question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I have read in a huge number of papers that sparse models (sparse coding, dictionary learning, sparse matrix factorization, ...) are good solutions for image denoising problems.</p>
<p>I know that representing data as sparse combinations of atoms from a (overcomplete) dictionary should be the way the mammal primary... | g15720 | [
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<p>I have data about seed predation (SP) in fruits of three differents colors (yellow, motted, dark) and in two fruiting seasons (2007, 2008). I performed a GLMM and the outcome showed that the interaction term (color:season) was significant, and some combinations of this interaction have significant Pr(>|z|), but I do... | g59908 | [
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<p>I am probably dealing with a problem that has probably been solved a hundred times before, but I'm not sure where to find the answer.</p>
<p>When using logistic regression, given many features $x_1,...,x_n$ and trying to predict a binary categorical value $y$, I am interested in selecting a subset of the features w... | g45071 | [
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<p>I know there are already several threads on this, but none seem to explicitly cover what I want. I have a set of financial data (pulled straight from Bloomberg) and am trying to fit a t-distribution (with theoretical discussion of MLE).
I know it can't be solved in closed form and am looking at EM and Newton-Raphson... | g59909 | [
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<p><img src="http://i.stack.imgur.com/QbZ5T.png" alt="Consider the following plot."></p>
<p>I want to identify the regions that are considerably higher than the highest cluster. (The obvious regions which should be identified as their own clusters, notably at the x coordinate ~10 e+07. How would I be able to identify ... | g16805 | [
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<p>I want to know how variables affect travel mode for different trip purposes (i.e. leisure trips, work trips and shopping trips) in a specified region. I have 450 respondents in three different neighborhoods. My dependent variable is mode of travel (in 5 categories including walking, public transport, taxi, private c... | g59910 | [
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<p>What is the difference among target population,study population and theoretical population ?</p> | g59911 | [
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<p>I am doing my dissertation, and I am conducting a number of tests. After using a Kruskal–Wallis test, I usually report the result like this: </p>
<blockquote>
<p>There is a significant difference $(\chi^2_{(2)}=7.448, p=.024)$ between the means of...</p>
</blockquote>
<p>But now I conducted a Mann–Whitney test, ... | g59912 | [
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<p>I'm reading a <a href="http://arxiv.org/pdf/1011.4071.pdf" rel="nofollow">paper</a> that defines a function $f_w(x)$ that takes input $x$ and parameters $w$ and a set of constraints. There are also training data. The aim is to find the set of parameters $w$ that respect the constraints. The authors then defined the ... | g59913 | [
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<p>I don't understand how sometimes given an optimization problem, a function could get its optimal solution by minimizing or sometimes just by reformulation it becomes maximizing. Can you please give me an example for this?</p> | g15725 | [
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<p>This is a question that landed on my desk, and I don't have the requisite experience to reply.</p>
<p>A researcher has been asked to perform (by a journal reviewer) a two-way factorial ANCOVA on some microrarray data (a single array will be a single measurement of ~30,000 entities from a single sample in this case)... | g15727 | [
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<p>How do I fit a linear model with autocorrelated errors in R? In stata I would use the <code>prais</code> command, but I can't find an R equivalent...</p> | g59914 | [
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<p>Would like to know how confident I can be in my $\lambda$. Anyone know of a way to set upper and lower confidence levels for a Poisson distribution? </p>
<ul>
<li>Observations ($n$) = 88 </li>
<li>Sample mean ($\lambda$) = 47.18182</li>
</ul>
<p>what would the 95% confidence look like for this?</p> | g15729 | [
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<p>I would like to validate the standard deviation which a model reports, because I think it is underestimated, because in the procedure some model selection is involved.</p>
<p>After running the model on a validation set, it became clear to me that the standard deviation were indeed grossly underestimated. </p>
<p>I... | g59915 | [
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<p>I have tested the <a href="http://en.wikipedia.org/wiki/Cluster_Analysis#Fuzzy_c-means_clustering" rel="nofollow">fuzzy C-means (FCM)</a> algorithm using the R function <code>fanny</code> from the <code>cluster</code> package and I have wrote my own FCM algorithm to have more control on the distance function. The pr... | g59916 | [
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<p>What software does one use to create a map that describes conditions over an arbitrary area ? The example I am thinking of would be a map of the US where states that voted one way or another would be red or blue. Obviously I can get a map of the US and use a graphics program to manually paint in the states, but I am... | g59917 | [
