question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>I am running a linear mixed model and want to check its assumptions. The model I run is comparing if males and females behave differently over time (timeclass=1,2,3,4):</p>
<pre><code> x <- lme(response ~ timeclass*sex, random = ~ 1|subject, method="ML", data=dat)
</code></pre>
<p>The code to create the plots:... | 30,166 |
<p>Please help!
I have recently been criticized for using pairwise comparisons to explain all three levels of a factor within a negative binomial GLM rather than all levels at once. I was told that it is "long-winded" and "uneccessary". I was under the impression that in GLMs one cannot bulk all levels of a factor toge... | 73,737 |
<p>I have a time series that follow an MA(1) process , I do non-overlapping aggregation with aggregation level $m=2,3,\dots$, and then I calculate autocorrelation of basic and aggregated series, for negative value of moving average parameter, aggregated autocorrelation becomes close to zero, means that the aggregated s... | 73,738 |
<p>Suppose I have two sets $X$ and $Y$ and a joint probability distribution over these sets $p(x,y)$. Let $p(x)$ and $p(y)$ denote the marginal distributions over $X$ and $Y$ respectively. </p>
<p>The mutual information between $X$ and $Y$ is defined to be:
$$I(X; Y) = \sum_{x,y}p(x,y)\cdot\log\left(\frac{p(x,y)}{p(x)... | 36,199 |
<p>Suppose I have a $95 \%$ confidence interval for $\mu$ with population variance $\sigma^{2}$ known. It will be of the form $$[\bar{X}-1.96 \sigma/\sqrt{n}, \bar{X}+1.96 \sigma/\sqrt{n}]$$ </p>
<p>The statistical interpretation of this is that $95\%$ of the confidence intervals will contain the true mean? I know ind... | 36,200 |
<p>Suppose we have two estimators $\alpha_1$ and $\alpha_2$ for some parameter $x$. To determine which estimator is "better" do we look at the MSE (mean squared error)? In other words we look at $$MSE = \beta^2+ \sigma^2$$ where $\beta$ is the bias of the estimator and $\sigma^2$ is the variance of the estimator? Which... | 36,201 |
<p>Curious whether anyone knows a package, or has written an implementation themselves, for conducting instrumental variables regressions using LIML in R. All of the R packages I have seen for IV regressions seem to resort to 2SLS/GMM as opposed to LIML, which may have more desirable finite sample qualities compared to... | 40,440 |
<p>Are there any statistical concepts or theories on how to effectively measure recency to where recent events are given more weight than older ones. I'm creating a logistic regression model and would like to apply an adjustment to various factors based on the events recency.</p>
<p>...or, is it purely up to me to com... | 73,739 |
<p>For my data, I need to run numerous linear regression analyses, separately for each of my two groups of subjects as well as different conditions. Together, I would have to run approximately 40 regression analyses across the 3 conditions for each group. I'm aware that we should correct for multiple comparisons for th... | 36,205 |
<p>I have a surgical database in which there are approximately 100,000 observations and 200 features. Each observation corresponds to a separate patient while the features correspond to either preoperative, perioperative, or postoperative variables (e.g. preoperative labs, length of operation, and days until death). As... | 43,183 |
<p>We have an events based tracking system for our website, with split testing built-in and we are using <a href="http://www.thumbtack.com/labs/abba/" rel="nofollow">ABBA</a> for the calculations.</p>
<p>The problem comes up when we are doing consecutive split tests. For example, we test X and Y, Y wins, so the next t... | 36,206 |
<p>I sometimes have difficulty understanding the intuition behind some tests. Is it important to know why some test works in a particular situation, or is it enough to learn things at the level "OK, now I can check homoscedasticity" or "I have no idea why we divide by 12 in Mann–Whitney U-test, but trust me, it works"?... | 73,740 |
