question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I have fit two generalized estimating equation (GEE) models to my data:</p>
<p>1) Model 1: Outcome is longitudinal Yes/No variable (A) (year 1,2,3,4,5) with longitudinal continuous predictor (B) for years 1,2,3,4,5. </p>
<p>2) Model 2: Outcome is the same longitudinal Yes/No variable (A), but now with my predictor... | g15457 | [
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<p>I am using a cox proportional hazards model to run a survival analysis in r on a number of non-nested, distinct covariates such as Age, Blood Type, Cancer, etc: </p>
<pre><code> A, B, C, D, E
</code></pre>
<p>When I run the model on the omnibus null hypothesis:</p>
<pre><code>surv ~ A + B + C + D
</code>... | g59730 | [
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<p>I completed a Monte Carlo simulation that consisted of one million ($10^6$) individual simulations. The simulation returns a variable, $p$, that can be either 1 or 0. I then weight the simulations based on predefined criteria and calculate the probability of $p$. I also calculate a risk ratio using $p$:</p>
<p>$$\t... | g59731 | [
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<p>I am looking into making a regression of a bunch of data that is contained on some range of real numbers. In my case, x is between 0 and 1 and y is between 0 and 10. If I have 150 data points on this plane, and want to best model the original data with N data points (not polynomial, just points), how can I do this? ... | g59732 | [
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<p>For 1,000,000 observations, I observed a discrete event, X, 3 times for the control group and 10 times for the test group. How do I determine for a large number of observations (1,000,000), if three is statistically different than ten?</p> | g15460 | [
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<p>I can't find literature to understand this table.
What I know doing my research is that an effect size should be between 0 and 1. when 0.2 is slow, 0,5 medium and 0.8 and higher , high. But In an article of Cochrane database I found these results and I can't really make a sense of this. I need this really badly so ... | g59733 | [
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<p>I am trying to run a regression using about 80 independent variables. The problem is that the last 20+ coefficients return NA. If I condense the range of data to within 60, I get coefficients for everything just fine. Why am I getting these NAs and how do I resolve it? I need to reproduce this code using all of thes... | g15462 | [
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<p>What are some podcasts related to statistical analysis? I've found some audio recordings of college lectures on ITunes U, but I'm not aware of any statistical podcasts. The closest thing I'm aware of is an operations research podcast <a href="http://www.scienceofbetter.org/podcast/">The Science of Better</a>. It ... | g59734 | [
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<p>We have two cohorts of 1000 samples each. We measure 2 quantities on each cohort. The first one is a binary variable. The second is a real number that follows a heavy tail distribution. We want to assess which cohort performs best for each metric. There are plenty of statistical tests to choose from: people suggest ... | g59735 | [
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<p>I have 3 features of a signal (example: amplitude, frequency, energy). I want to check which feature is the best to represent that particular signal. That signal is classified into two categories (good or bad). I used ROC to find the AUC. From my understanding: the bigger the AUC is the better it can discriminate be... | g59736 | [
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<p>I am trying to use Hierarchical clustering to see how well it performs in classifying a dataset which I previously know its true classification. I am new to clustering in general. I was able to draw the dendogram of the cluster, but I am not sure how I can measure the performance of this method. Here's a reproducibl... | g59737 | [
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<p>To set the scene -
i am using neural nets in SAS program
i have ~ 1000 points
variables have been selected prior to this on a combination of human knowledge and variable recombination (PCA etc)
I am using 3 way 60-20-20 validation and 70-15-15</p>
<p>I have come up with a method that im sure has a flaw somewhere a... | g15466 | [
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<p>Can you correlate 2 Likert scales when the question for each one was different?</p>
<p>I have 1 question which asks how concerned someone is about pollution. They rank this on a Likert Scale of 1-5 where 1 is most concerned and 5 not at all.</p>
<p>Then my other question asks whether people intend to take any extr... | g59738 | [
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<p>Based on UK's Framework for Marine and Esuarine Model Specification,the % RMSE for current speed is calculated by dividing RMS by maximum peak current. </p>
<p>$$\text{RMSE(%)} = \left(\frac{\text{RMSE}}{\text{Max current speed}}\right) \cdot100$$</p>
<p>Why maximum peak current is used and not mean average? </p>
... | g59739 | [
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<p>I'm looking for examples of surrogate loss functions that are useful for binary-class classification but are not consistent with respect to the zero-one loss, where I'm using consistency in the sense of surrogate loss functions converging to Bayes predictor [1] (also known as classification calibration, Bayes consis... | g15468 | [
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<p>I'm doing survival analysis with time dependent covariates, using the counting process style. I already have a set of models and I want to test de residuals.