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<p>I am trying to model the time lapse between when a user sees an ad and when they call the advertiser (presuming they do). I have two issues - part of the data seems exponential, but I am wondering if there is a similar distribution with an extra parameter because I cannot quite get it to fit. Also, the peak does n... | g59918 | [
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<p>Currently, I am working on a count data set measuring events in a third-order administrative unit. The frequency of events varies for each third-order administrative unit to account for the variability, I am using a negative binomial regression model. </p>
<p>A crude graphical analysis of the residual of the regres... | g59919 | [
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<p>I have a question regarding the use of dmnorm in Jags when none of the mean and variance covariance matrix are known and fixed. I keep getting the error "node Q invalid parent value"
I am not sure where the issue comes from. Any idea will be more than welcome! Thanks!</p>
<pre><code>model {
for (i in 1:n) {
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/18434/r-squared-x-explains-the-percentage-of-variation-of-the-y-values-does-axis-o">R-squared: X “explains” the percentage of variation of the Y values. Does axis order matter?</a> </p>
</blockquo... | g49574 | [
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<p>I'm looking into the possibility of using a non-causal time series filter for some data. The goal is filtering (for the purpose of anomaly detection). However, this is not particularly relevant.</p>
<p>I'm wondering how simulation of such a time series would work? Say for example your time series model were:</p>
<... | g59921 | [
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<p><strong>The Problem</strong></p>
<p>Consider the aging chain on $\{0, 1, 2, \dots\}$ in which for any $n \geq 0$ the individual gets 1 day older from $n$ to $n+1$ with probability $p_n$ but dies and returns to age 0 with probability $1 - p_n$. Find conditions on the $p_n$'s that guarantee that:</p>
<p>(a) 0 is rec... | g59922 | [
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<p>I am trying to get some ideas on how to test for an implicit relationship, if any, between variance and skewness. That is, given a very large data set (e.g 90 years of monthly returns), is there a way to generally test if skewness is likely to increase with increasing variance or vice versa?</p>
<p>I will be very ... | g59923 | [
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<p>In Rosenthal and Rubin (1979) ``A Note on Percent Variance Explained as A Measure of the Importance of Effects'', they give an example of where $r^2$ is deceptively low:</p>
<blockquote>
<p>Suppose half the patients in a medical study are randomly assigned to a new medical treatment (X = 1) while the other half a... | g15748 | [
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<p>We call the integral of a <a href="https://en.wikipedia.org/wiki/Probability_density_function" rel="nofollow">probability density function</a> (PDF) a <a href="https://en.wikipedia.org/wiki/Cumulative_distribution_function" rel="nofollow">cumulative distribution function</a> (CDF).</p>
<p>But what's the cumulative ... | g59924 | [
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<p>For the LASSO (and other model selecting procedures) it is crucial to rescale the predictors. The <a href="https://vimeo.com/72420767" rel="nofollow">general</a> <a href="https://vimeo.com/72414394" rel="nofollow">recommendation</a> <a href="https://vimeo.com/72666579" rel="nofollow">I follow</a> is simply to use a... | g59925 | [
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<p>Actually I want to see the impact of Investors sentiment on Aggregate stock market return, so my major concern is to identify the impact of investors sentiment.</p>
<p>But besides investors sentiment I want to include 5 more Independent variable which might have impact also stock market return.</p>
<p>Its a single... | g10200 | [
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<p>I have 1750 proteins that I want to compare the expression level of them between 3 groups (cell-type) using R. How can I do it?</p> | g15755 | [
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<p>Also posted <a href="http://mathoverflow.net/questions/86936/minimum-distance-estimation-of-mixed-mixture-distributions">here</a> and <a href="http://math.stackexchange.com/questions/459747/how-to-mix-probability-estimators-of-the-same-phenomenon">here</a>.</p>
<p>I have the following problem:</p>
<p>I have N mode... | g59926 | [
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<p>I am reviewing a paper where I found this sentence repeatedly:</p>
<blockquote>
<p>A is statistically insignificantly worse than B</p>
</blockquote>
<p>I consider this to be confusing since, for me at least, it is not immediately clear if it is the same as:</p>
<blockquote>
<p>A is not statistically significa... | g59927 | [
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<p>Kernel methods are very effective in many supervised classification tasks. So what are the limitations of kernel methods and when to use kernel methods? Especially in the large scale data era, what are the advances of kernel methods? What is the difference between kernel methods and multiple instance learning?