<p>Principal component analysis <em>can use</em> matrix decomposition, but that is just a tool to get there.</p>
<p>How would you find the principal components without the use of matrix algebra?</p>
<p>What is your objective function (goal), and what are your constraints?</p>
<p>Thanks!</p> | 73,741 |
<p>What is the easiest way / method to compute the correlation between two time series that are exactly the same size? I thought of multiplying $(x[t]-\mu_x)$ and $(y[t] - \mu_y)$, and adding up the multiplication. So if this single number was positive, can we say these two series are correlated? I can think of some ex... | 42,713 |
<p>Can someone tell me why this is wrong: </p>
<p>I want to estimate the goodness-of-fit for a linear mixed effects model. I regress the fitted values against the raw values and calculate an $R^2$. </p>
<p>I suppose an accepted alternative would be to run the model with just the random effect and no fixed effects a... | 36,209 |
<p>I have just been reading a paper which uses the following method to calculate parameter uncertainties from a likelihood surface of two parameters.</p>
<p>Step 1) Calculate the likelihood for finding a given pair of parameters given the data at each point on the grid.</p>
<p>Step 2) Normalise the surface to 1. The ... | 73,742 |
<p>This is an artificial example. I want to compare the Income of the <em>same</em> group of people (i.e. "pairing") while they were working in US, Spain, and Nigeria. In other words, I use the "US" income as a reference and simply conduct 2 Two-sample Paired T-tests:</p>
<pre><code>t.test(dat[Country=="US",]$Income, ... | 73,743 |
<p>I'm trying to generate many draws (i.e., realizations) of
a Gaussian process $e_i(t)$, $1\leq t \leq T$ with mean 0 and covariance
function $\gamma(s,t)=\exp(-|t-s|)$. </p>
<p>Is there an efficient way to do this that wouldn't involve computing the square
root of a $T \times T$ covariance matrix? Alternatively ... | 73,744 |
<p>We have the following points:</p>
<p>$$ (0,0)(1,51.8)(1.9,101.3)(2.8,148.4)(3.7,201.5)(4.7,251.1)(5.6,302.3)(6.6,350.9)(7.5,397.1)(8.5,452.5)(9.3,496.3)$$</p>
<p>How can we find the best fitting line $y=ax$ through the points? My calculator has the option to find the best fitting line $y=ax+b$ through these points... | 36,214 |
<p>I am currently running some analyses on a linguistic data set with a mixed effect model. The problem is, I think that one random factor should be excluded while my colleague thinks it should be included. The two options are:</p>
<pre><code>lmer(intdiff ~ stress * vowel_group + (1|speaker) + (1|word), data)
lmer(int... | 73,745 |
<p>I have samples from two groups. Samples from each group follow a Dirichlet distribution. The two Dirichlet distributions have the same mean but different precision. How to find the MLE of mean and two precisions?</p> | 30,246 |
<p>Suppose you have 2 distinct features x1 and x2 with discrete values between 1 and 10.</p>
<p>When building a neural network, I have 2 options:</p>
<ol>
<li>Create a new feature x3 = 10*x1 + x2 and use this as the only input.</li>
<li>Use both inputs x1 and x2 for the neural network.</li>
</ol>
<p>How can I decide... | 73,746 |
<p>I'm reading through this paper on <a href="http://uai.sis.pitt.edu/papers/11/p736-wilson.pdf" rel="nofollow">Generalised Wishart Processes</a> (GWP). The paper calculates the covariances between different random variables (following <a href="http://en.wikipedia.org/wiki/Gaussian_process" rel="nofollow">Gaussian Proc... | 47,211 |
<p>I'm trying to analyse a dataset to detect fraudulent insurance claims. Unfortunately, other than basic demographics the rest of the claim is a free format OCR scanned text file made from documents submitted by the patient. These documents include lab tests, hospital bills etc., patient summaries. </p>
<p>Right now,... | 73,747 |
<p>I have two matrices with multiple variables. The two matrices come from same sample.I would call them matrix A and Matrix B.Each of them have many correlated variables .</p>
<p>I would want to evaluate the relationship between matrix A and matrix B taking matrix B as explanatory and matrix A as dependent .
