question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I wonder how I can modify the K-means algorithm so that the cluster volumes are not equal to each other. The K-means objective is to minimize within cluster sum of squares $\sum_{i=1}^{p} {\parallel \mathit{X}_i-\mathit{L}_{\mathit{Z}_i} \parallel}_2^2$, and this objective assumes that all cluster variances are the ... | g67213 | [
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<p>I have a bayesian network with conditional probabilities as given by the diagram and I have converted it to factor graph. I just sort of read about factor graphs. Can someone be kind enough to let me know if I have done the factor graph representation correctly? I really appreciate your help.</p>
<p><img src="http:... | g67214 | [
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<p>I got a warning message when I was trying to do anova for two nlme::gls objects. Here is an example:</p>
<pre><code>require(nlme)
set.seed(123)
y<-rnorm(100,10,2)
x1<-rnorm(100)
x2<-sample(1:5,100,T)
x3<-rt(100,20)
x4<-rbinom(100,1,0.3)
fit1<-gls(y~x1+x2+x3+x4,correlation=corAR1(form=~1|x4))
fit2&... | g67215 | [
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<p>(Note: I did look at similarly worded questions and none seem to answer this one.)</p>
<p>Given this scenario: People can rate 0 or more items on a scale of 0-X. I am trying to find the Wilson score interval (WSI) for each item with at least 1 rating. Does the WSI apply to such situations? If so, can Anyone point M... | g67216 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/4220/probability-distribution-value-exceeding-1-is-ok">Probability distribution value exceeding 1 is OK?</a> </p>
</blockquote>
<p>I'm comparing results given by <a href="http://stackoverflow.com/questions... | g49345 | [
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<p>The linear SVM in textbook takes form of maximizing</p>
<p>$L_D = \sum_i{a_i} - \frac{1}{2}\sum_{i,j}{a_ia_jy_iy_jx_i^Tx_j}$</p>
<p>over $a_i$ where $a_i \geq 0$ and $\sum_i{a_iy_i} = 0$</p>
<p>Since $w = \sum_i{a_iy_ix_i}$, the classifier will take the form $\text{Sgn}(wx - b)$.</p>
<p>Thus, it seems to solve l... | g47239 | [
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<p>I'm trying to use Brewer's method to sample 12 units out of a population of 73.</p>
<p>I read on Brewer and Hanif's "Sampling with unequal probabilities" that the probability must be proportional to $$\frac{P_i (1 - P_i)}{(1-rP_i)}$$. </p>
<p>I know that for $n = 2$ the first unit is selected with probability $$\... | g67217 | [
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<p>I am hoping to compare the sample mean of an experimental group to the sample mean of three control groups. </p>
<p>Here is some context for the study:</p>
<p>The experimental group consists of ~60 persons with a particular criminal record who were afforded various rehabilitative services. For each person, I have ... | g67218 | [
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<p>I am running an ordinal logistic regression in R and running into trouble when I include dummy variables. My model works great with my first set of predictors. Next I want to add dummy variables for each of the years represented in my dataset. </p>
<p>I created the dummy variables with <code>car:recode</code> in... | g47241 | [
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<p>I am trying to plot a histogram of my data, and I seem to be a little confused here. I am using matplotlib in Python. Here is the code from their website:</p>
<pre><code>mu = 100 #mean
sigma = 15 #std deviation
x = mu + sigma * np.random.randn(10000)
# the histogram of the data
n, bins, patches = plt.hist(x, num_b... | g67219 | [
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<p>I have a follow up question to MånsT's reply to the "<a href="http://stats.stackexchange.com/a/29784/3277">When should you center your data & when should you standardize</a>"-question. ( I cannot leave a comment as I am below the magic "50 reputation".) He says that </p>
<blockquote>
<p>In addition to the rem... | g67220 | [
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<p>I am trying to manage a meta-regression in SPSS17 using the effect size as the dependent variable. I want to explore if my independent variables affects the effect size. Some small practical questions:</p>
<ol>
<li><p>What is the minimum number of studies necessary for a meta-regression?</p>
<ul>
<li>Some people s... | g26677 | [
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<p>I have data about how many unique users do a certain thing for each day of a month. I can average it, and i would like to display the variation in a intuitive format (such as % of something).</p>
<p>Is there a standard way of doing this? </p>
<p>I've found standard error, which is $\frac{\sigma}{\sqrt{n}}$, which... | g67221 | [
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<p>I am interested in fitting an ARDL model that has 4 lags for each explanatory variable.