I'm having trouble with the lack of information about this subject, <strong>it makes sense to test Schoenfield residuals for time-dependent covariates</strong>... | g59740 | [
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<p>I have satellite data that provides radiance which I use to compute the Flux (using surface and cloud info). Now using a regression method, I can develop a mathematical model directly relating radiance and flux and can be used to predict the flux for new radiance values.</p>
<p>Is it possible to do same using decis... | g59741 | [
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<p>The definition of the probability density function of the continuous uniform distribution <a href="http://en.wikipedia.org/wiki/Uniform_distribution_%28continuous%29#Probability_density_function" rel="nofollow">on Wikipedia</a> is:</p>
<p>$$
f(x) = \left\{
\begin{array}{}
\frac{1}{b-a} & \text{f... | g59742 | [
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<p>Let's suppose there is a project which is expected to take a certain amount of time to complete. As certain jobs are done, we can quantifiably measure how much of the project has been completed at any time. </p>
<p>Consider a progress bar - it starts at 0%, and is updated at some discrete time values as parts of th... | g15472 | [
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<p>I imagine that the larger a coefficient on a variable is, the more ability the model has to "swing" in that dimension, providing an increased opportunity to fit noise. Although I think I've got a reasonable sense of the relationship between the variance in the model and large coefficients, I don't have as good a sen... | g59743 | [
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<p>I'm working with the Nataf Transformation (i.e a Gaussian copula) and am looking at bivariate joint distributions. However I can't find any publications discussing the limitations of the transform. For example it seems that some joint distributions cannot be completely describe by the transform and I'm trying to fin... | g15479 | [
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<p>I ran into a problem analysing some data I produced. I measured concentrations in biological samples in a time course manner. I measured three replicates for each of the seven time points. I can display the data as means +- SD, that's easy. </p>
<p>Now I want to express the data as percent changes relative to the f... | g59744 | [
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<p>I have monthly water quality (Nitrate) measurements from July, 2005 till Oct., 2013 (84 measurements). However, there is no measurements from Oct., 2007 till June, 2009 (21 measurements). Could you please let me know how do I fill in the missing data using other dataset? What is the best software do you recommend to... | g15482 | [
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<p>I'm trying to fit a spline for a GLM using R. Once I fit the spline, I want to be able to take my resulting model and create a modeling file in an Excel workbook. </p>
<p>For example, let's say I have a data set where y is a random function of x and the slope changes abruptly at a specific point (in this case @ ... | g59745 | [
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<p>Could you explain to me how the shape of a ROC curve is determined?</p>
<p>From the following illustration, it seems that for every time the actual class (C) is positive, it goes up and when it's negative, it goes to the right.</p>
<p>Why does it only seem to be based on the true class rather than the actual right... | g59746 | [
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<p>What can be said about the convergence rate of stratified sample means to a normal distribution, given different allocation schemes? Obviously, under very poor allocation, this convergence can fail (for instance, keeping the sample size in one stratum fixed); but for any reasonable scheme, and under reasonable hypot... | g59747 | [
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<p>I don't understand how the LM statistic works because if we run the regression and then record the residual, and then run the regression using the residual as the dependent variable and then using the unrestricted model, how can we run a regression of a constant on 5 different variables? For example, I'm using Stata... | g626 | [
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<p>I measured a binary response for each subject in 5 different conditions. For each subject and condition, I replicated the experiment 36 times. I thus have 36 binary values per condition per subject.</p>
<p>I am trying to build a model for those data. I suppose a logistic regression is what I'm looking for, and I am... | g59748 | [
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<p>I have a question about mean value in a Likert scale.</p>
<p>My objective is to identify important factors for selecting short or long term relationship with subcontractor.</p>
<p>I used Likert-type scale ranging from "highly agree" to "highly disagree" on 22 factors.