When i l... | 36,219 |
<p>I'm working on a random forest classifier with 10-folds CV to aestimate the hyperparameter 'mtry' (chosen by maximizing AUROC). I decided to pre-split the training set in 8 samples equals in size (about 100 observations each).</p>
<p>I iterated the train process 8 times. At each iteration I added one sample to my a... | 73,748 |
<p>I have two datasets, $D1$ and $D2$, each containing many samples $S_i$ of 100 numbers, each sample from a different (unknown) population. For example:</p>
<p>$S_1=\{0.125, 0.122, 0.053, \dots\} \\
S_2=\{0.001, 0.013, 0.034, \dots\} \\
\dots $</p>
<p>The are both quite large. $D1$ contains almost 6M samples, and $... | 73,749 |
<p>I have some data that is bounded between 0 and 1. I have used the <code>betareg</code> package in R to fit a regression model with the bounded data as the dependent variable. My question is: how do I interpret the coefficients from the regression?</p> | 36,223 |
<p>I'm using the <code>igraph</code> package in <code>R</code> to analyze network data. I'm currently trying to calculate some centrality measures for the vertices of my graph and the corresponding centralization scores. My network is both directed and weighted.</p>
<pre><code>require(igraph)
set.seed(12152)
m <... | 32,214 |
<p>Consider a model with a continuous response variable and a categorical explanatory variable. I appreciate that in R, a summary.lm output of an anova on this data gives you rows that represent the mean value of each factor level. The significance stars represent the significance of the difference between the mean o... | 36,225 |
<p>I recently learned about Fisher's method to combine p-values. This is based on the fact that p-value under the null follows a uniform distribution, and that $$-2\sum_{i=1}^n{\log X_i} \sim \chi^2(2n), \text{ given } X \sim \text{Unif}(0,1)$$
which I think is genius. But my question is why going this convoluted way? ... | 73,750 |
<p>What is the best method to determine the minimum number of training samples required for a classifier?</p>
<p>I am only comparing one classifier (four class problem), discriminant function analysis (DFA) with different training sample sizes from different data sets. However, I could be considered to be comparing mo... | 73,751 |
<p>I would like to know what is the theoretical distribution of the vector of (signed) deviances $d_i$ from a logistic regression. Failing that, is there a way to to transform them unto approximately normally distributed r.v.? </p>
<p>My model for the data generating process is the simplest one, e.g.</p>
<p>$$y_i\si... | 73,752 |
<p>I have a set of data points $\{x_i\}$. These data points are grouped so that (say) $i\in\{1,2,3\}$ is group $A$, $i\in\{4,5,6,7\}$ is group $B$, etc.</p>
<p>I would like to test the null hypothesis of no linear relationship between group means and group variances.</p>
<p>A naive approach would be to calculate, for... | 73,753 |
<p>I have a lot of financial instruments and I need to rank them based on price movement "stability", i.e. instruments with with big outliers should have the lowest ranks and instruments with stable and consistent moves should have the highest ranks. To solve this issue I use the ratio of the <code>Arithmetic Mean</cod... | 36,229 |
<p>A co-worker has asked me to help setup a spreadsheet that is used in the analysis of customer care emails. In particular, we are looking at three categories - the assignment of meta-data, content and communication skills.</p>
<p>A typical example question may be:</p>
<p>"How well is the email tailored towards the ... | 73,754 |
<p>Suppose I am building a binary logistic regression model with around 400 variables then how weight of evidence(WOE) can be used in here?
Also, I have known that WOE is helpful in dimension reduction in a model then why not go for factor analysis rather going for WOE?