However, when I fitting the model in R. R says that coefficients are not defined because of singularities. Is this because I have too many lags ? Further, how should I choose the appropriate lag ?</p>
<p>(all variables are stat... | g67222 | [
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<p>I am using simulations to make a calculation. I generate many random numbers from a distribution for each input and then I take the mean and standard deviation of the outputs.</p>
<p>I noticed that the mean output from the simulations is always slightly higher than the result would be had I not used the distributio... | g67223 | [
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<p>I recently wrote a program that graphed data points so that a user could scroll through them and find "interesting" parts of the data.</p>
<p>Now I am looking at ways to make it even simpler by making a table of values deemed to be interesting. These are usually either the value switching to a new value, or spiking... | g47247 | [
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<p>I'm using <code>R2WinBUGS</code> to process several datasets in WinBUGS in "batch mode". Occasionally traps occur, mainly due to bad parameters (I guess), and I managed to avoid the whole R script to stop using <code>try</code>, and to retry automatically. Yet, when this happens, I have to manually close WinBUGS in ... | g67224 | [
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<p>I have two random variables $X$ and $Y$ which follows Normal distribution , whose pdf's are given by</p>
<p>$f(x)= \frac{1}{2 \sqrt{2 \pi} \sigma}[e^{\frac{-(x-1)^2}{2 \sigma^2}}+e^{\frac{-(x+1)^2}{2 \sigma^2}}]$ </p>
<p>$f(y)= \frac{1}{ \sqrt{2 \pi} \sqrt{1+ \sigma^2}}[e^{\frac{-x^2}{2(1+\sigma^2)}}]$</p>
<p>Bo... | g38110 | [
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<p>What is the relationship between propensity scores and sufficient statistics? I just came across the idea.</p> | g26680 | [
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<p>I am dealing with an existing algorithm where data is processed as follows:
We have a large sample of data taken every minute, this is grouped into 'buckets' of data for every hour.
(Each bucket contains a SUM(), MAX(), MIN() and the number of data points taken in the hour.)</p>
<p>Now, ideally there should have be... | g67225 | [
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<p>Let $X_1, \dots, X_n$ be independent exponential $(\theta)$ random variables. Suppose we are interested in testing $H_0: \theta = \theta_0 = 1$ versus $H_A: \theta = \theta_1>1$. Consider two tests with rejection regions:</p>
<p>Test 1: {$ (x_1, \dots, x_n) \in \mathbb{R}^n: \sum^n_{j=1} x_j \geq k_{\alpha}$},</... | g67226 | [
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<p>Suppose I have some baseline data $X_1$ and some post-baseline $X_2$. For example, the baseline data could be blood pressure. Some intervention is added (e.g. a blood pressure medication) and the post-baseline data is $X_2$ (blood pressure after medication). </p>
<blockquote>
<p><strong>Question.</strong> If I wa... | g42531 | [
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<p>In geostatistical context it is common practice that for simulations of a variable of interest (e.g., grade of concentrations of metal in rock samples) the <strong>number of simulations</strong> at least needs to be <strong>30</strong>. I would ask what <em>the criteria</em> is to choose a right trial number conside... | g31928 | [
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<p>I've produced a questionnaire with 3 parts, demographics, attitude questions, and then a final section on particular scenarios. I'm looking to analysis people's response to the scenarios - as in what factors affected their choices.</p>
<p>I've used Likert scales and also categorical - however, I've been using SPSS ... | g67227 | [
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<p>I’m interested in testing the impact of gender on personal selling. I have data on each salespeople’s amount of sales per customer for 22 months from Jan 2002 to Oct 2003 (amount of sales per customer $=y)$, each salespeople’s gender $(x_1)$, and a dummy variable (if the product is on sale, $x_2)$. Since gender is t... | g26685 | [
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<p>I have seen that copula transformation changes my sample space to the range of $[0 \; 1]^d$ where d is the number of dimensions. Can anyone explain me about copula transformation?</p> | g67228 | [