Then I have asked 41 main contractors and I us... | g15486 | [
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<p>If the interest is merely estimating the parameters of a model (pointwise and/or interval estimation) and the prior information is not reliable, weak, (I know this is a bit vague but I am trying to establish an scenario where the choice of a prior is difficult) ... Why would someone choose to use the Bayesian approa... | g15487 | [
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<p>I have a case study where a company made new golf balls with stronger coatings than current golf balls. One of the technicians is concerned that the new coating may decrease the driving distance. An experiment was conducted in which 40 types of each ball was hit by a machine to determine mean driving distance of the... | g59749 | [
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<p>I am working on a problem which requires one-class classifier. I am using LIBSVM. I know there are tons of material out there but still I could not find the answer to my query.</p>
<ol>
<li><p>How do I estimate the optimum parameters for the RBF kernel?</p></li>
<li><p>Using <code>svm-train -s 2 -t 2 -v 5 train.sca... | g59750 | [
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... |
<p>Let $U_1, \ldots, U_n$ be $n$ i.i.d discrete uniform random variables on (0,1) and their order statistics be $U_{(1)}, \ldots, U_{(n)}$.</p>
<p>Define $D_i=U_{(i)}-U_{(i-1)}$ for $i=1, \ldots, n$ with $U_0=0$. </p>
<p>I am trying to figure out the joint distribution of $U_i$'s and their marginal distribution and p... | g59751 | [
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<p>I've written some Python code which does some (network) data analysis. It's mostly large data coming from SQL where I play around with statistics and algorithms.</p>
<p>However configuring the interplay between modules and tracking/debugging what's going on with the data isn't very convenient.
Do you know a tool wh... | g59752 | [
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0.0... |
<p>I have been using Latent Dirichlet Analysis for a while but I am a bit confounded as to it's practical ability to compare two documents. It is of course ideal for classification when you want to see in what category a certain document or word belongs, but in content comparison I am at my wits end.</p>
<p>An inferre... | g59753 | [
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<p>I've been fitting some time series data using a Poisson general additive model using SAS's <code>PROC GAM</code>. Generally speaking, I've been having it's built-in generalized cross-validation procedure generate at least a decent "starting point" for my single spline, which is a non-linear function of time along wi... | g15491 | [
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<p>I'm trying to implement a regression model with both fixed and random effects. The package I use is the <code>lme4</code>.</p>
<p>I want to find the relationship between the continuous variables <code>X1</code> and <code>X2</code>, using the categorical variable <code>F1</code> as a fixed effect.</p>
<p>When I try... | g59754 | [
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0.... |
<p>I am not particularly familiar with statistics and am looking at methods for analysing numbers that have been broken into different "brackets" or "groups" for different entities.</p>
<p>Consider three companies. </p>
<ul>
<li><p>A announces that they have 10 factories generating between 10,000 and 20,000 widgets p... | g59755 | [
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... |
<p>I'm doing this project where we are investigating whether social networks can influence peoples distinctiveness. Briefly summarized, we have primed a group with a social media and another is the control group. Afterwards, they were given a questionnarie where they have...</p>
<ol>
<li>Written 12 identity elements 2... | g37882 | [
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0.04114631563425064,
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0.033... |
<p>If I have a logistic regression equation in the form of : </p>
<p>Logit($\pi$($X_1$, $X_2$)) = $\beta_0$ + $\beta_1$$X_1$ + $\beta_2$$X_2$ + $\beta_3$$X_1$$X_2$</p>
<p>where $X_1$ and $X_2$ are both binary categorical variables and there is an empty cell in their contingency table, what happens to $\beta_3$?</p>
... | g15496 | [
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<p>My data looks like this (F=Features)</p>
<pre><code> F1 F2 F3 F4 F5 F6 F7 F8....
ID1 0.67 0.76 0.3 0.54 0.21 0.88 0.97 0.45....
ID2 0.76 0.68 0.10 0.45 0.12 0.44 0.79 0.54....
ID3 0.67 0.76 0.3 0.54 0.21 0.88 0.68 0.76....
