the distribution... | g63820 | [
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0.022856689989566803,
0.07324770092964172,
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0.01812526024878025,
... |
<p>Does any know how to draw a graph like this:</p>
<p><img src="http://i.stack.imgur.com/KRfmE.gif" alt="http://upload.wikimedia.org/wikipedia/commons/b/b1/Ivsrf.gif"></p>
<p>Which programs can do that? I'm a developer so I've no problem on formatting a complex files so that a software can handle it.</p> | g63821 | [
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<p>In text classification, I have a training set with about 800 samples, and a test set with about 150 samples. The test set has never been used, and waiting to be used until the end.</p>
<p>I am using the whole 800 sample training set, with 10 fold cross validate while tuning and tweaking classifiers and features. Th... | g63822 | [
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<p>I am trying to do a meta-analysis using Hedges' G as the effect size. </p>
<h3>Questions</h3>
<ol>
<li>Some of the studies have different groups but the same control group. How does this change the computation and pooling of effect sizes?</li>
<li>How do I calculate a weighted effect size for each study so that I ... | g37802 | [
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0... |
<p>I am looking to find out how accents could/would be detected by a programme, I haven’t as of yet undergone an experiment into detecting or observing anything noticeable about recorded accents. I am not sure a frequency/harmonic analyses will reveal anything. Trying to find any literature review on the subject is sad... | g21681 | [
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0.0168... |
<p>Can you just eyeball the Hosmer-Lemeshow test (e.g. just look at observed and expected values in each group and see if they agree more or less)? Even if the Hosmer-Lemeshow statistic is significant...can I still say the model fits the data well for my purposes just by observing the observed and expected values in ea... | g21682 | [
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0.0046829036436975,
0.07005923986434937,
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0.05803483724594116,
0.035134... |
<p>Imagine I have a test for a disease that returns either a positive or a negative result. I administer the test to one group twice in a single session; in another group, I administer it twice with two weeks separating the tests. The hypothesis is that the tests taken at the same time will be more consistent with ea... | g49655 | [
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0.0... |
<p>There is a <a href="http://stats.stackexchange.com/q/66709/30540">duplicate</a>, and the reason why I still ask this question is that, the answer to that duplicate doesn't answer the question well.</p>
<p>The Gaussian Process prior is $$u\sim GP(0,k(x,x'))$$, I tend to write it this way, $$p(u)=N(0,K)$$.
The observ... | g63823 | [
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-0.024899372830986977,
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0.07786361128091812,
0.019900629296898842,
-0.... |
<p>I am working on making a RPG and am trying to understand the statistics of the core mechanic so I can determine how effective leveling and bonuses will be.</p>
<p>Right now the core mechanic is a skill die based mechanic where you roll a d4, d6, d8 or d10 based on your skill opposed by either a DC set by the story ... | g44392 | [
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0.012502139434218407,
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<p>I encountered a real-world problem where I want to model the effectiveness of various advertising media of a brand (measured in terms of sales). Basically, the Y in this case is weekly sales, and the X's are media investments in newspaper, magazine, display boards, tv, radio and online, as well as incentive, which i... | g63824 | [
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0... |
<blockquote>
<p>(1 pt) In a large class, there were 230 students who wrote both the midterm and the final exam. The standard deviation of the midterm grades was 11, and that of the final exam was 16. The correlation between the grades on the midterm and the final was 0.66.
Based on the least squares regression line... | g63825 | [
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<p>A report states that 15% of men in the US are left handed. If a random sample of 125 men contains only 10 men who are left handed, is it reasonable to assert that 15% of all males are left-handed is unlikely? Or is that particular random sample unlikely? </p>
<p>We can see here that the sample proportion is $\hat{p... | g63826 | [
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0.021414611488580704,
0.02269008383154869,
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-0.0299057... |
<p>Wikipedia <a href="http://en.wikipedia.org/wiki/Kurtosis#Sample_kurtosis" rel="nofollow">http://en.wikipedia.org/wiki/Kurtosis#Sample_kurtosis</a> calculates the sample excess kurtosis as </p>
<pre><code>length(x) * sum((x - mean(x))^4)/(sum((x - mean(x))^2)^2) - 3
</code></pre>
<p>On the other hand, I learned fro... | g63827 | [
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-0.004651894327253103,
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0.005143224261701107,
0.055184151977300644,
... |
<p>I want to use logistic regression for binary classification on a dataset. I have 14 features in the dataset, and all but one are continuous. I have one categorical variable that represents a country, and there are 10 different countries in the dataset. Is there any way I can incorporate this categorical variable ... | g49684 | [
0.008771850727498531,
0.022562909871339798,
0.0021387403830885887,
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-0.040066372603178024,
0.008204138837754726,
0.033108294010162354,
0.03926674649119377,
... |
<p>How do I find the variance for</p>
<p>$z_n=\prod_{i=1}^n(1-k_i e^{a_i x})$</p>
<p>where $x$ is the random variable with a normal distribution and is the same for all $i$ (which is a subscript for time dependency which is not dependent with $x$).</p>
<p>I have tried using the method by <a href="http://www.jstor.or... | g63828 | [
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0... |
<p>Suppose I am given a possibly biased coin, which turns up heads an unknown fraction $p$ of the time. </p>
<p>Initially I flip the coin 10 times (e.g. generating data = TTHTTHHTHH). </p>
<p>Next, I have to flip the coin repeatedly until I get 2 heads in a row. Let the number of flips I perform before getting 2 head... | g21694 | [
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-... |
<p>I am working with EEG and now I am trying to compare coherence for two groups of individuals. Problem is coherence is dependent on length of signal but I have signals with different length for each individual. So I decided to divide my signals on equal pieces and randomly choose fixed number of pieces for each indiv... | g63829 | [
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0.0017054654890671372,
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... |
<p><strong>Is it possible to use the mixed-models approach to test if the mean of a sample is significantly different from zero?</strong></p>
<p>I know that mixed models, with crossed random effect for target, and subject, are an increasingly popular way of analyzing the difference between two groups in psychological
... | g63830 | [
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<p>I have this algorithm that I'm implementing that I need to change to give it a better accuracy. To give you an idea of the problem,
I have a a bunch of lists that contain items and all items in these lists have been given ratings by users. I need to compute the a weight of these list such as the higher the weight t... | g21697 | [
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0.... |
<p>I have two matrices corresponding to the same set of $n$ samples, with $j$ and $k$ variables, respectively ($j > 10000$, $k > 10000$). $X$ is an $n \times j$ matrix and $Y$ is an $n \times k$ matrix.</p>
<p>I'm interested to know what proportion of the overall variance of $Y$ can be explained by $X$. The ulti... | g63831 | [
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0.04... |
<p><em>I'm quite new to this topic, so this is probably very basic for most of you:</em></p>
<p>I want to analyse the relationship of multiple variables via partial correlation as an alternative for a regression analysis. I don't only want to find out how the independent variables relate to the dependent variable but ... | g63832 | [
0.01716821826994419,
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-0.034252941608428955,
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-0.018093694001436234,
0... |
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