question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>What are the best methods for fitting the 'mode' of data sampled from a continuous distribution?</p>
<p>Since the mode is technically undefined (right?) for a continuous distribution, I'm really asking 'how do you find the most common value'? </p>
<p>If you assume the parent distribution is gaussian, you could bi... | g68187 | [
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<p>I'm having a hard time understanding how to use confidence intervals for hypothesis testing. I've seen examples to reject a null hypothesis, but don't understand how to use a one-sided confidence interval to show significance. </p>
<p>If you have two samples, x and y, how you would you use a one sided confidence in... | g982 | [
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<p>Here is an example I am trying to copy from a text that I have. No idea how to proceed.</p>
<pre><code>car.noise <- data.frame( speed = c("idle", "0-60mph", "over 60"), chrysler = c(41,65,76),
bmw = c(45,67,72), ford = c(44,66,76), chevy = c(45,66,77), subaru = c(46,76,64))
mcar.noise<- melt(car.noise, id.va... | g68188 | [
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<p>I want to do graph clustering on a large dataset (A graph with 600,000 Nodes and tens of millions of edges). I read about Markov clustering. I saw this algorithm involved the calculation of a stochastic matrix and its powers. Therefore, I was wondering whether it could be used here? Otherwise, what algorithm do you ... | g68189 | [
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<p>I have two independent samples of observations. From each sample I produce a statistic. Let's denote these as $\theta_1$ and $\theta_2$. I'd like to test the hypothesis that $H_0: \Theta_1=\Theta_2$, but I have these two constraints:</p>
<ul>
<li>There is no analytical estimate of the distributions of $\theta_1$ an... | g68190 | [
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<p>I have a question regarding statistical evaluation of the AUC.
In their paper (<a href="http://www.jstor.org/stable/2531595" rel="nofollow">http://www.jstor.org/stable/2531595</a>), DeLong et al. describe a method to evaluate AUC curves. (Another good explanation can be found in the book "Statistics with Confidence:... | g28078 | [
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<p>I'm working on LibSVM and I'm using linear kernel. But i have a problem with C parameter, it does not affect accuracy during test set! Is it possible?</p>
<p>I send a picture with the distributions of the two classes and the separator line. This line did not change when I changed C. I have no idea why! :-( <img src... | g68191 | [
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<p>I'm trying to solve a problem where the goal is to find an association between children's cortisol values (<code>y</code>) against their mother's weekly cortisol averages (<code>x1</code> to <code>x6</code>) and gender (<code>z</code>). After conducting model selection strategies in R (all subset regression, backwar... | g68192 | [
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<p>I suspect that most users of statistical tools are ancillary users (folks who have had little to no formal training in statistics). It’s very tempting for researchers and other professionals to apply statistical methods to their data simply because they have seen it “done before” in peer-reviewed papers, grey liter... | g48913 | [
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<p>I have the population which is split into three classes; A, B and C. We know that the number of observations in each class is Na, Nb and Nc respectively. Assuming that my observations are binary distributed how can I specify (with a formula) probability of observing not more than P positive outcomes.</p> | g68193 | [
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<p>I am using quantile regression (for example via <code>gbm</code> or <code>quantreg</code> in R) - not focusing on the median but instead an upper quantile (e.g. 75th). Coming from a predictive modeling background, I want to measure how well the model fits on a test set and be able to describe this to a business user... | g68194 | [
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<p>(I hope this question may be too easy for some experts here). It is well-known that if $X$ is normal rv and $Y$ is a chi-square rv, then $Z=X/\sqrt{Y/n}$ follows student's $t$ distribution, where $n$ is the degrees of freedom of $Y$, and $X$ and $Y$ need to be independent.</p>
<p>However, what comes if $X$ and $Y$... | g28083 | [
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<p>I have an implementation of the Griddy Gibbs sampler, but my observations on which I'm conditioning model parameters are too many in number, thus the likelihood underflows quickly, even with a log transformation.