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<p>Short version: I need to compare two small (~10) groups of numbers, usual setup for a non-paired t-test, or Mann-Whitney. But -- the numbers come <em>each</em> with its own SE, and since the groups are small, this is presumably relevant. Question -- how do I take the individual SEs into account?</p>
<p>Longer versi... | g67229 | [
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<p>My understanding of the bayesian vs frequentist debate is that frequentist statistics:</p>
<ul>
<li>is (or claims to be) objective</li>
<li>or at least unbiased</li>
<li>so different researchers, using different assumptions can still get quantitatively comparable results</li>
</ul>
<p>while bayesian statistics</p>... | g5243 | [
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<p>logarithmic transformation which is used to stabilize the variance of the distribution of the sample variances , $S^2$.</p>
<p>$$S^2\sim^{asy} N(\sigma^2,\frac{2\sigma^4}{n-1})$$</p>
<p>Is that $$log S^2\sim N(log\sigma^2,\frac{2}{n})$$ or,</p>
<p>$$log S^2\sim N(log\sigma^2,\frac{2}{n-1})$$</p>
<p>I need onlin... | g26689 | [
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<p>I've computed a regression on panel data using the <code>xtreg</code> command in stata.
My coefficients on some of the independent variables (which are binary-variables) are out of the range of -1 +1, even though the dependent variable is log transformed. </p>
<p>I find this rather odd, since a result of -2,3 woul... | g26690 | [
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-0.058775655925273895,
-0.03134007006883621,
0.08284489065408707,
-0.00477304682135582,
-... |
<p>This is my first time here, so please let me know if I can clarify my question in any way (incl. formatting, tags, etc.). (And hopefully I can edit later!) I tried to find references, and tried to solve myself using induction, but failed at both.</p>
<p>I'm trying to simplify a distribution that seems to reduce t... | g67230 | [
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<p>What is best way to run OLS in R with linear inequality constraints, e.g.
$$y(x)= ax + b,$$ where $0<a<1$? </p> | g49772 | [
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<p>Could you guys give me a review on the challenges and common techniques in dealing with big data problem?</p>
<p>For example, what I know is that in when sample size is limited and dimension is high, the estimation of covariance would be an issue, what we did is to suppressing the big eigenvalues and increasing the... | g26691 | [
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<p>I've created a linear model in R: <code>mod = lm(train_y ~ train_x)</code>. I want to pass it a list of X's and get its predicted/estimateed/forecasted Y. I looked at <code>predict()</code>, but I think that is for something else, or I just don't know how to use it.</p>
<p>I'm guessing by taking the coefficients ... | g67231 | [
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<p>I'm trying to find statistical test (or procedure) which is able to <strong>discover patterns in spatial distribution of points.</strong> I sketch the problem by giving the example about position of bird territories and personality of birds.</p>
<p><strong>1.</strong>
Load this example data (<em>they are completely... | g794 | [
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<h1>Initial Problem</h1>
<p>I am working on a problem that determines the completion of projects. There are eight stages for the project to be in before completion, with the ninth stage being completion. There is a certain number of days between each project ranging from [0, $\infty$), i.e. the project can go from Sta... | g67232 | [
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<p>From <a href="http://en.wikipedia.org/wiki/Spearman%27s_rank_correlation_coefficient" rel="nofollow">wikipedia</a>, Spearman's rank correlation is calculated by converting variables $X_i$ and $Y_i$ into ranked variables $x_i$ and $y_i$, and then calculating Pearson's correlation between the ranked variables:</p>
<p... | g67233 | [
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<p>I want to compare 2 datasets. </p>
<p>I have a biological structure A with its atom coordinates which are a few thousands. I also have from these atom coordinates the coordinates over time of about 20 nanoseconds.