If th... | g59928 | [
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<p>I have two matrices which each represent the distribution of a different variable on the same spatial domain (something like the distribution of cows on a field on one day versus the distribution of horses on the same field on a different day), and I'd like to check whether these matrices are correlated. I've been s... | g59929 | [
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<p>I have a sort of philosophical question about when multiple comparison correction is necessary.</p>
<p>I am measuring a continuous time varying signal (at discrete time points). Seperate events take place from time to time and I would like to establish if these events have a significant effect on the measured signa... | g59930 | [
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<p>I'm reading the example of the book: "S-PLUS (and R) Manual to Accompany Agresti’s Categorical Data Analysis (2002) 2nd edition " (page 55) and when I try to reproduce the example I get this:</p>
<pre><code>snoring<-c(0,2,4,5)
logit.irls<-glm(cbind(yes=c(24,35,21,30), no=c(1355,603,192,224))~snoring,
famil... | g15757 | [
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<p>I am using libsvm (which is meant for solving binary classification problems) for multi-class classification. How can I get classification scores / confidences for each class to effectively compare them given that libsvm can only produces scores for two classes. Desired output:</p>
<pre><code>Class 1: score1
Class... | g59931 | [
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<p>This is for a friend of mine. As an econometrician used to rely on large samples for inference, I find myself unsure whether the answer I have in mind is the best.</p>
<p>Suppose we have four continuous random variables, X, Y, W and Z. We have a small (5 to 10 observations) iid sample from each.</p>
<p>We want to ... | g15762 | [
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<p>I need to find the minimum of a function. Reading the docs at <a href="http://docs.scipy.org/doc/scipy/reference/optimize.html">http://docs.scipy.org/doc/scipy/reference/optimize.html</a> I see that there are several algorithms that do the same thing, i.e. find the minimum. How do I know which one I should choose?</... | g59932 | [
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<p>I know Bayesian or Directed Graphical models are good for fast inference using message passing techniques. But how does it work with undirected models? With directed models, you moralize the graph making it an undirected and triangular graph whose cliques are connected in a junction tree thus allowing the message pa... | g59933 | [
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<p>I have a dataset:</p>
<ul>
<li>X variable is date (from April to October)</li>
<li>Y variable is vegetation biomass data</li>
</ul>
<p>In my study area, growing season starts around April when vegetation biomass is low and peaks around at the end of August when biomass is highest, and finishes around October. </... | g59934 | [
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<p>Feature or bug? Why is it that the tick marker for zero projects is <strong><em>after</em></strong> the bar that represents the count for zero in this plot (instead of being in the middle as I'd have expected):</p>
<pre><code>> qplot(projects,data=subset(df,projects<1000),geom="bar")
stat_bin: binwidth defau... | g15765 | [
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<p>I'm still learning logistic regression, so hopefully my question makes sense. I have 10 independent variables and one dependent. The dependent and 3 of the independent variables are dichotomous (with no=0 and yes=1). The other independent variables all have a comparison of 0 and 3 options.</p>
<p>When I go to analy... | g49516 | [
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<p>I have two (unpaired) distributions. The distributions are far from being normal, so I'm using the Wilcoxon test to compare their medians: the Wilcoxon test does not reject the null-hypothesis (p-value = 0.5584). Then I'm comparing variances of these distributions using the Siegel-Tukey test, which turns out to reje... | g59935 | [
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<p>I was wondering how finance folks go about storing and modelling portfolio exposure relationships with the aim to later aggregate or slice & dice the exposures by different factor sets.</p>
<p>For example, a portfolio invests into changing set of instruments (stocks, bonds, other portfolios ...) with time-vary... | g59936 | [
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<p>What are the most widely used measures of predictive power of attributes in scoring models?</p>
<p><strong>Motivation</strong>: I have a lot of attributes, more than I can study by myself and I want to select somehow the most promising ones. Is IV a good criterion for that? Are there any alternatives?</p> | g59937 | [
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<p>I've described a typical design for my experiments <a href="http://stats.stackexchange.com/questions/11887/is-this-design-a-one-way-repeated-measures-anova-or-not">in this question</a>. Well, 1-way RM ANOVA assumes a Gaussian distributed vector.<br>
I try $y=\arcsin{\sqrt{x}}$. But for some data it works, for some d... | g59938 | [
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<p>I have generated 100 2D correlated MVN variables in R, on which I run <code>prcomp</code>. When I plot the projected points along the first principal component (in the original coordinates) with the original data overlaid, I have a bunch of points along a line (as expected) yet they do not seem to correspond to the ... | g59939 | [