Sequential updating holds if one is using conjugate priors, since the posterior can be found analytical... | g68195 | [
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<p>If i have a non-stochastic model that predicts the following dataset:</p>
<blockquote>
<p>[.2, .2]</p>
</blockquote>
<p>and the actual dataset found empirically (averaged over participants) is</p>
<blockquote>
<p>[.3, .3]</p>
</blockquote>
<p>How would I determine the likelihood of the model?</p>
<blockquot... | g28086 | [
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<p>I am designing my study, but I am a little stuck in which test I eventually should use. I have a between-subject design with 6 conditions (let's say A, B, C, D, E, F), with each having 6 responses (let's call these a, b, c, d, e, f), on a 7-point scale:</p>
<pre><code>IV (condition) -> DV
A -> a, b, c, d, e, ... | g68196 | [
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<p>I'm concerned about treating my data as gold, especially in areas of low data support, so I would like to apply <a href="http://en.wikipedia.org/wiki/Additive_smoothing" rel="nofollow">additive smoothing</a>. I'm then doing several things with this data, and one of them is <a href="http://en.wikipedia.org/wiki/Pear... | g68197 | [
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<p><strong>Background</strong></p>
<p>I am designing a Monte Carlo simulation that combines the outputs of series of models, and I want to be sure that the simulation will allow me to make reasonable claims about the probability of the simulated outcome and the precision of that probability estimate.</p>
<p>The simul... | g68198 | [
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<p>I'm trying to use the <code>nnet</code> library in R, and can't seem to work out how to use the <code>reltol</code> parameter. It says in the docs:</p>
<blockquote>
<p>Stop if the optimizer is unable to reduce the fit criterion by a factor of at least 1 - reltol.</p>
</blockquote>
<p>I assume this means that if ... | g28088 | [
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<p>Very basic question, I suspect. It's sort of the inverse of <a href="http://stats.stackexchange.com/questions/5092/representative-sampling">this one</a>, and the same disclaimers about my own ignorance apply, but here goes:</p>
<p>I have a sampling technology. I know the total population, and I know the number of s... | g68199 | [
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<p>I want to get a confidence interval of a function of some parameters. for example, from the data I estimate parameters of Pareto. Now I want to get 95% CI for 90th quantile (it's a function of parameters of Pareto), so I would need standard error. </p>
<p>I know delta method is one option. For simulation method, I ... | g68200 | [
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<p>I thought heavy tail = fat tail, but some articles I read gave me a sense that they aren't.</p>
<p>One of them says: heavy tail means the distribution have infinite jth moment for some integer j. Additionally all the dfs in the pot-domain of attraction of a Pareto df are heavy-tailed.
If the density has a high cen... | g17573 | [
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<p>I learned in statistics basic course that sometimes one can make reasoning about the data by making graphical plots, like testing outliers or P-P-plot or Q-Q-plot. But are there some test which measures the same things by numbers? Like what can one do if he or she have to analyze some data in a computer that don't h... | g28092 | [
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<p>I am running a dlog-dlog (difference of logarithm*) regression and I want to convert the coefficients into marginal effects. I know that it's different from a log-log regression, in which the coefficients directly give us the elasticities. </p>
<p>How can we interpret the coefficients from a dlog-dlog regression? <... | g48925 | [
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<p>What could be some issues if the distribution of the test data is significantly different than the distribution of the training data and why is that?</p>
## Edit 1 ##
<p>The training and testing sets came from different processes. I was thinking if I use a set of data, that is say normally distributed, to train a... | g68201 | [
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<p>I am a newbie at R and I'm stuck at the following code</p>
<pre><code>$y=c(2.5,6.0,6.0,7.5,8.0,8.0,16.0,6.0,5.0,6.0,28.0,5.0,9.5,6.0,4.5,10.0,14.0,3.0,4.5,5.5,3.0,3.5,6.0,2.0,3.0,4.0,6.0,5.0,6.5,5.0,10.0,6.0,18.0,4.5,20.0)
x2=c(650,2500,900,800,3070,2866,7500,800,800,650,2100,2000,2200,500,1500,3000,2200,350,1000,6... | g68202 | [
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<p>On slide 32/85 of <a href="http://www.robots.ox.ac.uk/~vedaldi/assets/svm-struct-matlab/tutorial/ssvm-tutorial.pdf" rel="nofollow">this tutorial on structured SVM learning</a>, the author formulates binary SVM classification in terms of the structured SVM just introduced.</p>
<p>Why is there a constant factor of $1... | g8536 | [
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<p>So I have a large dataset, and I was wondering what the best way to conduct statistical analysis of it is. I'm very green in terms of statistical methods, but I learn quickly. Basically, each item has a couple attributes, and each attribute has several possibilities. Each item has their specific attribute set-up in ... | g68203 | [
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<p>I am trying to find the optimal strategy for a game where the goal is to pick a number of items where the profit is uncertain but the weights are set. Each round of picking is a specific point in time, and each round is partially independent from the past (think sports games). This is basically a version of the knap... | g68204 | [
