question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I need some kind of multivariate distribution which has the following properties</p>
<ul>
<li>support is $x_1,$ $x_2$, ..., $x_K$ where all $x_i \in [0,1]$</li>
<li>Though not required it is true that elements of the support will sum to 1. $\sum x_i=1$</li>
<li>the parameters of the distribution can be solved for i... | g66450 | [
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<p>I have 2 categorical variables with 8 unordered categories and multiple numerical variables and I want to train a logistic regression model. I want to test the independence between all my predictor variables, and remove the ones that are dependent, meaning that they are redundant in my model. </p>
<p>Is there any u... | g66451 | [
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<p>I need to prove the following identities for a factorial design experiment of the form $2^k$.</p>
<ol>
<li>$\overline{Y}(AB+)-\overline{Y}(AB-)=0.5[A(B+)-A(B-)]$</li>
<li>$A(B+)=A+AB$</li>
<li>$A(B-)=A-AB$</li>
<li>$A=[A(B+)+A(B-)]/2$</li>
</ol>
<p>($\overline{Y}(AB+)$ is the mean of all observations where A*B has... | g25450 | [
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<p>Would appreciate any responses and references if possible. Thank you</p> | g66452 | [
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<p>I hope I am including enough information here.</p>
<p>I am looking at the signal intensity of a tumor over time (calculated by the mean of the voxels). I would like to compare several tumors over an extended period of time (1 year) to see if the signal decreases, where the patient has been scanned every month.</p>
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<p>I am performing linear regression in R and I have a variable called diversityscore which is a value ranging from 1 to 10 indicating #activities a user performs with 1 meaning one activity to 10 meaning all ten activities. I am not sure if this is to be counted as a factor variable or a non-factor variable. How do I ... | g66453 | [
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<p>I am running a test that will have two conditions for a categorical IV. There are two categorical covariates and one continuous covariate. There will be four continuous dependent variables. What statistical tests will I need to run to analyze the data? This is a within subjects design and each participant will exper... | g66454 | [
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<p>I have two categorical datasets, say, $A$ and $B$, which are sparse. I would like to apply pairwise $\chi^2$ tests to a certain categories, which are sufficiently populated (say, have expected values $>5$) in the following way. Let $k_{A}$ be number of elements of $A$ which are $k$, and $\neg k_{A}$ be number of ... | g25452 | [
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<p>I'm having a set of free text from web. Since the users type their location in that field, we have many un-normalized city names. </p>
<p>For example, </p>
<p>"Shanghai, China"
"China, ShangHai" might mean the same city. </p>
<p>Note this is slightly different (should be easier) than NER since we know in this fie... | g66455 | [
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<p>I've performed an non linear regression with 3 variables and 5 parameters, using Wolfram Mathematica.
Now I want to detect the outliers that are far from 2*(standard deviation) of my function.
I've done a little software that investigate the outliers.
But now I'm wondering if this technique has got a statistical bas... | g66456 | [
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<p>If x$_{1}$, x$_{2}$,...,x$_{n}$ is sampled from N($\theta$$_{1}$, $\theta$$_{2}$), how can I prove that E [(x$_{1}$ - $\theta$$_{1}$)$^{4}$] = 3$\theta$$_{2}$$^{2}$?</p>
<p>I started off this question finding the completely sufficient statistics. This can be done because the normal distribution of of exponential cl... | g25454 | [
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<p>My questions are about Random Forests. The concept of this beautiful classifier is clear to me, but still there are a lot of practical usage questions. Unfortunately, I failed to find any practical guide to RF (I've been searching for something like "A Practical Guide for Training Restricted Boltzman Machines" by Ge... | g66457 | [
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<p>I have a 2x3 within-subjects design, with two different dependent variables (DVs). I would like to know if the two DVs are correlated or not.</p>
<p>Here is an example of what the data look like, e.g. a data frame in R:</p>
<pre><code># Make some data:
set.seed(1154)
data <- data.frame(id=gl(10, 6),
... | g66458 | [
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<p>Hi I wanted to know if there are some good books on text mining and classification with some case studies?. If not some papers/journals accessible to public would do. If they illustrate their examples with R even better.