What should be the size of the number of variable... | 73,755 |
<p>Question: Assume the following classical linear normal regression model:
\begin{gather*}
y_{i} = \beta_1 x_{1i} + \beta_2 x_{2i} + \cdots + \beta_K x_{Ki} + e_i \\
\underbrace{\boldsymbol{y}}_{n \times 1} = \underbrace{\boldsymbol{X}}_{n \times K}\underbrace{\boldsymbol{\beta}}_{K \times 1} + \underbrace{\boldsymbol... | 73,756 |
<p>I'm running the a ridge regression broadly analogous to the one at <a href="http://www.mathworks.com.au/help/stats/ridge.html" rel="nofollow">http://www.mathworks.com.au/help/stats/ridge.html</a>. </p>
<p>However, I have a lot more predictors (12) than the example (which only has 3). Thus when I include the interac... | 36,233 |
<p>Consider an i.i.d. sample $(X_{1},\ldots, X_{n})$ where the $X_{i}$ have density
$f(x) = k \cdot \exp(−(x − θ)^4)$ with $x$ and $\theta$ real, obtain the sufficient statistic and its dimension. What does this example show? Is the statistic that you have found also complete?</p> | 36,235 |
<p>I am looking for a toy similarity matrix of any kind of entity class to test my random walk code. Is there any set like this or how can I create my own set? I need to interpret the results of the random walk that I run to find the dominant instances of the data.</p> | 36,237 |
<p><strong>1. The problem</strong></p>
<p>I have some measurements of a variable $y_t$, where $t=1,2,..,n$, for which I have a distribution $f_{y_t}(y_t)$ obtained via MCMC, which for simplicity I'll assume is a gaussian of mean $\mu_t$ and variance $\sigma_t^2$. </p>
<p>I have a physical model for those observations... | 73,757 |
<p>(1) I preprocessed data with a matching method (CEM)</p>
<p>(2) On this data (binary dependent variable, explanatory variables) , I ran a logit model and estimate predicted probabilities or odds ratios.</p>
<p>I would like to integrate my estimates of the logit model into the potential outcome framework (I would l... | 73,758 |
<p>Is it possible to calculate the correlation between two proportions, while accounting for the individual sample size that is used to calculate the proportion per individual?</p>
<p>For example:
How do I calculate the correlation between the proportion of heads from one coin, and the proportion of heads from another... | 34,909 |
<p>I have two factors: <strong>Brainregion (4 levels)</strong> and <strong>Group (5 levels)</strong>.
Glutamate is my dependent variable.</p>
<p>I am running General Linear Models in SPSS (two factor ANOVA).</p>
<p>Can I get the output in such a way that:
I can compare means (post-hoc test) of control with other lev... | 73,759 |
<p>I am looking for papers, preferably in economics, where simple OLS is used. The reason is that to convey the workings of linear regression, I want to have real data from real papers. Most research uses simultaneous models or other bells and whistles. Also few researchers release their data. I could generate my own d... | 73,760 |
<p>Let $X_1$, $X_2$, ..., $X_n$ be iid RV's with range $[0,1]$ but
unknown distribution. (I'm OK with assuming that the distribution
is continuous, etc., if necessary.)</p>
<p>Define $S_n = X_1 + \cdots + X_n$.</p>
<p>I am given $S_k$, and ask: What can I infer, in a Bayesian manner, about
$S_n$?</p>
<p>That is, I ... | 47,785 |
<p>I am performing multiple t-tests to compare conditions of data. I have had to resort to permutation based t-tests (based on difference of means) due to high variance between samples.</p>
<p>My question is if I am using permutation based t-tests is FWE correction still required? </p>
<p>My understanding is that bec... | 73,761 |
<p>Gelman & Hill (2006) explain how a multilevel regression model can compensate for data sparsity by pooling parameter estimates. But what happens if the data are not sparse at random?</p>
<p>For example, suppose we are evaluating a new blood pressure medication. On every visit we measure a patient's blood pressu... | 73,762 |
<p>I know the value for the 16% quartile, so I know the additive deviation for the given distribution. How do I find the deviation of the log of the given distribution on a multiplicative scale?</p> | 73,763 |
<p>I am trying to figure out good model to analyze social dynamics using a model. I have commenting data from a website. Such as 500 articles, 10000 users, and their 75000 comments. Every user does not comment on every article. </p>
