question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>My question is related to regression with missing covariate data. I have a sample of count data representing number of explosion incidents at each year. First $M$ observations were made by considering one criteria and the last $K$ were made considering two criteria. E.g. for the first $M$ years explosions were recor... | g37755 | [
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<p>The means for each category varies, but my hypothesis is that the second population has a higher mean within each category. The variance of each category is unknown.</p>
<p>The example I'm working with is a set of schools, all of which have been given new computers. The question is does, the introduction of compute... | g57891 | [
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<p>I wonder about the existence of "standard" statistical procedures for rounded (log)normal data. Indeed, in my work I often encounter rounded data which potentially cause some problems: "awful" qqplots, zeros for lognormal data... Do there exist in the literature some theoretical studies of usual statistical procedur... | g12713 | [
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<p>I have data on several companies where some are headed by a male CEO while others by a female CEO. As you can imagine, the jobs within these companies have different gender compositions. What I am trying to do is compare the gender distribution of employees across jobs for companies led by a male versus a female CEO... | g57892 | [
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<p>I'm running LMM models and could I ask if I can just report the model after comparing random intercept with random intercept and slope model without excluding nonsignificant factor?</p> | g12714 | [
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<p>Generally speaking I want to find out if the regression models I built are significantly different from each other. I have monthly energy consumption data (the independent variable) from a couple of houses and Heating Degree Days (<code>HDD</code>) covering a period of about 3 years. The data has been divided into g... | g12715 | [
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<p>I have collected data that represent stimulation levels in three different time points ($T_0$, $T_1$ and $T_2$) using three different stimulants ($S_1$, $S_2$ and $S_3$) and a control ($C$). I have tested all three stimulants with three different subjects ($J_1$, $J_2$ and $J_3$) and for each subject and stimulant/ ... | g12716 | [
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<p>Using the <code>predict()</code> command in R, I have been able to calculate estimates (<code>av2</code>) and se-intervals (upper, lower)for my data below. The calculated proportion (<code>av2</code>) is different from the observed proportion (<code>av1</code>) - so 1. I'm not sure why this is? When writing up the e... | g728 | [
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<p>I'm just starting to learn about missing data imputation methods, and I'm confused. In every introduction I've read, the author starts by describing listwise deletion and says that it's a bad idea because it reduces your N. They then explain methods you can use to fill in missing values so you can do your analysis w... | g57893 | [
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<p>I have a bunch of variables organized into 10 different levels of a grouping factor. I'm doing some ANCOVA on particular variables and also plotting the data using boxplots. I'd like to add 84% confidence intervals to all the groups (since non-overlapping 84% CIs indicate a significant difference at alpha .05 - at l... | g57894 | [
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<p>I am developing a search engine system based on the vector space model, and I am confused on what approach I should take to evaluate the system. </p>
<p>My case is this:</p>
<ol>
<li>I have a set of indexed documents in pairs (di,ti) stored in a database. And I can calculate the similarities between a query and th... | g57895 | [
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<p>What are good statistical journals with quick turnaround (fast review cycle), suitable for short notes in mathematical statistics and preferably with open access. An example is Statistics & Probability Letters, however, that journal only has sponsored open access.</p> | g12722 | [
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<p>Running a crude model using Bayesian inference, I get some results > 1 (ie, more than 100% "certain") for some combinations of "evidence". For instance, for one bit of evidence the conditional probability of the null hypothesis is 0.85 while the marginal probability is 0.77. If the prior probability is 0.9, the co... | g12724 | [
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<p>Consider the following experiment: a group of people is given a list of cities, and asked to mark the corresponding locations on an (otherwise unlabeled) map of the world. For each city, you will get a scattering of points roughly centered at the respective city. Some cities, say Istanbul, will exhibit less scatteri... | g41505 | [
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<p>Can anyone help me in re-scaling a five point likert scale into three categories using the mean scores. I have used a 5 point likert scale: </p>
<pre><code> (1) Not at all, (2) low, (3) moderate, (4) high and (5) very high