ID... | g15546 | [
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0.06901469826698303,
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<p>An English soccer team plays a series of matches against different opponents, of varying ability. A bookmaker offers odds for each match as to whether it will be a home win, away win, or draw. Part-way through the season, the team has played n matches, and has drawn $k$ of them, which is more than might be expected ... | g15499 | [
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0.0029387199319899082,
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-... |
<p>Reading the paper <em>"Distribution of Inner Product of Two Complex Gaussian Vectors and its Application to MPSK Performance" by Mallik R.K.</em> I can not get one of the steps.
<br>The author assumes two complex Gaussian vectors
$$\vec{X}\sim\mathcal{CN}(\vec{\mu_X},\mathrm{I}), \\ \vec{Y}\sim\mathcal{CN}(\vec{\mu_... | g59756 | [
0.010702522471547127,
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0.05394286662340164,
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-... |
<p>Following my question <a href="http://stats.stackexchange.com/questions/57876/heckman-sample-selection-vs-ols">Heckman sample selection vs. OLS</a> about the meaning of Mills ratio I am wondering why some researchers estimate a generalization of Heckman instead of the actual Heckman's procedure.
(based on Das et.... | g15273 | [
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0.010926113463938236,
0.04028467461466789,
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<p>The title says it.</p>
<p>If one wishes to analyze ternary outcomes—that is categorical outcomes with specifically three values (-1,0,1)—are $\chi^{2}$ / contingency table tests and multinomial-logistic regression type models the only choices for making inferences, or are there well-articulated and useful ternary d... | g15502 | [
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0.016291910782456398,
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0.03241433948278427,
... |
<p>Suppose you get to observe "matches" between buyers and sellers in a market. You also get to observe characteristics of both buyers and sellers which you would like to use to predict future matches & make recommendations to both sides of the market. </p>
<p>For simplicity, assume there are N buyers and N sel... | g49679 | [
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0.00007028183608781546,
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0.... |
<p>I have a set of values $x$ and $y$ which are theoretically related exponentially:</p>
<p>$y = ax^b$</p>
<p>One way to obtain the coefficients is by applying natural logarithms in both sides and fitting a linear model:</p>
<pre><code>> fit <- lm(log(y)~log(x))
> a <- exp(fit$coefficients[1])
> b <... | g59757 | [
0.03302014246582985,
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0.015279075130820274,
0.03363865613937378,
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0.031191712245345116,
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0.0062136841006577015,
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0.031243545934557915,
0.07094752788543701,
0.... |
<p>I've always wondered this. Let's say someone gives you a spreadsheet with a large set of numbers, say 10,000, and says "What distribution does this set of numbers follow (Gaussian, exponential, Poisson, etc.)"? How do you go about determining the answer?</p> | g15503 | [
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<p>I'm trying to compute the expected opportunity loss (EOL) for a simple investment problem, where the cost <strong><em>C</em></strong> is set to be exactly 5 million and the value <strong><em>V</em></strong> is estimated to be normally distributed between 2.5 million and 25 million (with 90% CI).</p>
<p>I understand... | g59758 | [
0.03768216073513031,
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0.014021258801221848,
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0.011564359068870544,
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0.035475827753543854,
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0.06988850235939026,
-... |
<p>Is this possible to compute?</p>
<p>From a normal distribution we took a sample $( 11, 13, 13, 14, 14, 14, 15, 15, 17, 18).$ Compute the $98 \%$ confidence interval of the expected value.</p>
<p>I'm studying statistics on my own but I don't know what formula should I use here.</p> | g59759 | [
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<p>I'm fitting linear mixed models and I have slightly inflated p-values due to multicollinearity.