<p>The opinions posed by each user is linked to the opinion of the previous users, as ... | 47,786 |
<p>I previously asked this question: <a href="http://stats.stackexchange.com/questions/24194/winning-percentage-logistic-regression-or-linear-regression">link</a></p>
<p>I've generated the two logistic regression models described in the link using all available data (8 seasons for all 30 teams), and now I want to deci... | 73,764 |
<p>I'm the author of the <a href="http://cran.r-project.org/package=ez" rel="nofollow">ez package</a> for R, and I'm working on an update to include automatic computation of likelihood ratios (LRs) in the output of ANOVAs. The idea is to provide a LR for each effect that is analogous to the test of that effect that the... | 73,765 |
<p>The Gauss-Markov theorem tells us that the OLS estimator is the best linear unbiased estimator for the linear regression model. </p>
<p>But suppose I don't care about linearity and unbiasedness. Then is there some other (possible nonlinear/biased) estimator for the linear regression model which is the most efficien... | 73,766 |
<p>I want to conduct a statistical test that will allow me to say that two populations are similar rather than different. As statisticians know, I can't do this with tests like the T test because the null hypothesis of the test is that the populations' means are equal. Hence my question.</p> | 73,767 |
<p>E.g. from the <a href="http://en.wikipedia.org/wiki/Netflix_Prize" rel="nofollow">Netflix prize</a> I know that the best RMSE = 0.8563 where the test dataset has a size of n=1,408,789.</p>
<p>Can I calculate a boundary for the MAE. If not, why can't I calculate a boundary?</p>
<p>I started like that:</p>
<p>RMSE... | 73,768 |
<p>To apply Bayes inference for data analysis or machine learning, we have to construct <em>prior</em> and <em>likelihood</em>, right? But if I fail to come up with a reasonable <em>prior</em> and <em>likelihood</em>, then the Bayes model will not be meaningful, right?</p>
<p>I wonder is there any technique could be u... | 73,769 |
<p>This should be a fairly straight forward, but I can't seem to figure out the answer. I'm doing some A/B(C/D/E...) testing on a website and measuring impressions and clicks. What method should I be using to determine the statistically significant winner?</p>
<p>This is sample data that I would have. There could be a... | 39,353 |
<p>I am working on Markov transition matrices. I would like to find a statistical test to compare them.</p>
<p>The first matrix is considered the population transition matrix and the second one is obtained by estimation from data (counting the transitions).</p>
<p>My first idea was to use a Chi square test on each li... | 73,770 |
<p>EDIT 2: I originally thought I needed to run a two-factor ANOVA with repeated measures on one factor, but I now think a linear mixed-effect model will work better for my data. I think I nearly know what needs to happen, but am still confused by few points.</p>
<p>The experiments I need to analyze look like this: </... | 47,796 |
<p>I am looking to generate 450 data points in R. There are three distinct sets 150 of each distributed in a circular band with different radii (at 1, 2.8 and 5).</p>
<p>In particular, I'm looking to reproduce the first graph on p546 of The Elements of Statistical Learning.
<img src="http://i.stack.imgur.com/rMILV.png... | 73,771 |
<p>I would like to build a message classification system which classifies a given message into either of 2 class - Relevant/Not.</p>
<p>I don't have any labelled dataset. I only have certain keywords which defines relevance. I can include more keywords (synonyms, nearly same words, etc).</p>
<p>For example: If I want... | 36,243 |
<p>I am working with different transition diagrams and want to calculate the likelihood ratio statistic for testing time-homogeneous. I saw that there are already some comparable questions, but I still don't understand the method. For example, if I have the following transition diagram (probabilities) for 1 year:</p>
... | 73,772 |
<p>Here are my data:</p>
<pre><code> Substrate Species Human.Impact Count
1 rubbles E. quadricolor 0 0
2 corals and rubbles E. quadricolor 0 0
3 corals E. quadricolor 0 4
4 corals and sand E. quadricolor 0 0
5 sand E. quadricolor 0 ... | 36,245 |