From this structure A I made about 70 simulations. After the simulation I calculated the distance bet... | g35636 | [
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<p>In the context of the classical linear regression model (with all standard assumptions), we know that when the error term is normally distributed, least squares is minimum variance among all linear unbiased estimators and we know the exact statistical distribution of the t statistics. </p>
<p>However, if the residu... | g26692 | [
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<p>On <a href="http://www.chsbs.cmich.edu/fattah/courses/empirical/multicollinearity.html" rel="nofollow">this page</a>, I read about multiple ways to deal with multicollinearity. I determined that the last method suggested may be best for my purposes. I copied it below:</p>
<blockquote>
<p>Treat the common variance... | g26693 | [
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<p>I have a unix shell data. Each session starts with <code><begin></code> and <code><end></code>. Between <code><begin></code> and <code><end></code>, the info contains users command in the shell session. From this data, I need to figure out how many users are on the system with probability.</p... | g26694 | [
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<p>Suppose I have a bivariate responses with significant correlation. I am trying to compare the two ways to model these outcomes. One way is to model the difference between the two outcomes:
$$(y_{i2}-y_{i1}=\beta_0+X'\beta)$$
Another way is to use <code>gls</code> or <code>gee</code> to model them:
$$(y_{ij}=\beta_0... | g67234 | [
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<p>Let the first document involve the words $\{x_1,x_2,\ldots,x_n\}$ and the second one be composed of $\{y_1,y_2,\ldots,y_m\}$ where $n$ is not necessarily equal to $m$. I have a similarity measure that works for elements of the sets; $s(x_i,y_j)$ for all $i$ and $j$. This similarity may not be symmetric, that is, $s(... | g67235 | [
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0.0... |
<p>I know that McElroy R^2 is a measure of goodness of fit for Seemingly Unrelated Regressions (SUR models), but how can one judge that the estimated equations are well fit by using the McElroy R^2?</p> | g17369 | [
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<p>Are there any R scripts that accompany the book of <code>Analysis of Financial Time Series, Third Edition
</code> I went to the book's webpage, and just found the data set.</p> | g67236 | [
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<p>$TX$ is variable that indicates treatment status ($TX=1$ if the patient gets the new treatment, and $0$ otherwise, and $UC = 1 - TX$ indicates they got the standard treatment). </p>
<p>Of $N$ patients, $n_{UC}$ get usual care and $n_{TX}$ get new treatment.</p>
<p>If $n_{UC} + n_{TX} = N$, show that $\sum_i(TX_i-\... | g67237 | [
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... |
<p>I have a project to improve user experience in our software by gathering data on their actions while using the software and comparing that to preferences they made when initializing the software. The idea is that if they say they like Coke but they keep drinking Pepsi, we would (1) ask "Are you sure you like Coke, n... | g67238 | [
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0.0652... |
<p>I'm trying to derive a kernel-ized $l_1$ penalty for logistic regression. I have been looking at the slides <a href="http://www.di.ens.fr/~fbach/mlss08_fbach.pdf" rel="nofollow">Learning with Sparsity Inducing Norms</a> along with the slides on <a href="http://www.stanford.edu/~hastie/TALKS/enet_talk.pdf" rel="nofol... | g67239 | [
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<p>I am looking for deep learning libraries that have very good tutorials or examples, since I would like to learn by examples or doing tutorials even if these are not the best deep learning libraries. If they also run on GPUs much better.</p> | g47276 | [
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<p>i have a histogram with the y-axis showing the proportion in percentage. That makes sense to me but now i have read that histograms can be normalized with the result that the area of the rectangles is 1.</p>
<p>Can someone explain me the idea,reason behind this? Many thanks!</p> | g6894 | [
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0.006... |
<p>I am wondering if there is a table or some reference that explains the strength of the beta coefficient.</p> | g67240 | [
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0.015... |
<p>The issue of unit roots and what $ I(1) $ variables do to a regression estimation is covered clearly online. However, it is of course possible to have order of integration greater than 1. What does it actually mean to say a time series is $ I(n) $ where $n>1$ ? What would a series like this look like? Are there a... | g67241 | [