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<p>I recently learned about a principle of probabilistic reasoning called "<a href="http://ai.eecs.umich.edu/people/wellman/pubs/pami93.html">explaining away</a>," and I am trying to grasp an intuition for it.</p>
<p>Let me set up a scenario. Let $A$ be the event that an earthquake is occurring. Let event $B$
be the ... | g68205 | [
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<p>I have read many threads here on how to interpret coefficients in a regression where the predictor and the dependent variable are log-transformed. Most give an answer for a one or ten percent change. However, I am not sure whether I am right about interpreting other changes.</p>
<p>I have a beta coefficient of -0.5... | g68206 | [
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-0.00... |
<p>I am carrying out a study to find out meteorological patterns using daily met observations including around 30 met parameters (each day is a case with 30 variables). My methodology includes carrying out a PCA:</p>
<ol>
<li><p>To reduce 30 variables to smaller number of PCs.</p></li>
<li><p>Find out the PC scores fo... | g68207 | [
0.025581495836377144,
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0.004358215257525444,
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0.03684961423277855,
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<p>When I took courses in theoretical statistics as an undergrad 10 years ago, we used <em>Modern Mathematical Statistics</em> by Dudewicz and Mishra. I find myself referring back to the book now and am reminded some of the code examples are in assembly for an IBM 370. While quaint, I cannot help but feel this is som... | g168 | [
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0.011832178570330143,
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0.0... |
<p>My situation is this:</p>
<ul>
<li>I am comparing two cohorts</li>
<li>I have matched the two cohorts on all of the factors that I am interested in</li>
<li>The two cohorts are already balanced on all of the factors that I would include in a regression</li>
</ul>
<p>Questions:</p>
<ul>
<li>Is it appropriate to ju... | g11525 | [
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0.003231016220524907,
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0.03513599559664726,
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-0.06041184067726135,
0.04746951162815094,
-0.011823851615190506,
0.00980331376194954,
0.... |
<p>I find resources like the <a href="http://matthias.vallentin.net/probability-and-statistics-cookbook/">Probability and Statistics Cookbook</a> and <a href="http://www.google.com/url?sa=t&source=web&cd=2&ved=0CC4QFjAB&url=http://cran.r-project.org/doc/contrib/YanchangZhao-refcard-data-mining.pdf&r... | g49363 | [
0.04523763060569763,
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0.03606250882148743,
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-0.010106352157890797,
0.053106408566236496,
-0.010126325301826,
0.10546997934579849,
0.04... |
<p>I am doing some exploratory data analysis in the <a href="http://www.heritagehealthprize.com/" rel="nofollow">Heritage Health Prize </a>, and have come across a weird error using R's caret package. In the dataset, I've created a dataframe counting how many times a patient (by <code>MemberID</code>) has visited a spe... | g68208 | [
-0.020723888650536537,
0.005003191530704498,
-0.007757526356726885,
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0.022279690951108932,
0.05017406493425369,
0.07465565204620361,
-0... |
<p>I've recently calculated a hazard ratio doing a multi variable Cox regression analysis (Kaplan Meier) for an assignment. Part of my feedback was to adjust the hazard ratio to a 'crude ratio'.</p>
<p>How do I do that? I'm using SPSS 19/PASW.</p> | g68209 | [
0.002954714698716998,
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0.061290379613637924,
0... |
<p>I have a physical signal (for example, <code>Temperature</code>, <code>Humidity</code>) which is sampled at discrete times. I wanted to know how to compute the temporal correlation between "a value of the signal" and "another group of values in the same signal, but acquired previously". I found this <a href="http://... | g68210 | [
0.03231818601489067,
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<p>I have a time series data (1 minute and sometimes 5 minute data) data I would like use <code>forecasting</code> package to forecast couple hours ahead.</p>
<p>Here is my data:</p>
<pre><code>dput(head(p,20))
structure(list(time = structure(c(1373889420, 1373889480, 1373889540,
1373889600, 1373889660, 1373889720, ... | g68211 | [
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0.0029945976566523314,
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0.04142629727721214,
0.015667730942368507,
0.043791525065898895,
-... |
<p>I once heard some statements regarding the relationship between ARMA and AR process, such as</p>
<pre><code>An average of severl lags of an autoregression forms an ARMA process
</code></pre>
<p>or </p>
<pre><code>A weighted mixture of lags of an AR(P) model is ARMA
</code></pre>
<p>I am not very clear about the... | g68212 | [
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0.019261792302131653,
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0.0450... |
<p>I'm a marketer trying to understand the math involved in A/B testing. I've come across a <a href="http://usereffect.com/split-test-calculator" rel="nofollow">tool</a> that estimates how many more samples are required to reach significance for a test that's already begun. When you enter your test results thus far, it... | g68213 | [
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<p>Say we have a batch of data we use to learn an SVM, a Regressor, etc.</p>
<p>And we use the learned model to do online classification, the learning is not done online, the online part is only the processing.</p>