I am not looking for step by step manual but something which illustrates the pros and cons of v... | g49505 | [
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<p>It a simple school problem with five different parts. I understand a), b), c), and e); however I am very confused on what d) means. The problem goes like this:</p>
<p>"Suppose that each day the price of a stock moves up 1/8 of a point, moves down 1/8 of a point, or remains unchanged. For i>=1, let U_i and D_i be... | g25457 | [
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<p>I have a question related to hypothesis testing. I cannot seem to find error in my reasoning.</p>
<p>Initial question:
We have 230 patients: 157 males and 73 females. 142 males are sick and 69 females are sick. Can we say that females are sick "statistically significantly" more?</p>
<p>My method:<br>
Assume that f... | g66459 | [
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<p>I fitted a mixture denstiy of two gaussians two my data. I now want to calculated the standard errors of the estimates via the boot.se command of the mixtools package. My question is now, if the output is correct? It seems a bit odd to me, so is this correct what I am doing and can I rely on the values?</p>
<p>My d... | g25458 | [
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<p>Suppose we have training data set and a test data set. The outcome variable is binary. Is it usually necessary to split the training data set so that there is a cross validation data set? Or can you use the whole training data set to build a model and the use this model on the test data set? For logistic regression,... | g33040 | [
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<p>A set of points $X = \{x\}$ is $\gamma$-shattered by a set of functions $\mathcal{F}$ if there are real numbers $r_x$ indexed by $x$ such that for any binary vector $b$ defining labeling of points from $X$ we can find a function $f \in \mathcal{F}$ such that $f(x) \geq r_x + \gamma$ if $x$ has label 1 and $f(x) \leq... | g25460 | [
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<p>I have a vector of numbers that I've uploaded here (alrig.com/code/MyData.Rdata) using dput. </p>
<p>I would like to get the bca ci so I've written this code:</p>
<pre><code>my.mean <- function(dat, idx){
return (mean(dat[idx], na.rm = TRUE))
}
boot.out<-boot(data=my.data, statistic = my.mean, R=1000)
</c... | g66460 | [
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<p>Sometimes multiple tests are conducted of the same hypothesis, using the same model each time but with some model parameter changed. As results for similar values of the parameter are similar, this can be viewed as a calibration of the model rather than data dredging folly. Here's an example:</p>
<p><img src="htt... | g66461 | [
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<p>Some of the features I am working with has more than 300 factor levels. I tried to reduce their number of levels with a 'fake dummy' method. For example, I replaced one 600-level predictor with 4 predictors (as $600<5^4$). Is this a valid approach?</p> | g66462 | [
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<p>I am running a two-way ANOVA with one random variable. My histogram of the residuals is showing considerable (negative?) skew:
<img src="http://i.stack.imgur.com/1YxxC.jpg" alt="enter image description here"></p>
<p>And my Q-Q plot of the residuals shows a corresponding U-shaped curve: </p>
<p><img src="http://i... | g25466 | [
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<p>In my opinion, these two RMSEs are proportion related. I use the training set to get 10-fold CV RMSE and get a model on the whole training set to predict on the test set. As the training set is larger than the 10-CV training set, the RMSE score on the test set should be better than the 10-CV training set. However, I... | g66463 | [
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<p>From my model, I'm asked to determine which variables are statistically significant. </p>
<pre><code>fitted.model <- lm(spending ~ sex + status + income, data=spending)
</code></pre>
<p>My results were as follows:</p>
<pre><code>Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Inte... | g25469 | [
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<p>I don't quite understand "by the properties of the Fourier transform, $it^r\psi(t)$ is the Fourier transform of $(-1)^rD^r\Psi(x)$" from <a href="http://en.wikipedia.org/wiki/Edgeworth_series" rel="nofollow">Wikipedia</a> about Gram–Charlier A series and Edgeworth expansion:</p>
<blockquote>
<p>We examine a cont... | g66464 | [
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<p>I have two samples, say sample A and B, and a negative control. </p>
<p>I expect that the sample A to be different than the negative control, so I use a t-test to check for that. </p>
<p>Then, I expect sample B not to be different from the negative control. How do I test for that? I could use a t-test for that too... | g25473 | [