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<p>Something nice and topical. I just read these two items on the news:</p>
<ul>
<li><p>Obama is in the lead by 50.4% to 48%, with 61% of votes counted. (Ohio)</p></li>
<li><p>With 86% of the vote counted, Virginia is still sitting on a knife edge. Romney is hanging on to a lead of 49.9%, but Obama is snapping at his ... | g67242 | [
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<p>I know this is a dumb question, but I can not find an answer (I guess everyone else knows this). I want to verify: </p>
<p>When I do k-fold cross validation of a decision tree, the software produces a confusion matrix for the test data. Is each instance assigned the most frequent class in the cross validation resu... | g67243 | [
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<p>I am roughly running an OLS regression of prices and the number of network providers in cities in the UK. Let $P$ stand for prices and $net$ stand for the number of network providers. The frequency of $net$ is: </p>
<pre><code>net frequency
0 100
1 140
2 100
3 40
4 10
5 ... | g48713 | [
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0.01646760106086731,
0.0497339703142643,
0.03... |
<p>I would like to know if anyone could recommend a book that deals more with the practical issues around conducting a meta-analysis?</p>
<p>Thanking you in advance</p>
<p>Andrew Vitiello </p> | g49773 | [
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0.0613776296377182,
0.0... |
<p>Permutation tests are significance tests based on permutation resamples drawn at random from the original data. Permutation resamples are drawn without replacement, in contrast to bootstrap samples, which are drawn with replacement. Here is <a href="http://stackoverflow.com/questions/2449226/randomized-experiments-i... | g47292 | [
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<p>How should I elicit prior distributions from experts when fitting a Bayesian model?</p> | g38203 | [
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0.033... |
<p>The dependent variables in a MANOVA should not be "too strongly correlated." But how strong a correlation is too strong? It would be interesting to get people's opinions on this issue. For instance, would you proceed with MANOVA in the following situations?</p>
<p>a) Y1 and Y2 are correlated with r=0.3 and p<0.... | g47293 | [
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0.0... |
<p>Suppose we have a regression model that measures college Grade Point Averages. The variables that we are using are <code>hsize</code> (the size of the graduating class in hundreds), <code>hsize squared</code>, <code>sat</code> (SAT Scores), <code>female</code>, and <code>athlete</code>.</p>
<p>After estimating for ... | g49359 | [
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0.0079... |
<p>A colleague in applied statistics sent me this:</p>
<blockquote>
<p>"I was wondering if you know any way
to find out the true dimension of the
domain of a function. For example, a
circle is a one dimensional function
in a two dimensional space. If I do
not know how to draw, is there a
statistic th... | g26707 | [
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0.07988167554140091,
-... |
<p>How to find joint sufficient statistic for a pair of unknown parameters from a bivariate random sample? Also, what exactly does nontrivial mean in this context? Please elaborate and be simple in your illustration, as much as you can.</p> | g67244 | [
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-0.022453658282756805,
-0.021852532401680946,
0.021198930218815804,
-0.02177724987268448,
0.02978556975722313,
-0.03827999159693718,
-0.017674345523118973,
-0.026905376464128494,
... |
<p><a href="http://www.cs.rug.nl/svcg/uploads/Publications/density.pdf" rel="nofollow">Ferdosi et al</a> define six artificial datasets to test density estimation methods. Part of the fourth dataset is defined as: </p>
<p>$$ Uniform(x,y) = [0,100], Gaussian(z) = [M = 50, var = 5] $$</p>
<p>Where $M$ is defined as the... | g26710 | [
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0.06522294133901596,
-... |
<p>I would like to ask you (statistics experts) if the following approach is kosher or a nonsense.</p>
<h3>Problem</h3>
<p>My EM based detection algorithm ends up (for some data) with a result that looks like attached picture. With second peak I am satisfied, but first one is only a noise. </p>
<p><img src="http://i... | g67245 | [
0.028744827955961227,
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0.014625618234276772,
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0.07308343797922134,
0.02... |
<p>There is a random vector $X=(X_1,\ldots,X_p)$, with $p$ large, $E[X]=0$ and $V[X_j]=1\ \forall \, j=1,\ldots,p$, but the correlations are different from zero. We cannot assume multivariate normality for $X$ (the marginal distributions are slightly skewed and heavy-tailed, as common in financial data).</p>
<p>Say we... | g67246 | [