</code></pre>
<p>Now I want to categorize these into <code>Low</code>, <code>Moderate</co... | g57896 | [
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<p>What are the assumptions that need to be met when using hierarchical regression, and subsequently simple slopes analysis to test and probe interaction effects and how can I test for them in SPSS?</p>
<p>I have a continuous DV and IV, with a categorical moderator (3 categories).</p>
<p>Thanks in advance.</p> | g12726 | [
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<p>Why doesn't backpropagation work when you initialize all the weight the same value (say 0.5), but works fine when given random numbers? </p>
<p>Shouldn't the algorithm calculate the error and work from there, despite the fact that the weights are initially the same?</p> | g57897 | [
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<p>Is the following formula right if I want to measure the standard error of the median in case of a small sample with non normal distribution (I'm using python)? </p>
<pre><code> sigma=np.std(data)
n=len(data)
sigma_median=1.253*sigma/np.sqrt(n)
</code></pre> | g57898 | [
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<p>I have implemented PCA at Matlab. I just did dimensionality reduction (I don't use but I have class labels in my data set). My aim is to calculate overall accuracy and class-specific accuracy. I know that I can calculate overall (training data set and test data set) accuracy with PoV (Proportion of Variance Explaine... | g41510 | [
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<p>So I have data from a randomized blind trial of 1mg of nicotine gum on dual n-back working memory scores; I analyzed them as usual with a t-test and found a small increase in means but a large increase in standard deviations on a f-test! Strange. I also have data for each day on mood/productivity that day on a 1-5 s... | g57899 | [
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<p>I am trying to fit a problem with <code>regsubsets</code> with leaps in R. My problem is particularly strongly collinear, which is why I chose to use it in the first place. </p>
<p>The number of variables is about 200 and I have about 2 million independent observations. All the variables have a strong correlation s... | g57900 | [
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<p>I have a static panel data model with small T (T=5) that makes it impossible for me to use granger causality as it requires a long time span.</p>
<p>So my question: </p>
<ul>
<li>Is there any alternative solution to test for causation even in a small T context?</li>
</ul>
<p>Any hint will be highely appreciated!... | g57901 | [
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<p>I have read and seen a lot of Parallel coordinates plots. Can someone answer the following set of questions:</p>
<ol>
<li>What are parallel coordinates plots (PCP) in simple words, so that a layman can understand?</li>
<li>A mathematical explanation with some intuition if possible</li>
<li>When are PCP useful and w... | g41516 | [
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<p>Example code:</p>
<pre><code>(pc.cr <- princomp(USArrests)) # inappropriate
summary(pc.cr)
loadings(pc.cr) ## note that blank entries are small but not zero
</code></pre>
<p>I am getting different outputs from each, and I am not sure I understand what the difference is.</p>
<p>Here is the output:</p>
<pre><... | g57902 | [
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<p>I am trying to interpret some KPSS results for a large sample (n=1800 - <a href="http://data.is/TB2z5b" rel="nofollow">http://data.is/TB2z5b</a>). In general the <a href="http://en.wikipedia.org/wiki/KPSS_test" rel="nofollow">KPSS test</a> can be used for samples with time series with more than 100 observations? Is... | g57903 | [
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<p>I have created 2 decision trees, I just want to assure if I am making correct interpretation about it. Here is my first tree:
Note: Right click on image and select view image to view it clearly!</p>
<p><img src="http://i.stack.imgur.com/OhasY.jpg" alt="tree-1">
Here is interpretation:
Let us assume a value of iptt... | g46837 | [
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<p><strong>Short question:</strong> </p>
<p>I want to find out whether the means of 2 variables differ significantly. I know how large the dataset is (N~2000), but I only have the mean scores averaged over all participants. I do not have information about standard deviation. </p>
<p>Is there a test that can do that? ... | g12730 | [
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<p>I recently read a paper where the author says they used cointegration "with two degrees of freedom". What does degrees of freedom mean in this context?</p> | g57904 | [
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<p>I am facing a sentiment analysis task where I am using Naive Bayes to classify documents as Positive, Negative or Neutral. I have thought of using Information Gain as my filter for feature selection. Taking into account that I need to classify into 3 classes, would it be ok to use IG without further modifications (s... | g57905 | [
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<p>I got training set (time series) of size approximately 2 million precedents {x,y}. Each x is a vector of size 20 and each y is a binary vector of size 10 like {1,0,0,1,1,0,1,1,1,0}.