<p>How do we go about Normalization, Whitening, Rescaling, etc </p>
<p>Since most of these techniques ... | g28106 | [
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0.05363108590245247,
0.12575627863407135,
0.0520... |
<p>Suppose I have the following ACF and PACF (<a href="http://uploadeasy.net/upload/cygrd.rar" rel="nofollow">data</a>:
<img src="http://i.stack.imgur.com/A7B44.png" alt="ap">
I want to fit an ARMA-GARCH process. Currently I want to do the first step, specify the mean equation. The first model just uses a constant $\mu... | g48942 | [
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0.04699154943227768,
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0.0307617224752903,
0.03841862455010414,
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-0.004548018332570791,
-0.03031991980969906,
0.05210471898317337,
0.055589571595191956,
-0.0441... |
<p>Are there any packages that let me estimate panel GARCH models in R?</p>
<p>I have looked extensively in Google but have not found anything.</p> | g68214 | [
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0.02166818641126156,
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0.031249037012457848,
0.008475752547383308,
0.046... |
<p>I have designed a survey with multiple choice answers. Each question contains same set of answers </p>
<ul>
<li>Strongly agree </li>
<li>Agree </li>
<li>Disagree </li>
<li>Strongly disagree</li>
<li>Don't know</li>
</ul>
<p>There are 25 questions and questions are grouped into 5 areas. I need to analyze each area.... | g587 | [
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0.009859050624072552,
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0.0249297507107257... |
<p>Happy New Year to all of you.</p>
<p>I have a question regarding the interpretation of the output I get by fitting a GEE model in R. Attached is the picture of the output I get:
<img src="http://i.stack.imgur.com/3LhaW.png" alt="enter image description here"></p>
<p>1) The first column, Estimate, is obviously the ... | g68215 | [
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0.010749534703791142,
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0.017024459317326546,
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0.... |
<p>I was trying to figure out whether or not the distribution of a biomarker came from heterogeneous populations. Analyzing the data with <code>normalmixEM</code> in the <code>mixtools</code> package in R, I got two distributions, but the histogram was unimodal and seemed to be homogeneous. (Sorry, I cannot post an ima... | g17703 | [
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0.03521084040403366,
0.03788488730788231,
... |
<p>I want to look at the acf and pacf of my data, to identify the model for my mean equation, so I want to fit an ARMA for my mean equation and later on model the conditional variance by a ARCH/GARCH (I know I have to do jointly model estimation). In the first step I want to look at the ACF and PACF for identifying, I ... | g44228 | [
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0.024049455299973488,
0.05574754625558853,
0.06292197108268738,
0.0... |
<p>I am experimenting with WEKA and I'm trying to understand the impact of k in cross-fold validation. It seems reasonable to me that the higher k is, the more accurate the classifier will be (with respect to the train/test data, that is). </p>
<p>This doesn't seem to be the case when I am varying that parameter. W... | g68216 | [
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0.009919515810906887,
0.017350278794765472,
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0.04828033596277237,
0.07241205871105194,
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0.004119348246604204,
0.011367079801857471,
0.014760937541723251,
0.07940065115690231,
0.038... |
<p>This query ties a lot of my interests in rating sports teams together, because as I’ve mentioned before I do a version of the Kenneth Massey method (as per his 1997 thesis <a href="http://masseyratings.com/theory/massey97.pdf" rel="nofollow">http://masseyratings.com/theory/massey97.pdf</a>) of rating Sports Teams. I... | g68217 | [
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0.023800205439329147,
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<p>I am trying to program out a couple of statistical formulas with python. I am not concerned with efficiency or the fact that there already are tools to calculate the values, but I am doing it to increase my understanding of statistics.</p>
<p>I tried setting up the Student T CDF, but I have no clue how to even star... | g28112 | [
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<p>A coin is tossed 900 times and heads appeared 490 times. Does the result support the hypothesis that the coin is unbiased?</p> | g68218 | [
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0.017127325758337975,
-0.0171... |
<p>I'm trying to obtain the Jeffreys' prior for a negative binomial distribution. I can't see where I go wrong, so if someone could help point that out that would be appreciated.</p>
<p>Okay, so the situation is this: I am to compare the prior distributions obtained using a binomial and a negative binomial, where (in ... | g28114 | [
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0.0514124259352684,
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<p>I have not used my stats in a while and was interested in how the group would handle the following:</p>
<p>I have a multi-year insect data set that has irregularities in trapping effort, trap type and area of trap size within a specific trap type. I am interested in obtaining measures of relative abundance, dominan... | g28115 | [
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0.05311634764075279,
0.011689472943544388,
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0.031477149575948715,
0.03... |