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0.01595706306397915,
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0.031606391072273254,
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-0.024758189916610718,
0.04166824370622635,
0.017914222553372383,
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0.00... |
<p>I'm trying to understand how <a href="http://en.wikipedia.org/wiki/Non-negative_matrix_factorization" rel="nofollow">NMF</a> derived, and I got the basic idea of NMF,
that is, it tries to appoximate original matrix $V$ with $WH$, where $V$ are non-negative, and $W,H$ are constrained to be non-negative.</p>
<p><stro... | g67247 | [
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0.04163841903209686,
0.05... |
<p>I searched a method to determine the accuracy of a linear regression model. I found that I should calculate r-squared. Is this the only method or are there other methods?</p> | g67248 | [
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<p>Suppose the true model is $y = 2x + \text{error}$, where $\text{error}$ is normally distributed with variance 1 and mean 0. See the R code below. Variance for any residual from the fitted model (under OLS) is given by $\text{Var}(\text{error}) \times (1 - \text{hatvalue})$. Ex: var(residual) for the first observatio... | g67249 | [
0.03028802014887333,
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0.0189561378210783,
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0.0... |
<p>I get a negative value for the Hausman test for the independence of irrelevant alternatives (IIA) assumption. Now I find contradicting conclusions in the literature: some people say that I should take the absolute value, others say that the value should be rounded to $0$. What should I do?</p> | g67250 | [
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0.... |
<p><a href="http://cs.stanford.edu/people/ang/papers/nips07-sparsedeepbeliefnetworkv2.pdf" rel="nofollow">Sparse RBM are described in this paper</a></p>
<p>Gaussian-Bernoulli RBMs are describe (kinda poorly) in <a href="http://papers.nips.cc/paper/3048-greedy-layer-wise-training-of-deep-networks.pdf" rel="nofollow">th... | g67251 | [
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-0... |
<p>I'm new to ARIMA analysis and I'm trying to understand how fitted ARIMA model can be used to forecast new time series, given starting point only. Should the model be refitted or the estimated parameters are sufficient to produce forecasts? Thanks</p> | g67252 | [
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<p>After training using random forests on the iris dataset, I get an OOB error and a confusion matrix. </p>
<pre><code>data(iris)
(model <- randomForest(Species~., iris, ntree=500,importance=T,do.trace = 100) )
model$oob.times
</code></pre>
<p>The help mentions that the confusion matrix is based off the OOB data. ... | g67253 | [
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<p>Apologies if this is a bit of a simple question, but I haven't been able to find any answer to this over the past week and it's driving me crazy.</p>
<p>Background Info: I have a dataset that tracks the weight of 5 individuals over 5 years. Each year, I have a distribution for the weight of individuals in the group... | g26716 | [
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<p>I have monthly sales data for 50,000 companies. Unfortunately, I have very limited statistics training. </p>
<p>I suspect/hope that by some measure of growth these companies would fit into a standard normal distribution, but I can't figure out what that measure would be. By default we measure growth as a ratio, e.g... | g67254 | [
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<p>I am using the 'topicmodels' package in R. I tested the posteriori probability for
newdata over jss_LDA result by this code : </p>
<pre><code>post <- posterior(jss_LDA, newdata = dtmNew)
</code></pre>
<p>For each words i have the probability over all topics. What is the signifiance of each value probability in... | g696 | [
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<p>I have box-office collection data on a number of movies. I also have the production budget, director name, lead actor, actress, language and other meta data related to the movie. I want to know which factors determine the box office collection. If a certain factor (say the director) is correlated with the collection... | g67255 | [
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<p>In my job role I often work with other people's datasets, non-experts bring me clinical data and I help them to summarise it and perform statistical tests.</p>
<p>The problem I am having is that the datasets I am brought are almost always riddled with typos, inconsistencies, and all sorts of other problems. I am in... | g49631 | [
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<h3>Context</h3>
<p>This came up recently in a consulting context. A researcher was performing repeated measures t-tests based on experimental data.