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<p>I'm pretty much stuck on part (ii). Any guidance would be appreciated!</p>
<p>The Dirac measure $\delta_{x_0}$ for $x_0$∈$\mathbf{R}$ is defined over the measurable space $\left(\mathbf{R}, \mathbf{B}\right)$ by:</p>
<p>$\begin{equation}
\delta_{x_0}(B)=\begin{cases}
1, & \text{if $x\in B$}.\\
0, &a... | g59940 | [
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<p>F-tests can be <strong>two-tailed</strong> (to test that $s_1^2 \ne s_2^2$) or <strong>one-tailed</strong> (to test that $s_1^2 > s_2^2$).</p>
<p>How can I modify Levene/Brown-Forsythe to be "one-tailed", that is, to test $s_1^2 > s_2^2$ instead of $s_1^2 \ne s_2^2$?</p>
<p>Here is a demo:</p>
<p><img src="... | g15770 | [
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<p>I'm in charge of contacting customers of a company in order to analyse their satisfaction.</p>
<p>The problem is I contact them by phone and the people I contact (the sample) are not representative of the full population.</p>
<p>Then I consider post-stratification but the problem is I need to ensure the new versio... | g59941 | [
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<p>Could you give me a good link where the concept of concavity of the log likelihood related to hidden markov model EM algorithm is clarified? Thank you in advance.</p> | g59942 | [
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<p>I'm working through a Power-Point presentation about extreme value theory with application to finance. My question is about a technique to calculate the confidence interval of a $k$ $n$-block return level $R_{n,k}$.</p>
<p>Suppose we have divided our data in $m$ blocks, each block of size $n$. We denote with $M^i_n... | g18582 | [
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<p>have a normal distribution. I would like to compare two input probabilities from this population to measure how "similar" they are. Everything is subjective but I wanted to be able to say that $x$ is more "similar" to $y$ than $z$ to $y$, using some sort of an equation against the normal distribution.</p>
<p>For ex... | g59943 | [
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<p>Whenever I read about repeated measures or within-subjects design in different books and on webpages, the example that always is brought up is some kind of longitudinal or repeated measures design (e.g. people are measured on the same scale several times during the day). For my experiment, I have showed people a num... | g59944 | [
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<p>I am hoping to understand best way to test statistical significance between 2 dependent population groups. </p>
<p>For example, consider a usability test. When 100 subjects were tested, 50 of them clicked (=50% click rate). However, 50 of the subjects were male, 40 of whom clicked for an 80% click rate for males.</... | g59945 | [
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<p>I've seen examples of constructing multivariate distribution with univariate marginals coupled together via a normal copula (see <a href="http://cran.cermin.lipi.go.id/web/packages/copula/copula.pdf" rel="nofollow"> Mvdc </a> function from <code>copula</code> package in R). However I was wondering whether I could si... | g15775 | [
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<p>Precision Tool Company owns a five-year-old truck. After careful consideration, management has decided that there is a one in five chance that the truck will have to have major repairs within the next year. The odds are 3 to 2 that it will require minor repair. If major repairs are necessary, there is a 0.75 probabi... | g59946 | [
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<p>Well hello,</p>
<p>this is my first question in CrossValidated. I hope I am in the right place.
I am trying to make libLinear work. I am using the interface of matlab but it does not functions normally. To be more specific I have a dataset with multiple labels and so I tries to solved it by constructing multiple bi... | g59947 | [
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<p>I have a dependent variable which is measured in two different areas (DV1,DV2). I want to see if the relationship my independent variable (IV) has with each DV is transferable to the other DV i.e. if we know the relationship between DV1 and IV, can this be used to successfully predict DV2, and vice versa.</p>
<p>P... | g15776 | [
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<p>I'm implementing a non-linear SVM classifier with RBF kernel. I was told that the only difference from a normal SVM was that I had to simply replace the dot product with a kernel function:
$$
K(x_i,x_j)=\exp\left(-\frac{||x_i-x_j||^2}{2\sigma^2}\right)
$$
I know how a normal linear SVM works, that is, after solving... | g59948 | [
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<p>Consider the stationary VAR process</p>
<p>$${\bf X}_t = \sum_{\tau = 1}^{L} A_\tau {\bf X}_{t-\tau} +{\bf \epsilon}_t$$</p>
<p>If the innovations $\epsilon_t \sim MVN({\bf 0},\Sigma)$ then is ${\bf X}_t$ a Gaussian stationary process? </p>
<p>Is it correct that due to the invertibility of the VAR into an MA and ... | g59949 | [
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<p>For Data Stream Mining, especially in Document Classification, the most common ML algorithms are Multinomial Naive Bayes, Stochastic Gradient Descent and Ozbag (ADWIN).