<p>I am using the Kolmogorov–Smirnov two-sample test to compare distributions, and I noticed a $p$-value is frequently reported as the test statistic. How is this $p$-value determined? I know it's the probability of obtaining a result at least as large as the one obtained, but how is this $p$-value determined giv... | g48954 | [
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0.040059108287096024,
0.025010690093040466,
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-0.038404759019613266,
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0.012785738334059715,
0.06255894154310226,
... |
<p>I'd like to get into C++ for solving statistical problems. At the moment I should learn the basics, in particular things related to matrix computation (svd decomposition and the like), numerical derivatives, and so on. </p>
<p>I hope somebody out there is willing to suggest source materials (both books and websit... | g68219 | [
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0.09169583022594452,
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<p>I have data for motor vehicle crashes by hour of the day. As you would expect, they are high in the middle of the day and peak at rush-hour. ggplot2's default geom_density smooths it out nicely</p>
<p>A subset of the data, for drink-drive-related crashes, is high at either end of the day (evenings and early morni... | g28118 | [
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0.04671211168169975,
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<p>I know that the regression coefficient of $Y$ and $X$ is defined as </p>
<p>$$\beta(Y,X) = \frac{\mathrm{Cov}(X,Y)}{\mathrm{Var}(X)}$$</p>
<p>Does this expression also hold in a multivariate regression with $Y$, $X$ and $Z$ as additional explanatory variable? </p> | g68220 | [
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0.06898275762796402,
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0.... |
<p>I have recently started working on the unscented Kalman filter. I coded the numerically stable version (i.e., square root Kalman filter) and used MATLAB for implementing. In the final update step, where we update the state covariance matrix using <code>cholupdate</code> I get an error.</p>
<pre><code>Pk = cholupdat... | g28119 | [
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0.017697211354970932,
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0.0019704143051058054,
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0.04833376407623291,
0... |
<p>I'm building a series of hierarchical models using R and JAGS, linked using the R2jags library. The runs are fairly long -- from several hours to several days. I've had the sad experience of running some chains that did not converge. In that case, is there a way to extend the chain, rather than starting over?</p> | g28120 | [
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... |
<p>How do I define the distribution of a random variable $Y$ such that a draw from $Y$ has correlation $\rho$ with $x_1$, where $x_1$ is a single draw from a distribution with cumulative distribution function $F_{X}(x)$? </p> | g68221 | [
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0.03357886150479317,
-0.0... |
<p>We teach supplementary lessons in nearly two dozen local schools, and have two data sets of approximately four hundred records each from pre-post tests given at these schools. Each record contains pre and post values (correct, incorrect) for questions on 12 topics as well as whether or not there was an intervention ... | g28122 | [
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0.056635718792676926,
0.010496395640075207,
-0.010024112649261951,
0.049751948565244675,
-0.011516190133988857,
0.0369284451007843,
0.... |
<p>I simulated my data successfully in R by applying the R codes below.
However, I need to simulate errors separately for each different Y outcome by using covariance method in R.</p>
<p>I don't know how to use covariance to simulate errors in R.</p>
<p>Could you help me about this problem?</p>
<p>Thanks</p>
<pre><... | g68222 | [
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<blockquote>
<p>Suppose that the chain is intitially in state $1$, i.e $P(X_0 = 1) = 1$. Let $\tau$ denote the time of first return to state $1$, i.e</p>
<p>$$\tau = \min\{n > 0: X_N = 1\}.$$</p>
<p>Show that </p>
<p>$$P(\tau = k) = (0.5)^{k-1}, k = 2, 3, ...$$</p>
</blockquote>
<p>State $1$ only c... | g45204 | [
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0.007803... |
<p>I'd like to know how to calculate the sample size needed for comparing the "change from baseline" scores between two groups?</p>
<p>Thank you in advance for your consideration</p> | g38214 | [
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<p>I am trying to perform a latent class growth analysis (LCGA) and/or growth mixture models (GMMs) in R. The data I am using is an increasing number of forks of git repositories (discrete variable, not categorical), as you can see in this <a href="https://github.com/aronlindberg/latent_growth_classes/blob/master/outpu... | g28126 | [
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<p>The qq-plot can be used to visualize how similar two distributions are (e.g. visualizing the similarity of a distribution to a normal distribution, but also to compare two artibrary data distributions). Are there any statistics that generate a more objective, numerical measure that represent their similarity (prefer... | g48971 | [
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-0.0... |
<p>I would like to ask a (probably very simple) question with regards to multiple linear regression.</p>
<p>I have an experimental formula in the form:</p>
<p>$$
Y \sim \frac{a_0 \cdot X_0}{(a_1 \cdot X1) * (a_2 \cdot X_2)}
$$</p>
<p>and I want to set up a linear model which fits the $a_i$ coefficients so as to maxi... | g68223 | [