Some of the analyses involved comparing one condition with another. Other analyses involved performing contrasts comparing one or more conditions with one or more other c... | g9728 | [
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<p>I'm using latent semantic indexing to find similarities between documents (<a href="http://stats.stackexchange.com/q/11102/1977">thanks, JMS!</a>)</p>
<p>After dimension reduction, I've tried k-means clustering to group the documents into clusters, which works very well. But I'd like to go a bit further, and visua... | g67256 | [
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<p>I am working on understanding various document ranking algorithms like (TF-IDF, LSI, language models, etc) by actually implementing them. I want to understand LDA and using various resources to understand the algorithm. What I don't understand is how we come up with the latent (hidden) variables/topics. Can someone ... | g47319 | [
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<p>I would appreciate any help you could give me
I have ordinal data which I want to standardise in order to compare averages and data spread between variables. I need to standardise since the variables have different scales (one is out of 7, the other out of 15). I have transformed the original values into percentage... | g67257 | [
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... |
<p>I am studying stock price.</p>
<p>I first define that the ln(price) has an obvious unit root of 1 lag.</p>
<p>I was wondering if someone could explain me how to proceed to construct a correct ARMA model...?</p>
<p>Thanks is advance.</p> | g67258 | [
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<p>I have a classifier that I'm doing cross-validation on, along with a hundred or so features that I'm doing forward selection on to find optimal combinations of features. I also compare this against running the same experiments with PCA, where I take the potential features, apply SVD, transform the original signals ... | g67259 | [
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<p>I am using AICc for small sample sizes to compare 8 <em>a priori</em> models (including null model). I fitted my models using a GLMM due to the nested nature of my data and defined the family as 'poisson' based on a visual inspection of the error structure from my residual vs fitted values plot.</p>
<p>After runnin... | g67260 | [
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... |
<p>I've read that using log scales when charting/graphing is appropriate in certain circumstances, like the y-axis in a time series chart. However, I've not been able to find a definitive explanation as to why that's the case, or when else it would be appropriate.
Please keep in mind, I'm not a statistician so I may b... | g49875 | [
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<p>I have a series of data points, and I want to see how much evidence there is that the points are getting bigger over time. The data themselves are counts, but for various reasons I don't want to build a model of this as a Poisson process with potentially changing lambda. I'd like to only look at order statistics. </... | g67261 | [
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<p>Please suggest a data entry tool (if one exists) for a single large sparse table.</p>
<p>Something like...</p>
<p>row x, checkbox list of 300 columns, check 5 that pertain, enter data for those 5.</p>
<p>row x+1, same checkbox, check different 14 that pertain, enter data for those 14.</p>
<p>row x+2, checkbox do... | g67262 | [
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<p>I was assigned to demonstrate the Central Limit Theorem (CLT) in R in my statistics class. I already made some progress with simulation using simple.sim in R. I want to prepare 3 examples of the CLT with continuous distributions (<em>rnorm</em>, <em>rt</em> and <em>rf</em>) and 3 examples with discrete distributions... | g4949 | [
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<p>I have written a program which generates random data. If the program is working correctly, that data should follow a specific, known probability distribution. I would like to run the program, do some calculations on the result, and come up with a p-value.</p>
<p>Before anybody else says it: I understand that hypoth... | g49733 | [
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<p>I have two data sets from different collections. The second data set is smaller. They were both analyzed with the same methods in order to derive feature sets of 10-30 features each. Each feature set was produced the same way for both data sets. </p>
<p>Then, I run many Logistic Regressions to fit both data sets wi... | g26733 | [
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<p>Are random effect models same as Bayesian version of fixed effect models, in the sense that the parameters or coefficients are random variables? </p>
<p>For example, is the <a href="http://en.wikipedia.org/wiki/Bayesian_linear_regression" rel="nofollow">Bayesian linear regression</a> model viewed as a random effect... | g67263 | [
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<p>Can some one show that a Bayesian ordinal logistic model with a proportional odds assumptions is the binary logistic regression with a different prior.