When looking at their ageing behavior, they either assign same weights to all data points (Landmark Window) or "forget" older data points (Sliding W... | g59950 | [
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<p>Can we write an equation for </p>
<p><strong>P(R|S) = ?</strong></p>
<p><img src="http://i.stack.imgur.com/41Dg3.png" alt="enter image description here"></p>
<p>If you refer to a document it will be great.</p> | g59951 | [
-0.0022481377236545086,
-0.00407688831910491,
-0.0359908826649189,
0.0092043811455369,
0.020023932680487633,
-0.04960013926029205,
-0.03059166669845581,
0.04356822744011879,
-0.05430370569229126,
0.0034567287657409906,
-0.04818571358919144,
0.06577533483505249,
0.047661084681749344,
-0.027... |
<p>Let $B(t)$ be Brownian motion. Show that $e^{-\alpha t}B(e^{2\alpha t})$ is a
Gaussian process. Find its mean and covariance functions.</p>
<p>thanks .</p> | g3125 | [
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0.034250810742378235,
0.039518967270851135,
... |
<p>If I have a set of samples, say 100-200 samples and I'd like to create the distribution model from this list of samples, what is a reasonably efficient way of doing it? Are there any opensource / easily accessible statistical libraries?</p>
<p>eg: if I <em>assume</em> it's a normal distribution, I can easily find t... | g59952 | [
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0... |
<p>I have created an ARX-model where I predict the nitrogen oxide levels based on past values of nitrogen oxide with past exogenous input values nitrogen dioxide, temperature, atmospheric particulate matter, etc.</p>
<p>This might be a straightforward question, but I started to wonder if for example my ARX-model would... | g59953 | [
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0... |
<p>In presentations of k-means to compute the centroid of a new cluster the Euclidean average seems to always be used. If the similarity metric used is not the Euclidean metric it seems to me this other metric should be used to determine the centroid.</p>
<p>So my questions are:</p>
<p>1) what results are there that... | g49575 | [
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<p>I want to build a regression model to predict daily income from customers. I have 2 problems:
1. Choosing data for the training set - do I use daily income from 1 month ago, 6 month ago etc.
2. How do I validate the model - I can use the model to predict the income from the customer on the first day, the second day ... | g59954 | [
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<p>I have a learning problem from $X$ to $Y$ where:</p>
<ul>
<li>$X$ = $n$ input numeric vectors of $m$ dimensions </li>
<li>$Y$ = $n$ output numeric vectors of $k$ dimensions</li>
</ul>
<p>In other words:</p>
<p> <img src="http://i.stack.imgur.com/rgcru.png" alt="enter image description here"></... | g59955 | [
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0.031838878989219666,
0.018087653443217278,
0.07301047444343567,
... |
<p>We have the standard linear multivariate regression model
$y=\beta_0+\beta_1x_1+\beta_2x_2+u$ under the Gauss-Markov assumptions.
Suppose we estimate $\gamma_0, \gamma_1, \gamma_2$ from $x_2=\gamma_0+\gamma_1x_1+\gamma_2y+v$ and get $\hat{\gamma_0}, \hat{\gamma_1}, \hat{\gamma_2}$. Is $\frac{1}{\hat{\gamma_2}}$ an u... | g45136 | [
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0.0... |
<p>I have 6 subjects. For each subject, we measured two variables over six-week period once a week. Let’s call the variables A and B. Variable A is binary (male or female), and variable B is continuous (blood pressure). Now I want to see if females have higher blood pressure than males. What kind of statistical method ... | g49819 | [
0.0495646670460701,
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0.019155772402882576,
0.055659450590610504,
0.0038435054011642933,
... |
<p>I have a linear regression model with some correlated errors: $Y_t=\beta_0+\beta_1X_1+\beta_2X_2+\epsilon_t$, where $\epsilon_t$ is a AR(1) i.e. $\epsilon_t=\phi\epsilon_{t-1}+\nu_t$ with $\nu_t$ as white noise terms. I want to obtain the joint maximum likelihood estimates of $\beta_j$'s for $j=0,1,2$ and $\phi$ as ... | g41224 | [
0.010764893144369125,
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0.000516570988111198,
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0.0337029... |
<p>I am a computer scientist performing research, which includes calculating the Spearman rank correlation of two lists, one ranked by a human, another by a computer program.</p>
<p>I have the following questions:</p>
<p><ol>
<li>I was reading this <a href="http://stats.stackexchange.com/questions/18887/how-to-calcul... | g15553 | [
0.035061582922935486,
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0.005279571283608675,
0.04841695353388786,
-0.0011524349683895707,
0.002... |
<p>Is there a way to know that? Is this a good stackexchange to ask?</p>
<p>Basically I am looking at the number of children within marriage whose biological dad is not the mother's husband during conception.</p> | g59956 | [
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<p>I'm trying to predict the number of vehicles per model required to maximise utilisation and booking volume but I've hit a brick wall.</p>
<p>I've done some exploratory analysis and utilisation is affected by booking days. Also booking days is affected by booking length and bookings per car. </p>
<p>I've worked out... | g59957 | [
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0.0017386735416948795,
0.005429685581475496,
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0.05923531576991081,
0.04... |
<p>i got a question regarding random slopes in hierarchical models (multilevel).