I deleted the factors with the highest VIFs until none of them was larger than 3.</p>
<p>The VIFs tell me, how much the variances in my model are inflated due to collinearity, so just out of curiosity, I then calculated... | g15505 | [
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0.019271070137619972,
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0.02820463478565216,
... |
<p>I'm using approximate Bayesian computation to find the true value of a parameter. My prior distribution is uniform over $(0, 1)$. </p>
<p>I was watching <a href="http://work.caltech.edu/library/182.html" rel="nofollow">this video on Bayesian learning</a> and the lecturer states (around 36:00) that this is making a ... | g59760 | [
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0.05729... |
<p>Let $Y_1, \cdots, Y_n$ be independent random variables
each with the distribution $N(\mu, \sigma^2)$, then
\begin{align*}
S^2 &= \sum(Y_i - \overline{Y})^2 \\
&= \sum((Y_i - \mu) - (\overline{Y} - \mu))^2 \\
&= \sum((Y_i - \mu)^2 + (\overline{Y} - \mu)^2 - 2(Y_i - \mu)(\overline{Y} - \mu)) \\
&... | g59761 | [
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0... |
<p>I have a question related to using data weightings when looking at a subgroup of a population sample. I am using survey data which was provided with weights, but I only want to include the taller participants in my analysis.</p>
<p>When I have selected my subsample,the data weights obviously won't sum to 1. Can I j... | g59762 | [
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<p>I fitted ARIMA and NAR models to 10 different univariate time series. These time series are water characteristics at a water treatment plant (CO$_2$, TDS, TH, pH, ...). </p>
<p>After fitting suitable models I forecasted seven lags ahead with models for each series. I have seven observed at the end of each series th... | g59763 | [
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<p>Consider a sequence of tokens. One could fit a Markov model to this sequence by computing the empirical stochastic transition matrix.</p>
<p>A refinement to this model would be to build a HMM on top of it, with a small tweak: we let the emission probability of a token depend both on the hidden state and on the prev... | g59764 | [
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<p>This question is regarding the role of regularizer in an objective function. </p>
<p>Given a loss function $f(x)$, a regularizer function $r(x)$, and $\lambda$ being a trade-off function, our aim is to $\min f(x) + \lambda*r(x)$. I'm able to understand that as the value of $\lambda$ increases our training error in... | g37943 | [
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<p>Let $X$ & $Y$ be random vectors. Let $Z$=$f(X,Y)$ be a random variable.</p>
<p>Then if $X$ & $Y$ are independent, the following is a well known result:</p>
<p>$P(f(X,Y)\in B\mid Y=y)$ = $P(f(X,y)\in B)$</p>
<p><em><strong>I need some help to 'formalize' what appears to be an intuitive generalization when... | g59765 | [
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<p>I am referring here to the <a href="http://en.wikipedia.org/wiki/Mean-shift" rel="nofollow">Wikipedia article regarding the mean shift algorithm</a>.</p>
<p>Here the Gaussian kernel is denoted as $e^{-c\|x_i - x\|^2 }$</p>
<p>My questions are the following:</p>
<ul>
<li>Is $c$ always positive? I.e. are hence the ... | g59766 | [
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0.0... |
<p>I am about to develop a new questionnaire with 142 questions I have performed exploratory factor analysis and 30 latent factors were extracted. I was wondering if it is <strong>necessary</strong> to perform <strong>confirmatory factor analysis</strong> for my newly constructed questionnaire too.</p> | g15515 | [
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<p>(<em>This question is from my pattern recognition course.</em>) There is this exercise:</p>
<p>Imagine we have $N$ samples with $n$ dimensions. </p>
<p>First it asks to find a point $m$ where the summation of Euclidean distances from $m$ is minimum. Then imagine another vector $e$ with size of 1. $e$ passes from $... | g59767 | [
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0.04341014847159386,
0... |
<p>I have a group of items S, say there are 100 items in S, and I know some features of these items, i.e., color, size, ...Now, I have another group of items P, say there are 10000 items in P. What can I do to find a sub group of items in P that are similar to items in S? I know the corresponding features of all items ... | g59768 | [
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<p>I have a very limited understanding of statistics, and am having trouble translating <a href="http://quant.stackexchange.com/a/958/719">an answer</a> to this question from quant.SE, "<a href="http://quant.stackexchange.com/questions/955/separating-the-wheat-from-the-chaff-what-quant-methods-separate-skillful-manage"... | g15517 | [
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<p>I'm running a Metropolis sampler (C++) and want to use the previous samples to estimate the convergence rate.</p>
<p>One easy to implement diagnostic I found is the <a href="http://www2.math.su.se/matstat/reports/master/2011/rep2/report.pdf" rel="nofollow">Geweke diagnostic</a>, which computes the difference betwee... | g59769 | [
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<p>I have an AR process with t-distributed noise at each step. Does anyone know a transformation i can apply to get approximately normally distributed residuals?</p>
<p>Thanks!</p> | g59770 | [
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<p>I'm using the NLPCA to reduce the dimensionality of nine variables (4 nominal / 3 ordinal /2 numeric) to obtain the object-scores to be used as dependent variable in a regression model.