That is you are willing to take a multivariate normal prior for the regression parameters and an independent prior of the cutoffs, which can be truncated normal dis... | g796 | [
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... |
<p>I searched the entire web including this forum on some help on how to use the glmulti package in order to identify the "optimal" fixed part of a mixed model with a given random part. However, I could not find anything to solve my problem. PLEASE HELP!</p>
<p>I followed the introduction provided in the glmulti.pdf, ... | g26734 | [
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0.007641379255801439,
0.039113111793994904,
0.011599259451031685,
... |
<p>I have several subjects, for each subject I have two measure (pre and post treatment) of several parameters, I have calculated a multivariate similarity measure (Mahalanobis distance) between each dataset and a particular condition (target).</p>
<p>My similarity measure varies across time and I need to measure if t... | g67264 | [
0.011427225545048714,
-0.08039293438196182,
-0.009898154065012932,
0.00466924486681819,
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0.019146928563714027,
0.015891658142209053,
0.0188418198376894,
-0.005997704807668924,
-0.... |
<p>If I have a table with results (columns being different feature subsets and rows being different machine learning algorithms) how can I test whether or not some of the results (0-1 loss) is not significantly different from the best result? I have found a wide range of different statistical significance tests, but no... | g67265 | [
0.007171946577727795,
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0.049711644649505615,
0.0820927619934082,
... |
<p>Residuals and errors are related but not exchangeable. In <a href="https://en.wikipedia.org/wiki/Errors_and_residuals_in_statistics" rel="nofollow">Wikipedia</a> I read:</p>
<blockquote>
<p>In statistics and optimization, statistical errors and residuals are two closely related and easily confused measures of the... | g67266 | [
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0.... |
<p>Am I right in thinking that bootstrapping is just replicating your original data x amount of times?</p>
<p>So I have a series of $n=20$ sequences of varying length containing the letters ACGTE.
The probability of having C after to A is</p>
<p>$$
P(X_C=x_C|X_A=x_A),
$$</p>
<p>and which can be calculated from the s... | g67267 | [
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0.06470628827810287,
... |
<p>Using bootstrap I calculate p values of significance tests using two methods:</p>
<ol>
<li>resampling under the null hypothesis and counting the outcomes at least as extreme as the outcome coming from the original data</li>
<li>resampling under the alternative hypothesis and counting the outcomes at least as distan... | g67268 | [
0.016689889132976532,
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0.02368570864200592,
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0.0005780048668384552,
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0... |
<p>I would like to use a one sample t-test where accuracy is 50-50..</p>
<p>The data is rated on a three point likert scale of 1-performed task incorrectly, 2 - performed task with minor mistakes, 3-performed task accurately </p>
<p>I have calculated the mean and standard deviation of my data and that is fine, I am j... | g67269 | [
0.02243361435830593,
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0.01625175029039383,
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0.0025109255220741034,
-0... |
<p>This might be a silly question, but I could not find an equivalent one on CrossValidated.</p>
<p>I was wondering: if I transform my data in order to meet the assumption of homoscedasticity before running a two-way ANOVA, should I also use the transformed data to perform Tukey's post-hoc test and find out which trea... | g67270 | [
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0.006927461829036474,
0.0036914944648742676,
0.043819278478622437,
0.020053805783391,
-0.00... |
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