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<p>Just figuring out statistics on my own after doing a psycholinguistics study for my undergrad thesis (never taken a statistics class). </p>
<p>Basically, the experiment recorded subjects' reaction times to different classes of idioms (and control strings). So I'm trying to see if reaction times differ significantly... | g66465 | [
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<p>I have a (fairly smooth) function $f$ and a sample $\{(x_i,y_i)\}_{i=1,\ldots,N}$ from the joint
distribution of the random variables $X$ and $Y$. I would like to estimate the conditional
expectation function $g(y) = E(f(X) \;|\; Y=y)$ non-parametrically.</p>
<p>The random variables $X$ and $Y$ are either two or t... | g66466 | [
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<p>I developed a modified version of Latent Dirichlet Allocation (LDA).</p>
<p>What is the standard way to validate the LDA algorithm?</p>
<p>Is using the log likelihood a good approach? What validation strategy do current implementations use?</p> | g25474 | [
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... |
<p>I am trying to do a study to determine if average annual temperature is related to number of cases of a particular disease. I have data for 15 different states over ten years. I have done multiple transformations and cannot get the average annual temperature to be approximately normally distributed. Does any one hav... | g66467 | [
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<p>I have read in a recent article that, with the use of Martingale residuals in a Cox regression analysis, one can better categorize a variable (different cut-offs).
I have computed them using SPSS v19 (compute martingale=(status=1)-HAZ_1, whare HAZ_1=cumulative hazard function).
Now..how can I find these cut-offs?
... | g66468 | [
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<p>A textbook I am using (Field's "Discovering Statistics Using SPSS") declares that "the simplest way" to work things out is to calculate SS<sub>A×B</sub> as SS<sub>BETWEEN</sub> - SS<sub>A</sub> - SS<sub>B</sub>. </p>
<p>This left me wondering if there might be some other way to calculate SS<sub>A×B</sub>. I'm espec... | g66469 | [
0.022227969020605087,
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<p>There is a sample of n values that are the first n largest values of a population.
Is there a way of getting any statistic such as mean or dispersion from such piece of information provided that the population is normally distributed with its size either known or unknown?</p> | g66470 | [
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<p>This problem is somewhat involved and I have a partial solution so bear with me. I will illustrate the problem with an example. Lets say we have two processes and we want to know which has a higher success rate. So we do two sets of trials. process 1 gives 53 out of 606 and process 2 gives 32 out of 595. So the rate... | g25479 | [
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<p>I have a list of seven samples from an incubation series with frequency of occurrence for, say, 30 species from each treatment. Typical observations within each bottle are >5000 (DNA sequences). There is a time zero sample (not replicated) and a sample after several days exposure to three chemical treatments (dupli... | g25480 | [
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<p>I am working on a project (not homework) and would like to know if I am just fundamentally misguided. </p>
<p>Basically, let say we have some data $Y, X_1$ and $X_2$.... where $X_1$ and $X_2$ are matrices. If I create an orthogonal projection of $X_1$ relative to $X_2$... something like this (R code; please corre... | g25482 | [
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<p>I'm reading A. Agresti (2007), <em><a href="http://rads.stackoverflow.com/amzn/click/0471226181" rel="nofollow">An Introduction to Categorical Data Analysis</a></em>, 2nd. edition, and am not sure if I understand this paragraph (p.106, 4.2.1) correctly (although it should be easy):</p>
<blockquote>
<p>In Table 3.... | g25484 | [
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<p>For two normally distributed samples, is there a way to test for $H_0: \mu_1=\mu_2$ and also $\sigma_1^2=\sigma_2^2$. I have computed the likelihood ratio, but cannot recognize the underlying distribution.</p> | g66471 | [
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<p>I'm hoping that someone could suggest a tool for viewing conditional probabilities withi. I am currently using Weka, but the ability to view the conditional probability tables of nodes within the Network is not the easiest to read.</p>
<p>Any suggestions on tools out there, or perhaps a workflow in R that can help... | g45809 | [
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<p>I am trying to come up with a model that can predict movie box office. One factor that is important is competition... I want to model it as a function of several variables, including some that are variables in their own right in this fuller model.</p>