I'm using the package homals (<a href="http://www.jstatsoft.org/v31/i04/paper" rel="nofollow">http://www.jstatsoft.org/v31/i04/pape... | g44850 | [
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<p>I have recently realised that there are differences in the kurtosis values provided by SPSS and Stata.</p>
<p>See <a href="http://www.ats.ucla.edu/stat/mult_pkg/faq/general/kurtosis.htm" rel="nofollow">http://www.ats.ucla.edu/stat/mult_pkg/faq/general/kurtosis.htm</a></p>
<p>My understanding is that the interpreta... | g59771 | [
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<p>How do we find information about the distribution of a variable in presence of dependency among our observations? This dependency is coming from measuring the variable on the same group of subjects multiple times. </p>
<p>These are two examples of what I have in mind: </p>
<ol>
<li><p>Suppose we have a website fo... | g15523 | [
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<p>I have a question regarding a repeated measures experiment. I have 5 whales (randomly selected) that I recorded body temperature on. Data was collected via satellite, programmed to transmit records at 2-minute intervals, but data for each whale are not a complete time-series data set (i.e. unbalanced records/missing... | g44853 | [
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<p>I am trying to train a <code>neuralnet</code> model by using <code>caret</code> package by this command:</p>
<pre><code>model.neuralnet <- train(X, Y, method='neuralnet', trControl=myControl,
stepmax=700, rep=1, learningrate=0.05, algorithm = 'backprob',
preProcess=PP, tuneGrid = expand.grid(.layer1=4,... | g15525 | [
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<p>Thinking about probability always makes me realize how bad I am at counting...</p>
<p>Consider a sequence of $n$ base letters $A,\; T, \; C, \text{ and } G$, each equally likely to appear. What is the probability that this sequence contains a particular sequence of base pairs of interest of length $r\leq n$?</p>
<... | g15526 | [
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<p>I'm looking at 2 papers which are addressing the same issue using a retrospective cohort study design but use different methodology to analyse data and I would like to know why the methods used differ?</p>
<p>When and why would you use standardized rate ratios?</p>
<p>When and why would you use Poission regression... | g59772 | [
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<p>I'm creating a program that identifies trending music artists that uses Twitter metrics. I have data in a histogram format that represents the frequency of twitter @mentions of an artist for the last 30 days. I need my program to recognize a "significant" change (number that is quite greater than the rest in the sam... | g15527 | [
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... |
<p>It has been <a href="http://www.pnas.org/content/early/2011/08/25/1102900108" rel="nofollow">shown</a> that ABC model choice using Bayes factors is not to be recommended due to the presence of an error coming from the use of summary statistics. The conclusion in this paper relies on the study of the behaviour of a p... | g59773 | [
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0.021565813571214676,
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<p>Does someone know if it exists some way to do online learning with <a href="http://en.wikipedia.org/wiki/Probabilistic_latent_semantic_analysis" rel="nofollow">pLSA</a>? The model training is really time consuming, so it is not feasible to rebuild it after every changes in the data.</p> | g59774 | [
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<p>I have a data frame consisting of evaluations made by students of other student fellows. An excerpt of the evaluations data frame looks like this (columns are evaluators, rows correspond to the evaluated student):</p>
<pre><code> s1 s2 s3 s4
1 7 8 NA 8
2 NA ... | g37967 | [
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0.006067023612558842,
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0.0636354610323906,
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<p>in the regression model in the spss statistic software can you explain me what are the covariates variables?</p>
<p>if i want express a model like </p>
<pre><code> y = a0 + a1*x1 + ....... + an * xn
</code></pre>
<p>which are the covariates?</p> | g15529 | [
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<p>I am estimating a structural model with the following data generating process:
$$x=\begin{cases}\begin{array}{c}y-\theta\\0\end{array} & \begin{array}{c}if\ y>\bar{y}(\lambda_1)\\if\ y\leq\bar{y}(\lambda_1)\end{array}\end{cases}$$</p>
<p>Further, y is a random variable with distribution $F(\cdot|\lambda_2)$,... | g59775 | [
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<p>In package MASS there is data Insurance packet.