I fit two models:</p>
<p>Model 1: without random slope for covariate x (only random intercept)</p>
<p>Model 2: random slope for covariate x</p>
<p>When adding the random slope (Model 2) for x the fixed effect for covariate x gets insign... | g15790 | [
0.02961999550461769,
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0.03373657539486885,
0.009013770148158073,
0.04... |
<p>I have the following data set of a two-wave longitudinal study in educational psychology. A group of 400 people did some questionnaire on IQ, personality and two different emotional states (sadness and melancholy) at time 1 and one year later at time 2. </p>
<p>My hypotheses are: </p>
<ul>
<li>IQ is a significant... | g282 | [
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0.0071184164844453335,
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<p>I have developed a technique to count bacteria on a petri dish. Previously these bacteria could not be counted, so there is no reference standerd to compare our measurements with. To show the preciseness of my method I thought it was a good idea to do replicated measurements. </p>
<p>Therefor I measured the same 20... | g15793 | [
0.03124300390481949,
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0.03444669395685196,
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0.0417... |
<p>I have a joint distribution which factorises as follows:</p>
<p>$$
q(w) = \prod_{i=1}^{N} t_i
$$</p>
<p>where each $t_i$ is a 3-dimensional normal distribution which some mean $\mu_i$ and variance $\mathbf{I}\sigma_i$ where $I$ is the identity and $\sigma_i$ is the precision which is also three dimensional to have... | g59958 | [
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0.0508919321000576,
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-... |
<p>I am using multiple imputation to impute a continuous variable ($X$) with $\approx30\%$ missing values. I have a question regarding the generation of a new categorical variable ($Y$), starting from this imputed variable.</p>
<p>I want to use $Y$ as an independent variable in a logistic regression model instead of $... | g59959 | [
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0.014002295210957527,
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0.009017755277454853,
0.003772465977817774,
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... |
<p>Is logistic regression an appropriate classifier when the input data are binary? Say we are conducting an experiment where the subject is presented with blue and green circles of varying shades, and asked to pick the blue one in each trial. We have 10 controls and 10 cases who are presumed to be blue-green color bli... | g59960 | [
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<p>I would like to get an analytical expression for
$$\mathbb{E}\left(\frac{\sin(aX)}{aX}\frac{\sin(bY)}{bY}\right)$$
or at least an analytical approximation thereof, when $a,b$ are positive reals, and</p>
<p>$$\begin{pmatrix}X\\Y\end{pmatrix} \sim \mathcal{N}(\mu,\Sigma) $$
where</p>
<p>$$\mu \equiv \begin{pmatrix}x... | g59961 | [
0.03339337557554245,
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-0.00030976079870015383,
0.015043973922729492,
0.05962533503770828,
0.019790073856711388,
... |
<p>I am reading the paper <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.4.8909&rep=rep1&type=pdf" rel="nofollow">"Star Coordinates: A Multidimensional Visualization Technique with Uniform Treatment of Dimensions"</a> and trying to plot my data.</p>
<p>Lets say I have $A(2,5,3,1,8)$, a five ... | g59962 | [
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0.008370579220354557,
0.0050340997986495495,
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0.0027349754236638546,
0.011178098618984222,
0.028501981869339943,
0.05378001928329468,
-0... |
<p>I have a two-way factorial design, with factors treatment (A vs. B) and time (T1 vs. T2). The same subject was measured twice, at T1 and T2, so I have repeated measurements. I am interested to see whether there is interaction between treatment and time on the response variable $x$.