<p>One- if a variable would be counted twice, should I even do i... | g66472 | [
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<p>Having a bit of a problem with this question:</p>
<p>A screening test for Meningitis is known to provide a positive result 95% of the time when a patient with Meningitis is tested, while it gives a negative result for 70% of patients tested who are not suffering from the disease. National statistics suggest that 5%... | g38021 | [
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<p>According to the rule of marginality, I should <strong>remove all non-significant interactions</strong> from model to achive simplicity (MInimal Adequate Model).</p>
<p>I am familiar with removing such interactions from <strong>simple linear models in R</strong>.</p>
<p>For example if the triple interaction will b... | g25485 | [
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<p>I'm fitting a logistic regression model Y ~ X1...X10 to 10,000 observations, where my goal is estimate the effect of each covariate on Y.</p>
<p>My first issue is deciding what transformations to apply to the predictors. They all have very skewed distributions, and in some cases take on very few (<6) values. I i... | g66473 | [
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<p>In a frequency distribution the upper boundary of each class interval has a constant ratio to the lower boundary. Show that the Geometric Mean $g$ can be expressed as $$\log g=a+\dfrac{k}{n}\sum_{i=1}^r f_i(i-1)$$</p>
<p>where $a$ is the class mark of the first class, $k$ is the logarithm of the ratio between uppe... | g66474 | [
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<p>I have a question regarding Partitioning Around Medoids (PAM) clustering algorithm, because everywhere I look, it is described differently. In every step of the algorithms do I swap only one medoid or more? </p>
<p>I mean, does the swapping step look like:</p>
<pre><code>For each cluster medoid m in 1..K
Find ... | g66475 | [
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<p>I've recently built a survival model with time-varying covariates (assuming equal time periods) using R and I am now in the process of putting this into Oracle for production using just the coefficients from the model. The goal is to score new data that comes in each day in order to produce a cumulative hazard estim... | g767 | [
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<p>I read that in order to test whether 2 paths in a structural equation model significantly differ from each other, you have to compare one model in which both paths are allowed to differ with a second model in which they are constrained to be equal. Now I know how to constrain the non-standardized path coefficients t... | g25487 | [
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<p>I am trying to learn to use libsvm, I have used some defalut training sets to generate the plots by grid-search and obtained a plot below.</p>
<p>I want to know,</p>
<ul>
<li><p>What type of plot is this,</p></li>
<li><p>What does it really tells us,</p></li>
<li><p>How to understand and analyze this plot.</p>
<... | g66476 | [
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<p>I have a set of independent random walkers on a graph that produce a distribution of the nodes in that graph. I would like to test whether the random walkers have produced a distribution which is consistent. </p>
<p>I thought about separating the results from the random walker into various sets, eg 4 separate group... | g25489 | [
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<p>I have a proportion value computed on a weekly basis with 95% confidence interval. Now I want to get the proportion on a daily basis, instead. Assuming the values are uniformly distributed, I divided my proportion into 5 (that's for 5 days). Will my variance stay the same?</p> | g66477 | [
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<p>I want to run a random effect quantile regression with repeated subjects. The subjects bid on two different steaks and I have demographics as explanatory variables. Can this be done in SAS?</p> | g50 | [
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<p>I have data that I'm trying to classify into two different groups using Fisher linear discriminant analysis. This gives me a vector of weights $\vec w$, used in the equation $\vec w\cdot \vec x$ to give a value that's compared to a threshold in the classification stage.</p>
<p>What I'd like to know is, what kind of... | g348 | [
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<p>Although it is unknown dice, the symmetry of the evidence tells us, that we can treat the dice as fair, so the chance should be exactly 50%.</p>
<p>But if we simulate it by hand, the result is less then 50%:</p>
<ul>
<li><em>Mathematica code</em></li>
</ul>
<p></p>
<pre><code>In[1]:= nsym = 200000 (*Some very la... | g66478 | [
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<p>I have a set of data. For example, 10,000 observations.