And I need to:
Print table, which row will be Group and column will be Age, in the table should be the sum of Claims meaning.</p>
<p>Can someone help me to do this?</p> | g59776 | [
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<p>Each of the points in the plot below is a mean of 1000 samples. The standard deviation of a point on the RED line is "small" in that it is smaller than the difference between the mean of the RED line and the mean of the GREEN line at that x value.</p>
<p>What is a good clear way to state that the variation of the d... | g59777 | [
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<p>I have learned that a p-value that is less than alpha means you reject the null hypothesis. But this seems to only make sense in the case of lower tail tests. What do you do for upper tail tests?</p> | g59778 | [
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<p>I did lasso selection using <code>lars::lars()</code>, then I got this plot. I have no idea how to interpret it:
<img src="http://i.stack.imgur.com/RYUCw.png" alt="enter image description here"></p>
<p>Could anyone provide a brief explanation? Why does it plot <code>standardized coefficients</code> against <code>|b... | g49570 | [
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<p>Let me present to you the way I have being 'doing' control charts up until now.</p>
<p>I have a series of $k$ samples of size $n$. I calculate the the sample means $\bar{x}_i$ and the grand mean $\bar{\bar{x}}$ --- the mean of the sample means (or the mean of all the $k\times n$ data points). I also calculate the s... | g478 | [
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<p>In the paper </p>
<blockquote>
<p>M. Avellaneda and J. H. Lee, <a href="http://www.math.nyu.edu/faculty/avellane/AvellanedaLeeStatArb071108.pdf" rel="nofollow">Statistical arbitrage in the U.S. equities market</a>, July 2008,</p>
</blockquote>
<p>in the Appendix on page 44, I have some questions.</p>
<p>First h... | g59779 | [
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<p>I have been trying to represent a tree structure as a random graph, but so far my research has led to variations of random graph models and I can't see studies which may help me leverage some of the benefits of random graph models in a more specialized family of graphs. </p>
<p>My data is in the form of tree struct... | g15536 | [
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<p>I am trying to do some web statistics (AdWords). I have a cost, a revenue, and a number of clicks. How do I determine if the difference between cost/click and revenue/click is statistically significant.</p>
<p>I do not have access to the variance nor the standard deviation, of neither the cost nor the revenue.</p> | g59780 | [
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<p>Population stability index quantifies the change of a distribution of a variable by comparing data samples in two time periods. It is very commonly used to measure shifts in scores.</p>
<p>It is calculated as follows:<br>
1) The sample from base period is discretized. Usually it is partitioned into deciles<br>
2) T... | g59781 | [
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<p>I don't know what is the appropriate term for my question. The scenario is described as following.</p>
<p>In the analysis there one dependent variable Y and two independent variable X1 and X2.</p>
<p>All three variables are continuous.</p>
<p>I converted X1 into a categorical variable which has three levels A, B,... | g44832 | [
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... |
<p>The question is the following;</p>
<p><img src="http://i.stack.imgur.com/zuJye.jpg" alt="enter image description here"></p>
<p>And I determine the intervals </p>
<p><img src="http://i.stack.imgur.com/Kpkcs.jpg" alt="enter image description here"></p>
<p>If I Will do breusch-godfred test, I guess accourding to th... | g15542 | [
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<p>I've got data plotted for A/Ci curves (plant physiology, A=photosynthesis rate, Ci=internal CO2 concentration--essentially it's a dose-response relationship). Generally, when this type of data is presented, people just add SE error bars (like the provided image) and if they don't overlap call it significant, or they... | g59782 | [
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<p>I have a problem with my analysis made with R-package dlm.