For a new input x I would like to obtain vector of probabilities {P(y_i = 1 | x)}.</p>
<p>So, what would you recommend?</p> | g12738 | [
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<p>I'm trying to calculate a pseudo-R2 for linear mixed models using Nagelkerke's method . </p>
<p>My understanding is that Nagelkerke's pseudo-R2=1-EXP[(-2/n)(l(B)-l(0))], where l(B) and l(0) are the maximized log-likelihoods for the fitted model of interest and the null (intercept only) model, respectively.</p>
<p>... | g12741 | [
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<p>I have a SPSS data file, which i am trying to reduce. However the data which belongs together is spread within multiple columns. I.e. I have one row per subject, but each subject has done multiple different conditions as well as procedures. The conditions are in columns <code>condition_1</code>, <code>condition_2</c... | g57906 | [
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<p>I am looking to fit some data with central multivariate t distributions. </p>
<p>I understand an ECME algorithm is the most promising way to do this. I wondered if anyone knew of any existing code for fitting t distributions with ECME that would get me started (in any language)?</p> | g57907 | [
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<p>I have a big dataset and I want to build a classification model (svm, rf, ann etc.). Then I split the original dataset into training set and test set. I build the model using training set. After it was done, I use the model to predict the test set. Here, the training set and test set should be similar in data struct... | g12743 | [
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<p>Let's say I'm running a model to look at questions asked on a form. My model looks like:</p>
<p>Price = B0 + B1(Gender) + B2(Age) + B3(Credit Type) + B4(Home) ...</p>
<p>I'm trying to calculate expected price for every possible scenario.</p>
<pre><code>So price for gender = 0, age = 18, home = 1, etc.
Price for g... | g57908 | [
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<p>With respect to the unsupervised learning (like clustering), are there any metrics to evaluate performance?</p> | g57909 | [
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<p>Suppose I have data that looks like this.</p>
<p><img src="http://i.stack.imgur.com/vxlIc.png" alt="enter image description here"></p>
<p>I want to quantify how well the "lower envelope" of the points are described by a monotonic function. The measure will be used to compare sets of points and should prefer sets w... | g57910 | [
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<p>Say that in a binary classification problem you have several negatives and only one positive. </p>
<p>What types of models are good to learn from this data, and predict the label for a new instance? Anything available in Python? From what I read <a href="http://stackoverflow.com/questions/17216640/one-shot-learning... | g57911 | [
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<p><strong>The experiment:</strong> Two groups of children perform tasks with three levels of difficulty at two different time points and brain activity is measured. All of the children perform all of the tasks and do so at both timepoints.</p>
<p><strong>Dependent variable:</strong> Brain Activity (BA)<br>
<strong>Re... | g57912 | [
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<p>I have paired data (GWAS case/control study) and I have heard using conditional logistic regression or generalized linear mixed models (GLMM) is appropriate. Which should I use in this case? Why would you use one over the other. More importantly can you guys point me towards resources for doing these methods in <cod... | g57913 | [
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<p>I have measurements $y_1$,...,$y_i$,...,$y_n$ taken from a set of replicates in a factorial designed experiment. </p>
<p>In order to use a linear regression I define my response $z_i = log(y_i + 1)$. The log is used in order to make the normality assumption hold and the model fit, and the + 1 is used since some $y_... | g57914 | [
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<h1>Problem:</h1>
<p><strong>The following code is to predict the last row's price
using all previous rows as a training set</strong>
** The prediction is very nice when the last row price smaller than 10, but becomes
unreasonable when the test price gets bigger.