Each set has the same format.
Each set has 3 to 10,000 records.
The question is, what kind of sampling method is reasonable to do with this set of data?</p>
<p>Need some rationale and explanations.</p>
<p>I am a programmer but assigned to this stats job, and... | g66479 | [
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<p>I have observed a number ($n=6$) of events and want to test the null hypothesis that they are Poisson distributed with a known parameter $\lambda\approx1$. But I don't know exactly when I started and stopped observing, only when my first and last observation are. How can I test this hypothesis while avoiding the bia... | g66480 | [
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... |
<p>There appear to be a large number of rules of thumb for histogram bin size and kernel selection for density plots. Are histograms and/or density plots really the best visualization for a single continuous variable? Are there other desirable options? Are there any settled best practices for visualizing continuous dat... | g66481 | [
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<p>For my research I am using Labelled Latent Dirichlet Allocation (L-LDA) on Reuters-21578 ModApte split dataset. In this dataset the news stories have a title and a body. To test the effect of L-LDA, I apply it in on all three combinations, thus <strong>Title</strong>, <strong>Body</strong> and <strong>Title&Body... | g66482 | [
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<p>In a multiple regression model is the independent variable with the largest weight (coefficient), the one that expains the dependent variable the most?</p> | g2416 | [
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0.007385190576314926... |
<p>I have a set of features and a score in my dataset. Score is defined based on these features. What technique is used to see which of the features is more effective in the total score?
I used anova and I can see from p-value which feature is significantly different. Can anybody propose any other method.
THanks</p> | g66483 | [
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<p>In a regression model with dummy variables, how does one check for intearction between the dummy variable and the independent variables?Wouldn't there be problem of multicollinearity when such interactions are condsidered?</p> | g66484 | [
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<p>I am in the process of validating a five-items scale for measuring dependence on substance 'X'. I have collected data from 98 people who used the substance under consideration at least once weekly for three years. The items showed a good internal consistency (Cronbach's alpha = 0.81). I also did factor analysis. The... | g66485 | [
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0.0... |
<p>From a questionnaire survey I have 44 statements (items) which were supposed to measure 11 bases of power (factors). Four items per factor. Since this survey was only slightly altered from its well established original source, it is expected that eleven factors are actually measured. The number of observations is 25... | g25500 | [
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<p>My question is probably elementary, and I apologize for that. I am reading Kogan's "Introduction to Clustering Large and High-Dimensional Data"; I am interested in understanding batch K-means and K-means and use it in $\operatorname{R}$. In the textbook it is stated that both algorithms need an initial choice of</p>... | g25501 | [
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<p>I am trying to model <strong>count data in R that is apparently underdispersed</strong> (Dispersion Parameter ~ .40). This is probably why a <code>glm</code> with <code>family = poisson</code> or a negative binomial (<code>glm.nb</code>) model are not significant. When I look at the descriptives of my data, I don't ... | g66486 | [
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<p>In a numerical low rank decomposition, whether it is non-negative matrix factorization(NMF), or binary matrix factorization(BMF), or non-negative sparse PCA, we have two low-rank matrices to approximate the original matrix by multiplying.</p>
<p>M = U * P </p>
<p>whose dimensionality being:</p>
<p>M: n*m , U: n*k... | g66487 | [
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<p>I hit the following problem: I calculated the p-value of a chi-square test, which gave me a result near 1 and clearly does not lead to rejection. On the other hand, I determined the power of the same test as 6%, which means a type II error
of 94%. This situation would imply non-rejection as decision, which is wrong ... | g66488 | [
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<p>I am evaluating a dataset of ~400 subjects and 10 covariates trying to fit a Cox ph model for predicting survival in AML patients. </p>
<p>To evaluate the models I am using a bootstrapping procedure of 50 iterations (sampling with replacement). Models are built on the training set and tested on the test set.