I am applying a t-test. $H_0$ is:... | g15796 | [
0.010150525718927383,
-0.012063554488122463,
0.0014510394539684057,
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0.0521123968064785,
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0.0007161946850828826,
0.023434283211827278,
0.003568278392776847,
0.03592660650610924,
0... |
<p>Suppose I have a random variable X that either evaluates to A, B, or C when I realize it (each with its own fixed probability). Now let's say I have drawn 100 samples and the frequency distribution is something like </p>
<pre><code>A 30
B 55
C 15
</code></pre>
<p>dividing by n=100 gives me the probabil... | g26036 | [
0.052277278155088425,
0.00999458972364664,
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0.01827559620141983,
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0.02849404141306877,
0.05753384158015251,
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0.004670159425586462,
-0.0113... |
<p>I want to identify random data by applying some tests to the observed byte stream. I used the chi square test already on a frequency analysis, which works fine. To reduce the false-positive rate I want to apply some more tests, like the runs test, which checks for monotonous sequences in the byte sequence (not the r... | g15800 | [
0.005973240826278925,
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0.016846923157572746,
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0.018641110509634018,
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0.03444185107946396,
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-0.012371296994388103,
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0.04666166007518768,
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... |
<p>I am using <a href="http://en.wikipedia.org/wiki/RapidMiner" rel="nofollow">RapidMiner</a> to perform linear regression with ridge parameter 1$\text{E}$ -8, min tolerance 0.05 and M5 prime for feature elimination. The <code>std coefficient</code> parameters appear to be excessively high. What are some possible cause... | g59963 | [
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0.03026982955634594,
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0.037581343203783035,
0.011375617235898972,
0.01... |
<p>I have a Poisson model which I use on a medical data set with 329 observations. In the regression I am particularly interested in the simple Wald statistic for a single coefficient:
$$t = \frac{\widehat{\beta} - \beta}{s.e.(\widehat{\beta})}$$
I was told that simply using the robust option will not help and it was s... | g134 | [
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0.026583630591630936,
0.004504472482949495,
0.07697746902704239,
-0.0032... |
<p>Say we have TWO tests for cancer. Each test has the same probabilities of being right/wrong for cancer/no cancer. What is the probability of getting two positive test results?</p>
<p>In what follows, I'll use C for "has cancer", "+" for a positive test result, "++" for two positives (I don't distinguish between the... | g324 | [
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0.04300154000520706,
0.026819199323654175,
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0.00997... |
<p>Assume that X depicts a random variable denoting the time it takes someone to sweep the floor today and Y be the time it takes him tomorrow and Z be the time it takes him on the last day of October.</p>
<ol>
<li><p>If X, Y and Z are assumed to be independent, it means that the person does not "learn" how to sweep f... | g45169 | [
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0.043... |
<p>There is a fairly common theorem, which states that:</p>
<p>The sum of $n$ independent variables following an exponential distribution $\mathrm{Exp}(\alpha)$ follow an gamma distribution $\mathrm{Gamma} (n, 1/\alpha)$ (also known as Erlang distribution).</p>
<p>I'm using this theorem in my thesis. I've been asked... | g17222 | [
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0.01935684308409691,
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0.013408416882157326,
0.02278958074748516,
... |
<p>I have a train file which has categorical features like</p>
<pre><code>IN JJ PRP_VBP
VB NN PRP$
. . .