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<p>In my textbook I often see a quadratic term in the regression. For example let's say I have the regression model: $\log(\mathrm{wage})=\beta_0+\beta_1\mathrm{educ}+\beta_2\mathrm{exp}+\beta_3\mathrm{exp}^2+\varepsilon$. Why is it so common to put the squared term in there? Here's a quote from my book:</p>
<blockquo... | g68224 | [
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<p>Does the use of metric spaces to describe the support of a random variable provide any greater illumination? I ask this after reading about how metrics spaces have been used to unify the mathematical measure theoretic nature of probability and the physical intuition that most associate with probability. You can read... | g832 | [
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<p>I have calculated the repeatability of individuals' responses to a stimulus using the methodology of <a href="http://www.univet.hu/users/jkis/education/Kutatastervezes/Lessells_Boag_Auk_87_Unrepeatable_repeatabilities_-_a_common_mistake.pdf" rel="nofollow">Lessells & Boag (1987) Auk 104:116</a>, where repeatabil... | g37995 | [
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0.022... |
<p>What approaches are there to perform FA on data that is clearly ordinal (or nominal for that matter) by nature? Should the data be transformed our are there readily available <code>R</code> packages that can handle this format? What if the data is of a mixed nature, containing both numerical, ordinal and nominal dat... | g68225 | [
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<p>I have been comparing two packages that are calculating generalised hyperbolic density (GHD) functions as I intend to become more familiar with these. But the results are different for each package.</p>
<p>How do the implementations differ?</p>
<pre><code># Comparing GHD fBasics and ghyp functions
set.seed(4242)
p... | g68226 | [
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<p>In the extreme case where all of the components of an $M$-variate observation are pairwise independent from each other, a multivariate normal distribution can be decomposed into the product of $M$ univariate normal distributions. For example, $$p \left( X_{1},X_{2},X_{3};[\mu_{1},\mu_{2},\mu_{3}]^{T},\left[\begin{ar... | g68227 | [
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<p>Short question: What happens to the beta-binomial distribution, when n increases to infinity? Is there a count distribution arising like it's for the classical binomial distribution? </p> | g48979 | [
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<p>You may have heard about the recent enterohaemorrhagic <em>E. coli</em>
(<a href="http://en.wikipedia.org/wiki/EHEC" rel="nofollow">EHEC</a>)
<a href="http://en.wikipedia.org/wiki/2011_E._coli_O104%3aH4_outbreak" rel="nofollow">outbreak in Germany</a>.<br>
What questions would a statistician ask about EHEC analysis... | g17821 | [
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<pre><code>R version 3.1.1 (2014-07-10) -- "Sock it to Me"
> bl <- c(140, 138, 150, 148, 135)
> fu <- c(138, 136, 148, 146, 133)
> t.test(fu, bl, alternative = "two.sided", paired = TRUE)
Error in t.test.default(fu, bl, alternative = "two.sided", paired = TRUE) :
data are essentially constant
</code></p... | g68228 | [
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<p>I have a dataset with 4025 participants across two time points. I have scored them on a three-point categorical variable (<code>Unlikely, Possible, Probable</code>) at each time point. I would like to visualize the various patterns of change (e.g. going from <code>Unlikely</code> at T1 to <code>Possible</code> at T2... | g68229 | [
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<p>As far as I know, the variance inflation factor is not computed with pseudo-$R^{2}$ or generalized $R^{2}$ in binary outcome models (e.g. logistic regression).</p>
<p>Are there other measures of multi-colinearity than VIF appropriate to such models?</p>
<p>Why ought or ought not we think about multi-colinearity in... | g28135 | [
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<p>I'm using the DLM package to estimate a multivariate time series, I wanna check the out of sample forecasting, by estimating the residuals for 1, 6, 12 months ahead forecast? How can I calculate the 6 and 12 months ahead forcast like the kalman filter does for 1 month ahead forecast?</p>
<p>Thanks</p>
<p>Since thi... | g28137 | [
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<p>For a Bayesian logistic regression problem, I have created a posterior predictive distribution. I sample from the predictive distribution and receive thousands of samples of (0,1) for each observation I have. Visualizing the goodness-of-fit is less than interesting, for example: </p>
<p><img src="http://i.stack.img... | g2871 | [
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... |
<p>I am trying to determine colors to best grab a web-users attention.</p>
<p>I have a simple system which randomly chooses one of 4 foreground colors, and one of 6 background colors.</p>
<p>I then save the stats in a table like this:</p>
<pre><code>fore_color back_color shown clicked
---------- ------... | g48984 | [
0.020519115030765533,
0.055404823273420334,
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0.0058185262605547905,
0.03286457806825638,
0.002101090969517827,
0.... |
<p>$X$ is a positive variable with known support (assume discrete support, if that simplifies solution).</p>
<p>$Y$ is another variable with the same support.</p>
<p>$X$ and $Y$ are independent.</p>
<p>$Z$ is equal to $X$ if $X < Y$, and equal to $0$ otherwise.</p>
<p>$Y$ and $Z$ are observed, $X$ is not. How to... | g68230 | [
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0.02440912276506424,
-0.020231403410434723... |
<p>I'm doing this book "Modeling and reasoning with Bayesian Networks" and I have this problem: </p>
<pre><code>ConsidertheDAGinFigure4.14:
(a) List the Markovian assumptions asserted by the DAG.