** Same problem happens using SVM package</p>
<pre><... | g57915 | [
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<p>I am analyzing data with a binary outcome and a variety of continuous and categorical (including dichotomous) predictor variables. My approach is to perform a binary logistic regression and to treat any predictor with more than 20 unique values as continuous. Several arguments against categorization, especially well... | g37695 | [
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0.00224... |
<p>I need to calculate the following integral</p>
<p>$$\int_{\mu+c}^{\infty} y\cdot \frac{1}{\sigma\sqrt{2\pi}}e^{(y-\mu-w)^2/2\sigma^2}dy$$ </p>
<p>So essentially $y\sim N (\mu+w, \sigma^2)$ and im trying to calculate its expected value from $\mu+c$ to $\infty$</p>
<p>I know I will have to use integration by parts... | g57916 | [
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<p>I'm having trouble proving a N.N.D matrix has a N.N.D G-Inverse.</p>
<p>So far I have:</p>
<p>If we assume x = Az where x >= 0 and A is a nnd matrix. So if Y is a G-inverse than:</p>
<p>x = Az = YAz = Yx >= 0 .</p>
<p>Thus</p>
<p>Lx = LAz = Az >= 0 . So L is any G-inverse of A is also nnd. </p> | g57917 | [
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<p>I am trying to compare the results of two models.<br>
The first model looks at y with x as a fixed effect.
The second looks at the covariance between x and y.</p>
<p>Both models have repeated measures for x and y, so individual is included as a random effect. I am running the models in MCMCglmm. I am running them... | g57918 | [
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0.002880... |
<p>I came across a formula presented in a financial context, and have been trying unsuccessfully to try a work out what it means.</p>
<p>$SL = 2 * 100 * \sqrt{V_L + (\alpha + \beta)^k \sigma^2_{n - V_L}}$.</p>
<p>I have been scouring the net and can't see anything that comes close, so any help would be appreciated. ... | g57919 | [
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0.020... |
<p>Sorry if this type of question is not kosher. I'm new around here, so please forgive me.</p>
<p>Anyway, I have a dataset that describes the probability that users will like certain articles from my corpus <em>(with 5 articles chosen randomly and graphed below. Along the x axis are individual users, and along the y-... | g57920 | [
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<p>Let's say I'm fitting data for example to ARMA(1,1)-model:</p>
<p>$x_t = \phi x_{t-1} + \epsilon_t + \theta \epsilon_{t-1}$.</p>
<p>Now I estimate the parameters $\phi$ and $\theta$ and solve some values for them, e.g. </p>
<p>$x_t = 0.7 x_{t-1} + \epsilon_t + 0.8 \epsilon_{t-1}$ (I just made the numbers up)</p>
... | g57921 | [
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0.03727472573518753,
0.0691174641251564,
0... |
<p>For some reason, I can't seem to find the formula for prediction intervals in ridge regression anywhere. I know that the coefficient estimates are biased, but are the predictions (dependent variable) biased as well?</p> | g15028 | [
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... |
<p>Could we say time series forecasting is a part of data-mining or it's just a data-mining tool?</p> | g40612 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/8318/interpretation-of-log-transformed-predictors-in-logistic-regression">Interpretation of log transformed predictors in logistic regression</a><br>
<a href="http://stats.stackexchange.com/questions/12715/s... | g49518 | [
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0.021579788997769356,
-0.... |
<p>I am taken by the idea of James-Stein shrinkage (i.e. that a nonlinear function of a single observation of a vector of possibly independent normals can be a better estimator of the means of the random variables, where 'better' is measured by squared error). However, I have never seen it in applied work. Clearly I am... | g122 | [
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<p>What is the difference between having something statistically significant (such as a difference between two samples) and stating if a group of numbers are independent or dependent. </p> | g57922 | [
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<p>In <code>TraMineR</code> the function <code>seqient()</code> for calculating the entropy of a sequence object is not available for event sequences (as defined with <code>seqecreate()</code>). Does this mean that measures of "variation" does not make logical sense for event sequences? Are there alternatives to measur... | g27251 | [
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... |
<p>In Method of Moments for estimation, if there are $k$ parameters to estimate, we usually consider $i$-th moments, $i=1,...,k$, so that we have k equations for k unknowns.</p>
<ol>
<li>I wonder if it is wise to consider more moments of different orders,
i.e. $i$-th moments, $i=1,...,n>k$, so that we are to solve ... | g47937 | [
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... |
<p>Having equal number of cases across two groups (60 total cases), if one wants to perform a split-plot Anova and finds out that the Box's Test of Equality of Covariance Metrices is less than 0.001 then what does it mean?</p>
<p>I've read that it means that I have violated the assumption of multivariate normal distri... | g57923 | [
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<p>Before it is pointed, I am aware that a <a href="http://stats.stackexchange.com/questions/1576/what-are-the-differences-between-factor-analysis-and-principal-component-analysi">very similar question was already asked</a>. Still, I am in doubt regarding the concept.</p>
<p>More specifically, it is mentioned by the m... | g57924 | [
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<p>I need to calculate how many people I would need to screen to catch a disease in its early stages. If the disease has an R0 of 2, and starts with 1 infection in 1000, and I screen one person in every 1000 - how many people will the disease have reached by the time I screen an infected individual?