I have an averaged data vector y, where every yi has variance s2i. On the other words, my data is monthly averages and the standard errors for the means.</p>
<p>What I want to do is take the monthly variance into account in the analysis. In my current model... | g59783 | [
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0... |
<p>I am using Rasmussen's GPML code in Matlab R2011a_student. I have training data (2560x29707) w/ labels (6 classes), and test data (640x29707). To prep the data I have 1. converted from sparse to full, 2. binarized the classes (ie. All classes that = 1 are 1, everything else is -1). I planned on running this 6 times ... | g59784 | [
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0.00409788079559803,
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0.010349661111831665,
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0.0... |
<p>I am estimating a multivariate logit model.</p>
<p>I have included a square term on my main independent variable, IDV and IDV:IDV. And of course a set of control variables.
The results indicate an inverted U shaped relationship; IDV is positive, while IDV:IDV is negative.
I have graphed the probabilities using <cod... | g15547 | [
0.012948298826813698,
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0.01579166390001774,
0.05040778964757919,
0.038300663232803345,
... |
<p>How can I calculate R2 or another measure of explained variance for non-negative matrix factorisation. Currently I calculate the total sum of squares (TSS) as the sum of the squared distance of every data point to the mean and residual sum of squares (RSS) as the squared sum of the distance of every residuum to the ... | g59785 | [
0.011505551636219025,
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0.051564957946538925,
0.03340353071689606,
-0.02... |
<p>I am trying to estimate the mean of a more-or-less Gaussian distribution via sampling. I have no prior knowledge about its mean or its variance. Each sample is expensive to obtain. How do I dynamically decide how many samples I need to get a certain level of confidence/accuracy? Alternatively, how do I know when I c... | g59786 | [
0.0006518448935821652,
-0.025525609031319618,
-0.009368857368826866,
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0.0014251021202653646,
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-0.056567586958408356,
0.0024342022370547056,
0.022257408127188... |
<p>While I know that there are a series of functions for generating heat maps in R, the problem is that I'm unable to produce visually appealing maps. For example, the images below are good examples of heat maps I want to avoid. The first clearly lacks detail, while the other one (based on the same points) is too detai... | g59787 | [
-0.02270193211734295,
-0.02868546172976494,
-0.017971035093069077,
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0.0011232232209295034,
0.004890053067356348,
0.015113315545022488,
-0.014233126305043697,
-0.0658770278096199,
-0.0019599092192947865,
0.03382648527622223,
0.028318993747234344,
0.10689699649810791,
0... |
<p>I am analysing EEG data. </p>
<p>I have data from 19 electrodes from 25 participants divided into two groups (11 and 14 subjects). I asked my student to compare these two groups with some statistical test. </p>
<p>Surprisingly, he calculated means for every electrode (giving two groups with 19 numbers in each). </... | g59788 | [
-0.016583722084760666,
0.02435380406677723,
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0.05469471961259842,
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0.04049065336585045,
0.028354143723845482,
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0.00435446435585618,
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-0.020781980827450752,
0.... |
<p>It is usual to use second, third and fourth moments of a distribution to describe certain properties. Do partial moments or moments higher than the fourth describe any useful properties of a distribution?</p> | g59789 | [
0.02274511009454727,
-0.016524916514754295,
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0.008889949880540371,
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0.0179952010512352,
-0.05086288973689079,
-0.03076133504509926,
-0.019204070791602135,
... |
<p>What is your intuition / interpretation of a distribution of eigenvalues of a correlation matrix? I tend to hear that usually 3 largest eigenvalues are the most important, while those close to zero are noise. Also, I've seen a few research papers investigating how naturally occuring eigenvalue distributions differ f... | g59790 | [
0.01339782029390335,
0.032409556210041046,
-0.001295737805776298,
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0.048097651451826096,
0.015572423115372658,
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0.02252684161067009,
-0.033431489020586014,
0.014132228679955006,
-0.05144805088639259,
0.050430286675691605,
0.0546... |
<p>I have a data set that contains two types of points. The first type of points come from an N(0,1) distribution. The second type of points come from an N(m,v) distribution for some real m and some positive, real v. The objective is to classify each point as type 1 or type 2, and to identify m & v. We have no apri... | g44883 | [
0.035503365099430084,
-0.07101494818925858,
-0.03342854231595993,
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0.000405268045142293,
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-0.010339171625673771,
0.020981021225452423,
0.06455899029970169,
0.055940259248018265,
0.0... |
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