(b) Express Pr(a, b, c, d, e, f, g, h) in terms of network parameters.
(c) Compute Pr(A = 0, B = 0) and Pr(E = 1 | A = 1... | g28140 | [
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0.... |
<p>Just a small introduction to the setting: I have traffic that is generated using several layers. Layer 3 consists of the basic packets, while Layer 2 is a more high level grouping of packets, and Layer 1 is even higher.
I have now this list of interarrival times between packets/groups for each layer. These interrarr... | g28142 | [
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<p>I'm looking to compare effects $ \delta = \frac{\mu_T - \mu_C}{\sigma}$ for two studies, compared with the same control group. In order to find the covariance of effects for treatment A and treatment B, I need to find</p>
<p>$$
E \left[ \left( \frac{\bar{A} - \bar{C}}{s} \right) \left( \frac{\bar{B} - \bar{C}}{s} \... | g68231 | [
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0.0... |
<p>I have a panel data set organized around 35 provincial units, with 110 binary "positive" outcomes in the dependent variable. This is for about 2600 observations in that data set. I have a couple questions. 1) Would it even be reasonable to run a logit at the national level, combining each province count? 2) Is i... | g68232 | [
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<p>I have a multifactor model (with 7 factors currently) and 754018 observations. In order to check for multicollinearity issues as the model grows I wrote an R script to compute a correlation matrix from the factors (so with 7 factors it's a 7x7 matrix). I then apply the function:</p>
<p>$$\frac{r}{(1-r^2) / (N-2)}$$... | g28144 | [
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0... |
<p>Could someone explain me which is the null hypothesis of the energy test of multivariate normality (R package <code>energy</code>)? By using this test I obtained a very different p-value from that I obtained with <code>mshapiro.test</code>.</p> | g48990 | [
0.10218068212270737,
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-... |
<p>I have to do some studies on time series, which involve computing the covariance matrix. However, my time series span on different time intervals and their intersection is too short to provide me a good estimator.
I guess I have to remove some time series but I don't know how to select the ones to keep. </p>
<p>I ... | g68233 | [
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0.... |
<p>I'm using the Kevin Murphy's HMM library in MATLAB(<a href="http://www.cs.ubc.ca/~murphyk/Software/HMM/hmm.html" rel="nofollow">http://www.cs.ubc.ca/~murphyk/Software/HMM/hmm.html</a>)</p>
<p>There is a section called 'How to use the toolbox'. There is this example for GMM ouputs:</p>
<pre><code>Let us generate ne... | g11535 | [
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0.024559902027249336,
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-0.020963134244084358,
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0.00977313332259655,
0.00... |
<p>In the one-dimensional case it is easy to obtain random numbers that are not too far away from the mean by checking if they are within one or two standard deviations. Is there some similar way to obtain random numbers that are not to far away from the mean vector of a multivariate normal distribution?</p>
<p>Thank ... | g68234 | [
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-0.04811811447143555,
0.03819436579942703,
0.0018261147197335958,
-0.008306317962706089,
... |
<p>Suppose I carry out the <a href="http://robjhyndman.com/hyndsight/crossvalidation/" rel="nofollow">following exercise</a> with my trusty statistics software:</p>
<ul>
<li>Fit some time-series model to the data $y_1,\dots,y_t$ and calculate $\hat{y}_{t+1}$, the forecast of the next observation, and the error $e_{... | g68235 | [
0.0011943404097110033,
-0.050873760133981705,
-0.008771319873631,
0.015820708125829697,
-0.017349744215607643,
0.009953686036169529,
0.1078021228313446,
0.00855791661888361,
-0.051723822951316833,
-0.020145542919635773,
0.005218542646616697,
0.005586613435298204,
0.08248565346002579,
0.023... |
<p>Say one has the fatality and survivor rates of a pathogen in terms of geographical location (e.g., the latest data on the <a href="http://www.cdc.gov/coronavirus/mers/overview.html" rel="nofollow">MERS-CoV</a>).</p>
<pre><code>France 2 (1)
Italy 3 (0)
Jordan ... | g68236 | [
0.02129502035677433,
-0.028185740113258362,
0.001005052006803453,
-0.012354983016848564,
-0.042106594890356064,
-0.005115409381687641,