</code></pre>
<p>The third column is the ground truth and can have value only out of {PRP_VBP, PRP$}. The first two columns can have value from 36 such tags. Now I have to train some model and then predict the... | g59964 | [
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0.014038965106010437,
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<p>I'm wondering what should be the optimal sampling strategy for my dissertation research. I have four data sources (two open source software projects meta-repositories and two global startup databases). I'd like to perform EFA to discover (or, rather, confirm my theory-based assumptions) the factor structure of the s... | g59965 | [
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0.042450692504644394,
0.0453491248190403,
-0.027560235932469368,
0.03791150078177452,
-0... |
<p>Assume that I'm going to estimate a linear regression where I assume $u\sim N(0,\sigma^2)$. What is the benefit of OLS against ML estimation? I know that we need to know a distribution of $u$ when we use ML Methods, but since I assume $u\sim N(0,\sigma^2)$ whether I use ML or OLS this point seems to be irrelevant. T... | g45176 | [
0.008165489882230759,
-0.039800457656383514,
0.02441512607038021,
-0.03230606019496918,
0.012111453339457512,
-0.031954266130924225,
0.023609332740306854,
0.03442887216806412,
-0.027471277862787247,
-0.03440748155117035,
-0.021408723667263985,
0.0454583466053009,
0.04160625860095024,
0.013... |
<p>I have two corpora for example, each of which contains a set of different documents, and each document are already represented as a vector of words in a certain way. The two corpora are small, only contains 20 documents or so. So How can I calculate the similarity between the two corpora? Any good ideas?</p>
<p>I t... | g59966 | [
0.036245252937078476,
-0.009818971157073975,
0.0019150173757225275,
-0.054255444556474686,
-0.03551911935210228,
-0.021250424906611443,
-0.008310451172292233,
-0.02272973209619522,
-0.08486606925725937,
0.025722309947013855,
0.006632491946220398,
-0.008580135181546211,
0.02097795158624649,
... |
<p>I have a continuous distribution whose PDF I know the expression for but whose CDF is difficult to compute analytically. I understand that if I know the CDF value, then I can use inverse transform sampling to sample from the distribution. This would involve drawing from a uniform(0, 1) distribution, finding the corr... | g59967 | [
-0.015398373827338219,
-0.017107591032981873,
-0.007983570918440819,
-0.07769870012998581,
-0.05771484971046448,
-0.022267386317253113,
-0.032563626766204834,
0.054277390241622925,
-0.04843197762966156,
0.010163236409425735,
-0.011668394319713116,
-0.005386931821703911,
0.08535195887088776,
... |
<p>I'm currently trying to predict the probability for low probability events (~1%).
I have large DB with ~200,000 vectors (~2000 plus examples) with ~200 features.
I'm trying to find the the best features for my problem. What are the recommended method? (preferred in Python or R, but not necessarily)</p>
<p>Thanks!<... | g59968 | [
0.039524976164102554,
-0.0052167861722409725,
0.016744479537010193,
-0.010220581665635109,
-0.058175478130578995,
-0.08204690366983414,
0.04577089101076126,
0.045202892273664474,
-0.02159384824335575,
-0.07658159732818604,
-0.0017751019913703203,
0.013114425353705883,
0.05124009773135185,
... |
<p>I am using SAS to estimate some logistic models. Usually, I work with either MDs or social scientists, and odds ratios are the preferred metric. But I am now working with a client in economics/law and she wants the marginal effects and their standard errors, and she wants them at the means of the other variables.</p... | g59969 | [
0.029202569276094437,
-0.04488420486450195,
-0.008567554876208305,
-0.022921103984117508,
-0.04146086797118187,
-0.018291331827640533,
-0.028665827587246895,
-0.02522825263440609,
-0.0720164105296135,
-0.07038357108831406,
0.013656392693519592,
0.019929107278585434,
0.04135141894221306,
-0... |
<p>I've have a script that creates Weibull distributions with a static shape parameter and a variable scale parameter, the scale parameter changing to yield a distribution that meets a specified mean while maintaining the shape parameter.</p>
<p>I have calculated that the standard deviation for my distributions always... | g59970 | [
-0.02746337652206421,
-0.008435668423771858,
-0.01726563461124897,
-0.02033592015504837,
-0.04908803477883339,
-0.010151918977499008,
0.029982957988977432,
0.0163539107888937,
-0.033597130328416824,
0.014121378771960735,
-0.018248585984110832,
-0.0478634238243103,
0.03307642042636871,
0.03... |
<p>Lots of people use cluster analysis. I've heard very few explicitly say why. I imagine this is because within a given field, most researchers seem to understand why clustering is used for the problems typical to that area - but uses vary between fields, and I haven't seen those differences addressed anywhere. </p>
... | g15808 | [
0.0399160236120224,
-0.03603222593665123,
0.033754970878362656,
-0.024098433554172516,
0.00543515058234334,
-0.06815982609987259,
0.007700636982917786,
0.031101930886507034,
-0.011622365564107895,
-0.028621071949601173,
0.048328377306461334,
-0.038935862481594086,
0.10164400190114975,
0.02... |
<p>I'm calculating elasticity right now for alternative-specific conditional logit asclogit model.</p>
<p>Stata does not have any command or menu for elasticity calculation. I used the popular formula: (1-p)(beta)(X) for direct elasticity. But for cross elasticity is different. provided formula is: -p(i)p(j).beta wher... | g59971 | [
0.006752102170139551,
0.019466830417513847,
-0.030821150168776512,
-0.05713663622736931,
-0.0006071822135709226,
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0.03513054549694061,
-0.01893782615661621,
-0.029800739139318466,
-0.011462283320724964,
-0.02017396315932274,
-0.021046161651611328,
0.07015915215015411,
... |
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