How can I do this ... | g57925 | [
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... |
<p>This might be related to game theory more than statistics, but I decided to ask this question here.</p>
<p>Let's assume you're offered a lottery. There are a hundred balls in a bowl: 99 white balls and one red ball. You are allowed to pick one ball at random (obviously without seeing what color it is). If the ball ... | g12756 | [
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<p>Feel free to critique my overall approach instead of answering my question directly.</p>
<p>I want to look at bivariate relationships among a binary outcome and multiple predictor variables before conducting multiple regression. EDIT: [The data are multiply imputed] and the categorical predictors have been dummy co... | g12758 | [
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<p>This is a pretty simple question. </p>
<p>If I win 7 dollars with a probability of 0.33, and 3 dollars with a probability of 0.35, can I substitue this multiscenario event to a single event of winning 7(33/68) + 3(35/68) with a probability of 0.68. </p>
<p>My goal is, given a money game, to quickly compare which s... | g57926 | [
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0.013123022392392159,
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-0.026829617097973824,
0.017202693969011307,
... |
<p>In Poisson Regression, suppose we have the following regression equation: $\ln(E(Y_i|X_1)) = \beta_0+ \beta_{1}X_{1}$ where $Y$ is the number of heart attacks. Also suppose $X_1$ is a binary variable (e.g. smokers versus non-smokers). How would you interpret the coefficient $\beta_1$? Smokers, on average, have $\exp... | g47073 | [
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0.06535745412111282,
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... |
<p>So far in the topic of principal component analysis, I seem to be jumping around in understanding these various topics, and have a few questions that I need to help solidify my overall understanding.</p>
<p>What I know how to do:
calculate eigenvalues from a covariance matrix.</p>
<p>My first question: Given a 2&t... | g12763 | [
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0.002403582213446498,
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0... |
<p>I am confused how to interpret the result of performing a normalized correlation with a constant vector. Since you have to divide by the standard deviation of both vectors (reference: <a href="http://en.wikipedia.org/wiki/Cross-correlation" rel="nofollow">http://en.wikipedia.org/wiki/Cross-correlation</a> ), if one ... | g12765 | [
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<p>Hotelling's $T^2$ distribution arises in testing differences between means of different populations. But is it often used? Can it be implemented in a modeling procedure, let's say, logistic regression?</p> | g57927 | [
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<p>This is a question to reflect some very basic understanding of the logic of the chi-square for a planned introductory essay. </p>
<p><em>[update] I've tried to improve the question with clearer examples and better focusing of the problems upon which I stumbled. It might still be a bit weak but I can't do bett... | g12767 | [
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<p>I am trying to understand power calculation for the case of the two independent sample t-test (not assuming equal variances so I used Satterthwaite).</p>
<p>Here is a diagram that I found to help understand the process:</p>
<p><img src="http://i.stack.imgur.com/S6P3Y.jpg" alt="enter image description here"></p>
<... | g57928 | [
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<p>I have run negative binomial and quasi-Poisson models based on an hypothesis testing approach. My final models using both methods have different covariates and interactions. It seems that there are no patterns when I plot my residuals in both cases. Thus, I was wondering which test I could use to see which model fit... | g12768 | [