For ea... | g66489 | [
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<p>I'm trying to make overlaid ROC curves to represent successive improvements in model performance when particular predictors are added one at a time to the model. I want one ROC curve for each of about 5 nested models (which I will define manually), all overlaid in one plot. For example:</p>
<pre><code> #outcome ... | g66490 | [
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<p>I am thinking of building a model predicting a ratio a/b, where a <= b, a > 0, b > 0. So, the ratio would be between 0 and 1. For independent variables, I have a continuous one and several 0/1 indicators.</p>
<p>I could use a linear regression, although it doesn't naturally limit to 0..1. I have no reason to b... | g25504 | [
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<p>I have a probability density function in R and I want to draw a single sample from it. How do I do that?</p>
<p>My current solution (and the one Google keeps giving me) is to evaluate the function for a dense set of values (<code>x</code>) giving the associated probabilities (<code>px</code>) and then draw a sample... | g25505 | [
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<p>I've been working on putting together a survival analysis using Kaplan-Meier and the logrank test. I am doing the testing in R with survdiff(). Each plot has multiple groups/curves, and I've been testing for the difference between groups (where there are more than two) by doing individual pairwise tests, as has been... | g66491 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/28942/computing-and-plotting-a-correlogram">Computing and plotting a correlogram</a> </p>
</blockquote>
<p>I have spatial data for a grid of size 20x20. I wanted to know how I can plot a correlogram to see... | g49752 | [
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0.01713... |
<p>As per the heading, is it possible to add AIC to some previously computed models based on the stats I have (which include $r^2$, its p-value, $\sigma$ for each variable individually)?</p>
<p>They are all bivariate models, though with some calibration parameters (I know the number of parameters in each model to feed... | g5029 | [
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<p>I want to do power computation for testing differnce between two log normal means with R. Can you write using R code?
best wishes...</p> | g66492 | [
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<p>I'm working on a word-prediction/spelling-correction software project and I need to calculate the probability that a dictionary word is what the user meant to type, referred to as a "score". I found an article that explains how to score matches using statistical techniques, but I don't understand it 100% (I'm not st... | g66493 | [
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<p>I have a random variable $X\sim \text{Normal}(\mu,\sigma)$ and have the transformation $Y=\max\{0,X\}$. Is the distribution of $Y$ a truncated normal where it is truncated to live on the positive half of the real line?</p>
<p>Secondly, is there a closed form solution for the joint distribution of a Normal random v... | g5030 | [
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<p>Most of teaching videos and materials about binary logistic are using more than one predictor in their examples.</p>
<p>My question can you run binary logistic regression (for smoking or not outcome) with only one predictor whether it is continuous or dichotomous such as age and gender respectively and separately <... | g66494 | [
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<p>I have a question regarding cluster analysis. </p>
<p>I was wondering if I have only 9 data points, is it valid to use k-means methods in cluster analysis?</p>
<p>I have done a special molecular evolution analysis and it has generated 9 points, what I want to know is that whether there is any clustering among the ... | g25508 | [
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<p>I need the description of Huber sandwich estimate method for quantile regression.</p>
<p>I found this "a Huber sandwich estimate using a local estimate of the sparsity function". Sparsity function looks like $s(\theta)=f(F^{-1}(\theta))^{-1}$, $F$ is a distribution of residuals and $f$ is a density function of $F$... | g66495 | [
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... |