0.02316373772919178,
0.0644167959690094,
0.019921747967600822,
-0.012715657241642475,
0.06086814031004906,
-0.007891103625297546,
0.082396000623703,
-0.004... |
<h2>Intro</h2>
<p>This is my first time posting on here, so please, if anything doesn't seem technically correct, either in the formatting, or the use of correct definitions, I'm interested to know what should've been used instead.</p>
<p>Onwards.</p>
<p>I've recently been taking part of the <a href="https://www.cou... | g28156 | [
0.019032182171940804,
-0.03456117585301399,
0.0033132329117506742,
-0.06822188943624496,
0.018599433824419975,
0.019622571766376495,
0.04004876688122749,
0.023367350921034813,
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-0.06362423300743103,
0.023978913202881813,
0.04958206042647362,
0.0636993870139122,
-0.042... |
<p>If there is more appropriate terminology to better phrase my question, please edit. </p>
<p>Imagine I have a 3 sided die: two faces marked 0, one face marked 2</p>
<p>Whenever a two is rolled, two more rolls are to occur. How do I determine the average number of rolls that will occur?</p>
<p>I tried figuring this... | g28157 | [
-0.0033564085606485605,
0.03547150641679764,
-0.019540822133421898,
-0.07123605906963348,
0.0189242884516716,
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-0.001962153473868966,
-0.024622328579425812,
0.0016812747344374657,
0.06591681391000748,
0.... |
<p>I am reading a research paper about the relationship between service quality and consumer behavior. One hypothesis is: customers experiencing no service problems have the strongest levels of favorable behaviors and the smallest levels of unfavorable behaviors.
ANOVA was operated, results are:</p>
<p><img src="http:... | g68237 | [
-0.003288142615929246,
0.03218729794025421,
-0.009896152652800083,
0.026505526155233383,
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0.01408932264894247,
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0.02244180254638195,
0.0026059234514832497,
-0.007839060388505459,
0.02442765235900879,
-0.009057281538844109,
... |
<p>I am looking for a way to estimate the variance of a summed sub-set based on the variance of those sums.</p>
<pre><code>Si = sum( Ai )
S = { S0...Sn }
V = variance( S )
</code></pre>
<p>That is, each sample value <code>Si</code> is actually the sum of a set <code>Ai</code>. <code>V</code> is then the normal varian... | g28159 | [
-0.017408372834324837,
-0.004784000106155872,
-0.016017889603972435,
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0.045450057834386826,
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0... |
<p>I have around 300 features, i need to choose features for one class svm. can some one tell me the ideal algorithm for this use case. I know about that for feature selection regularised random trees/SVM/correlation can be used. But I am not sure which specific algorithm would be useful for one class svm. Please guide... | g68238 | [
0.007425164803862572,
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0.02380477637052536,
0.030712099745869637,
0.0005168385105207562,
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0.08601886034011841,
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-0.0053648450411856174,
-0.0017110082553699613,
0.03637155890464783,
0.043588243424892426,
... |
<p>I've seen references to learning Bayesian probability theory in R, and I was wondering if there is more like this, perhaps specifically in Python? Geared towards learning Bayesian probability theory, inference, maximum likelihood estimation, graphical models and the sort?</p> | g68239 | [
0.014736083336174488,
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0.03252663090825081,
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-0.0281464122235775,
0.030082976445555687,
0.019908875226974487,
0.09494020789861679,
0.03941... |
<p>I am trying to do a multivariable logistic regression and using a normal binomial logistic regression, using binomial variable <code>X</code> (coded <code>0</code>/<code>1</code>) and <code>Y</code> (4 sub-categories). Unfortunately, the reference category was shown to be not significant. Should I then reject the nu... | g68240 | [
0.020847978070378304,
-0.006813569460064173,
0.014626110903918743,
-0.015456859022378922,
0.017042120918631554,
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0.019914941862225533,
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-0.02145640179514885,
0.04553188383579254,
0.02980554662644863,
0.01698501594364643,
0.0... |
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