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<p>I refer to the Simes (1986) paper found <a href="http://www-stat.wharton.upenn.edu/~steele/Courses/956/Resource/MultipleComparision/Simes86pdf.pdf" rel="nofollow">here</a>. In this setting, $P_{(1)}$ through $P_{(n)}$ are the order statistics of $n$ independent Uniform$[0,1]$ random variables and, for $0\le \alpha ... | g57929 | [
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<p>Given two independent MBA models 1 and 2 (each model is a set of rules with calcualted support, confidence and lift metrics) that were generated on subsets of large population of transactions, how to effectively compare rules between models? In particular, how to detect the biggest movers (up and down) from one mode... | g57930 | [
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<p>I have the following multiple linear regression model:</p>
<pre><code>Call:
lm(formula = Y ~ X1 + X2 + X2 + X3 + X4 + X5 + X6 + X7,
data = my.model, na.action = na.omit)
Residuals:
Min 1Q Median 3Q Max
-43.836 -1.507 0.010 1.485 46.231
Coefficients:
Estimate Std. Err... | g38084 | [
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<p>I've two groups of data, each containing an equal number of tuples. Each tuple is filled from observations of a phenomenon at regular intervals and are drawn from a discrete set. For each group we are observing independent phenomena, even though in each group they have the same characteristics.</p>
<p>I want to tes... | g41561 | [
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<p><a href="http://www.jstor.org/stable/177062?origin=crossref" rel="nofollow">Hedges et al. 1999, <em>Ecology</em> <strong>80</strong>: 1150-1156</a> reintroduces the old concept of using the natural logarithm of response ratio for ecologists as preferred statistics over p-values in comparative experiments and meta-an... | g12771 | [
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<p>I have two variables, each with the same set of 5 unranked possible values (let's call them A/B/C/D/E), and a set of data such as the following (A/A, A/D, B/B, D/D, E/E, B/A etc), where the first letter is the value of the first variable and second letter is second variable.
How would I show correlation between the... | g41567 | [
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<p>If $X$ is a continuous random variable, then let </p>
<p>$$\min_a{\mathbb{E}\:| X - a |} = \mathbb{E}\: | X - m |$$</p>
<p>Why is $m$ the median of $X$?</p> | g12772 | [
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<p>I have data from 50 human subjects, who are divided into groups A and B (30 participants are in group A and 20 participants in group B). I also have a range of measurements from each subject. I have used a machine learning algorithm (SVM) to predict the subject groups from the features using leave-one-out cross-vali... | g57931 | [
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<p>Taken from <a href="http://rads.stackoverflow.com/amzn/click/0412276305">Practical Statistics for Medical Research</a> where Douglas Altman writes in page 285:
<em>"...for any two quantities X and Y, X will be correlated with X-Y. Indeed, even if X and Y are samples of random numbers we would expect the correlatio... | g49699 | [
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<p>I am working with data from a complex survey, with over 100 variables per observation. From this I will be selecting 30 to 40 variables. All variables are categorical, with number of levels ranging from 2 to 23, with a mean of about five. </p>
<p>I would like to summarize my data with a log-linear model that highli... | g57932 | [
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<p>I'm testing the effect of four different altitudes (0m, 1000m, 2000m and 3000m) on repeated sprint performance (6 sprints at each altitude).
I have 8 test subjects who will be tested at each altitude. That means I'm getting 8x4x6=192 sets of data.