<p><br>Currently I'm using svm to classify the test samples to two different classes (True and False). When I use multi class classification, I have both true and false samples in my training set, the accuracy is always above 90%, but if I use one class classification (only true samples in the training set), the accura... | g66496 | [
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0.0312... |
<p>I am trying to extract the variance-covariance matrix of the residuals of a generalized linear mixed-effects model that was fitted using lmer (of the R package lme4), but this does not seem to be straightforward. Does anybody knows how this can be done?</p>
<p>Thanks,</p>
<p>Regards,
Willem </p> | g25510 | [
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<p>I have a bunch of features that I'm trying to measure before and after applying a certain process. I want to see if the process I'm applying is changing the relative orientation of the features among themselves.</p>
<p>Measurement of feature "i" results in a 3D point of the form (Xi, Yi, Zi). The catch is that I ha... | g25514 | [
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<p>I have completed my data analysis and got "statistically significant results" which is consistent with my hypothesis. However, a student in statistics told me this is a premature conclusion. Why? Is there anything else needed to be included in my report?</p> | g49823 | [
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<p>Is it logical to say that you can increase statistical power by having a highly sensitive outcome measure? I say this because a highly sensitive test has low Type II error, and low Type II error leads to high power. In one of the articles I was reading, the authors' power analysis revealed that they only needed 6 pa... | g66497 | [
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<p>Is logistic regression a correct way to identify the relationship between <code>lead source</code> (an independent variable), demographics (e.g., <code>gender</code>, <code>income</code>, etc., independent variables) and <code>lead outcome</code> (yes or no, my dependent variable)?</p>
<p>More details:</p>
<p>The ... | g25519 | [
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0.0... |
<p>When computing AIC,</p>
<p>$AIC = 2k - 2 ln L$</p>
<p>k means 'number of parameters'. But what counts as a parameter? So for example in the model</p>
<p>$y = ax + b$</p>
<p>Are a and b always counted as parameters? What if I don't care about the value of the intercept, can I ignore it or does it still count?<... | g66498 | [
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<p>I am reading about Metaelliptical copulas but I don't know the difference between elliptical Gaussian and multivariate Gaussian distributions I would appreciate if somebody can explain the difference in a simple way.
This is the paper that I was reading in case if you need more clarification.
<a href="http://onlinel... | g66499 | [
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<p>As part of my statistical mechanics class, I'm trying to go through Kardar's statistical physics of particles and I'm having trouble with this one line:</p>
<blockquote>
<p>Consider the sum $X=\displaystyle \sum_{i=1}^N x_i$, where $x_i$ are random variables with a joint PDF of $p(\mathbf{x})$. The PDF of $X$ is... | g66500 | [
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<p>Suppose a number of random variables (call them "errors") observed for different "scores". For every score 11 errors have been observed. See the plot below to get the picture:</p>
<p><img src="http://i.stack.imgur.com/dgJ6Y.png" alt="enter image description here"></p>
<p>I would like to know in what scores the err... | g66501 | [
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<p>I'm analysing reaction time data from a grammaticality judgement task (collected in a masked-priming experiment). The stimulus were noun-noun compounds, including 3 types of compounds (depending on semantic relation). Each compound was tested 4 times, in a 2x2 design (prime = N1 or N2; order = grammatical or ungra... | g66502 | [
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<p>What R packages should I install for seasonality analysis?</p> | g38208 | [
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<p>After taking a statistics course and then trying to help fellow students, I noticed one subject that inspires much head-desk banging is interpreting the results of statistical hypothesis tests. It seems that students easily learn how to perform the calculations required by a given test but get hung up on interpreti... | g49294 | [