What I want to investigate is the difference in performance at the ... | g12774 | [
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<p>I am using Holt-Winters to do a time-series forecasting. The package chose gamma equal to 1 for me. I am wondering what that means. The prediction works pretty well overall.</p>
<p>When will you use this method and how do you choose the parameters of Holt-Winter? </p> | g57933 | [
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<p>I have two groups of people, a healthy population which has carriers of disease and non-carriers, and I have a sick population. I know the frequency of genetic variants in both groups. I want to know if I can say anything about the variants with any statistical certainty and how I would do that. </p>
<pre><code>... | g41570 | [
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... |
<p>This question is related to a previous post I've looked at (<a href="http://stats.stackexchange.com/questions/3249/calculation-of-seasonality-indexes-for-complex-seasonality">Calculation of seasonality indexes for complex seasonality</a>), but deals with more granular data (daily instead of weekly), and transforming... | g12777 | [
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<p>So I remember reading somewhere that when we have external regressors, <code>auto.arima</code> cannot make correct predictions for the order of difference for either seasonality or the main time series itself (correct me if I'm wrong!)</p>
<p>Now, I'd like to know whether we'd need to difference the external regre... | g57934 | [
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<p><img src="http://i.stack.imgur.com/Oxvip.png" alt="EM Algorithm"></p>
<p>The algorithm is used to classify english vs non-english tweets from unlabeled data. Given n observed tweets (x1 ... xn) where each tweet xi is a collection of d words (xi1 ... xid). y is the class (english/non-english). We use EM to estimate ... | g57935 | [
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<p>Before passing to question, let me briefly recap what's importance sampling of random variables is about. Suppose $\xi$ is a real-valued random variable with density $f$, and let $g:\Bbb R\to \Bbb R$ be some function. The task is to use Monte-Carlo to compute the integral
$$
\mathsf E[g(\xi)] = \int_\Bbb R g(x)f(x... | g57936 | [
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... |
<p>If I run Pearson correlation between Variable A (buyer/nonbuyer of ice-cream) and Variable B (buyer/nonbuyer of yoghurt) and have: </p>
<ul>
<li>Ho as "There is no relationship between...."</li>
<li>Ha as "There is a <strong>strong</strong> relationship..."</li>
</ul>
<p>then <strong>what would "strong" mean in th... | g49457 | [
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<p>I am running into some problems performing a multidimensional scaling image.
First of my dataset is quite large (330.000 fields: 33000 rows, 10 columns).
The output image needs to contain 10 dots, 1 for each column.
The fields in the dataset contain intensity values which first need to be converted to a distance mat... | g12779 | [
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<p>I am new to time series forecasting and have been slowly working my way through the different approaches available. I've so far mainly been using ets and arima models available in the R forecast package. As I need to forecast at a daily level taking into consideration weekends and public holidays, I have also been e... | g12780 | [
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<p>Consider the following R code and output:</p>
<pre><code>row1 = c(0,23,0,0)
row2 = c(0,1797,0,0)
data.table = rbind(row1, row2)
chisq.test(data.table)
Pearson's Chi-squared test
data: data.table
X-squared = NaN, df = 3, p-value = NA
</code></pre>
<p>Now consider the same in Python:</p>
<pre><code>import sc... | g57937 | [
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<p>Assume we have 2 random variables $(X,Y)$ with same distribution $G(.)$. Suppose we are interested in a joint probability of these r.v.'s without any information about dependence or correlation between these random variables. </p>
<p>Would it help to assume $X$ as a linear (or non-linear) function of $Y$? </p>
<p>... | g57938 | [
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<p>I'm having trouble understanding how to assess normality for discrete data. I understand the the K-S test is available to test the normality distribution for continuous data. However, what would be the equivalent for discrete data that have a Poisson or binomial shape? Would these be the chi-square and binomial te... | g47160 | [
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<p>I have temporal data of activity frequencies. I want to identify clusters in the data that indicate distinct periods of time with similar activity levels. Ideally I want to identify the clusters <em>without</em> specifying the number of clusters a priori.</p>
<p>What are appropriate clustering techniques? If my que... | g12784 | [
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0.03148709610104561,
0.014329449273645878,
-0.02800041437149048,
-0.025384370237588882,
-0.05942852422595024,
0.03804244101047516,
-0.04421025887131691,
0.0012063333997502923,
-0.01828833483159542,
0.030671274289488792,
-0.02478571981191635,
0.0677056834101677,
0.02539... |
<p>I am running a glmm with three fixed effects: </p>
<p>opponent 1 size ("1")<br/>
opponent 2 size ("2")<br/>
opponent 1 size - opponent 2 size ("diff")<br/></p>
<p>I am unable to run all three variables in the model at once because of the "diff" variable being correlated with the "1" and "2" variables. How, then, d... | g57939 | [
0.0307424645870924,
-0.02290133573114872,
0.014083526097238064,
0.0014195204712450504,
0.06433999538421631,
-0.013584712520241737,
0.0007208386668935418,
0.008694695308804512,
-0.08772973716259003,
-0.012974160723388195,
-0.009429004974663258,
0.04125107824802399,
0.005846264772117138,
0.0... |
<p>You sell 10 product on average every day. The model is based on a Poisson distribution.