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0.00... |
<p>Which methods are used for testing random variate generation algorithms?</p> | g49380 | [
0.028067803010344505,
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0.0005826384294778109,
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0.005962760653346777,
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0.005647683050483465,
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0.013180005364120007,
0.026187565177679062,
... |
<p>There is an old saying: "Correlation does not mean causation". When I teach, I tend to use the following standard examples to illustrate this point:</p>
<ol>
<li>number of storks and birth rate in Denmark;</li>
<li>number of priests in America and alcoholism;</li>
<li>in the start of the 20th century it was noted t... | g49789 | [
0.05858931317925453,
0.044641152024269104,
-0.008930935524404049,
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0.024353673681616783,
0.045915015041828156,
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0.05949351191520691,
0.021273743361234665,
-0.035696841776371,
0.03318192809820175,
-0.03247940167784691,
0.0887056440114975,
0.05086914... |
<p>I have a data set that I'd expect to follow a Poisson distribution, but it is overdispersed by about 3-fold. At the present, I'm modelling this overdispersion using something like the following code in R.</p>
<pre><code>## assuming a median value of 1500
med = 1500
rawdist = rpois(1000000,med)
oDdist = rawDist + ((... | g25531 | [
0.013268704526126385,
0.002863067202270031,
-0.016693830490112305,
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-0.017918480560183525,
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0.003444328671321273,
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-0.04521104693412781,
0.04804180562496185,
-0.02012808434665203,
0.04369071498513222,
-0.... |
<p>Participants were rated twice, with the 2 ratings separated by 3 years. For most participants the ratings were done by different raters, but for some (< 10%) the same rater performed both ratings. There were 8 raters altogether, with 2 doing ratings at both time points. </p>
<p>Now, since the ratings were of an ... | g66503 | [
0.016286710277199745,
-0.048274699598550797,
0.00735646253451705,
-0.024554090574383736,
0.015610591508448124,
0.02184678614139557,
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0.029650283977389336,
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0.023106781765818596,
0.06192236393690109,
0.029095740988850594,
-0.028830304741859436,
-0... |
<p>I own around 40,000 text files for preprocessing (in purpose of document classification). I used R (with tm package) for prototype and now looking for a equivalent Java library for products. </p>
<p>However, for very fundamental tasks, i.e. text preprocessing, I found a very strange problem. That, with Weka, I appl... | g25532 | [
0.01754593476653099,
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0.03058796375989914,
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0.042056623846292496,
0.03414957597851753,
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0.014198563992977142,
0.0088865477591753,
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0.010301890783011913,
0.04236... |
<p>I am using Fisher's combined test to fuse several different independent tests. I have a problem understanding the results in some cases.</p>
<p>Example:
Let's say I run two different tests, both with the hypothesis that mu is smaller than 0. Let's say that n is identical and the two samples have the same calculated... | g45864 | [
0.009633960202336311,
-0.032003991305828094,
0.017674844712018967,
0.021767815575003624,
0.021857623010873795,
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0.0052165561355650425,
0.05332926660776138,
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-0.02789948880672455,
0.002235355554148555,
0.004291840363293886,
0.0131969740614295,
0.02... |
<p>I have a simple time series of one hour intervals:</p>
<pre><code>library('forecast')
# load an hourly time series of points
usage <- ts(scan('http://cl.ly/102L0j3o1p2m0m3p0t2o/usage'), frequency = 24)
plot.ts(usage)
</code></pre>
<p>the Holt-Winters forecast looks as expected. <a href="http://cl.ly/081o3I1P2A... | g45867 | [
-0.034574639052152634,
-0.03787824884057045,
-0.005378205794841051,
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-0.04717466980218887,
0.049265701323747635,
0.019460445269942284,
0.06014121323823929,
... |
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