To be enable to cover the indirect cost, the manager needs to sell 8 products per day.</p>
<p>Two questions:</p>
<blockquote>
<ol>
<li><p>What is the probability to sell between 0 - 5 products in a day?</p></li>
<li><p>Wh... | g57940 | [
-0.023689908906817436,
0.0388692244887352,
-0.007040712051093578,
-0.03919558972120285,
0.024584393948316574,
-0.060041919350624084,
0.041673753410577774,
0.00775547232478857,
-0.01157794613391161,
0.014682242646813393,
-0.07156075537204742,
0.016550298780202866,
0.011295049451291561,
-0.0... |
<p>Suppose the following distribution $p(x,y)$, $p:[0,1]^2 \to [0,+\infty]$ and:
$p(x,y) =
\left\{
\begin{array}{ll}
0 & \mbox{if } y>0 \\
+\infty & \mbox{if } y = 0
\end{array}
\right.$</p>
<p>i.e. we have:
$$p(y|x) =\delta_0$$
and $$p(x)=1$$</p>
<p>If this is the distribution that I want to sample... | g57941 | [
0.03107520379126072,
-0.06476645916700363,
0.005031030159443617,
-0.04359086602926254,
-0.024275675415992737,
-0.0688159242272377,
-0.0027822291012853384,
0.04293040186166763,
-0.03153533861041069,
-0.006308285985141993,
-0.010800684802234173,
0.03436068072915077,
0.017046106979250908,
0.0... |
<p>I am a clinical researcher and orthopedic surgeon and one of my PhD student is starting on the last part of her thesis. Her work is centered around the potential benefits of interprofessional teaching at an orthopedic ward. The study is a retrospective cohort study on register data for hip fracture patients. Our hyp... | g57942 | [
-0.0021419180557131767,
-0.0035626476164907217,
-0.0010612430050969124,
-0.07187063992023468,
-0.0211498960852623,
-0.028540384024381638,
0.005260911770164967,
0.055008415132761,
0.011442620307207108,
0.002875426784157753,
0.06150750070810318,
0.04325723275542259,
0.0016516835894435644,
-0... |
<p>I imagine this is a somewhat common situation in practice. I am thinking mainly in terms of preclinical drug trials.</p>
<p>1) During the course of the study a new technique is learned or some time/money is freed up to be able to use a new technique as a secondary outcome. </p>
<p>2) Some key piece of equipment br... | g12786 | [
0.02416975237429142,
0.002391660353168845,
0.01250708568841219,
0.025632591918110847,
-0.04331706091761589,
-0.015870431438088417,
0.03929813951253891,
-0.0025198524817824364,
-0.0226412583142519,
0.0055348435416817665,
0.05237181857228279,
0.004548066761344671,
0.02869577892124653,
0.0130... |
<p>Suppose I want to predict how many machine are going to fail in the next three years. The data collected are in days, so we want to predict no. of fails in next 1095 days. </p>
<p>All the machines (100 of them) started from, say, 1975 and until today, only 13 have failed. Now, I want to predict how many are going t... | g57943 | [
0.011481848545372486,
-0.0033311890438199043,
-0.0005168060888536274,
-0.034612108021974564,
-0.04477672651410103,
0.016209904104471207,
0.04733945429325104,
-0.00909352581948042,
-0.08538645505905151,
-0.003056930610910058,
-0.021877439692616463,
-0.0031266703736037016,
0.0982753112912178,
... |
<p>I have come across several usage of the term "heavy tail distributions", but unable to find some good resources in the Internet to answer few of my questions:</p>
<ol>
<li>Compared to what the tail of the distribution is said to be "heavy"?</li>
<li>Given some data, and their CCDF plots (a log-log plot, say) how do... | g12788 | [
0.04629324749112129,
0.05261716619133949,
-0.033338434994220734,
-0.0786864310503006,
-0.001913764514029026,
-0.0054077571257948875,
0.038583386689424515,
-0.009741444140672684,
-0.02980414219200611,
-0.028156863525509834,
-0.02706422284245491,
-0.010329208336770535,
0.0844409242272377,
-0... |
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