<p>I would like to show that $\sum \frac{X^m}{a_n k^2}$ from $k=1$ to $k=n$ converges in distribution to the degenerate random variable 0. We have that some constant $m > 0$, $X$ ~ $Cauchy$, or the ratio of two independent standard Normal random variables, and that $a_n$ goes to $\infty$ as $n$ goes to $\infty$. I a... | 36,247 |
<p>Does anybody have an idea about why conditional correlation between 2 variables is called "partial" correlation and the simple correlation between them (so, when not conditioned on any other variable) is called "marginal" correlation? What is the intuition behind words "partial" and "marginal"? What do they do with ... | 36,248 |
<p>I have a population of interest ($N = 5000$) for which I know some demographic information. I have a sample 1500 members of that population. </p>
<p>So I have a good sized sample, and I know exactly how it is biased (at least based on the demographic information I have). </p>
<p>Is it possible for me to make gener... | 73,773 |
<p>Looking at the <a href="http://www.mrc-bsu.cam.ac.uk/bugs/winbugs/geobugs12manual.pdf" rel="nofollow">GeoBUGS manual version 12</a>, there is a confusion how exactly the <code>car.normal</code> model is specified:</p>
<p>1) at page 12, I read</p>
<blockquote>
<h3>car.normal and car.l1 [top]</h3>
<p>The intr... | 73,774 |
<p>I'd like to match the outputs of lmer (really glmer) with a toy binomial example. I've read the vignettes and believe I understand what's going on.</p>
<p>But apparently I do not. After getting stuck, I fixed the "truth" in terms of the random effects and went after estimation of the fixed effects alone. I'm includ... | 30,414 |
<p>I am using a Neural Networks based classifier to run a classification for my data in n-dimensional.</p>
<p>Then I thought it may be a good idea to run dimension reduction like PCA for my data at first, and then put the PCA results into the classifier (I keep 3 PCs). However, the classification on the dimension redu... | 1,022 |
<p>I'm trying to train a classifier on 10 classes, using 249 samples and a (currently) 16-dimensional feature vector. I'm using an SVM with RBF kernel, through Python's scikit-learn module. The distribution of classes in those 249 samples is as follows:</p>
<p>[6, 45, 51, 38, 34, 23, 12, 15, 19, 6]</p>
<p>When buildi... | 73,775 |
<p>This is nearly the same headline as my previous <a href="http://stats.stackexchange.com/questions/67762/interpretation-of-logistic-regression-intercept-with-one-dummy-coded-categorical">question</a>, but it turned out I was asking about multiple issues. I still have not understood the more basic issues, which have t... | 73,776 |
<p>I am rather new to Matlab and never had a lot to do with statistics, so I apologize already for possibly being ignorant of quite a bit of important knowledge. It also would be nice if you could answer as simple as possible. Thanks ☺</p>
<p>My question is about finding the parameters of a univariate distribution. I ... | 73,777 |
<p>I try to model quasi-poisson family in bugs language, to handle overdispersion. According to <a href="http://www.mbr-pwrc.usgs.gov/software/kerybook/" rel="nofollow">Introduction to WinBUGS for ecologists</a>, this is done by:</p>
<p>$log(\lambda_i) = f(x_i) + \epsilon_i$</p>
<p>$N_i \sim Poiss(\lambda_i)$</p>
<p... | 36,254 |
<p>I've tried to create three models (using R): an intercept only linear regression, a simple mixed effects regression and a by-subject effects mixed effects regression.</p>
<p>An intercept only regression models the grand mean of a response variable plus error. In <code>mtcars</code>, the variable <code>drat</code> m... | 36,255 |
<p>I have a database of time series data generated by giroscope sensor. A small part of the data is already labeled and used to fit the model. My strong assumption is that most of the samples left in this database are of the same class of movement. Can I use this data to replenish the model without manual labeling? Wha... | 36,256 |
<p>Also, are the standardized regression weights equivalent to the correlation between a factor and a manifest variable?</p>
<p>I write this question with reference to an example on p138-142 of the following document: <a href="ftp://ftp.software.ibm.com/software/analytics/spss/documentation/amos/20.0/en/Manuals/IBM_SP... | 36,257 |
<p>Please consider the following panel dataset:</p>
<pre><code>comp obs industry weekDay ind10 ind15 day3 day4 day5 marketRet tweets stockRet
-----------------------------------------------------------------------------------------
1 1 15 3 0 1 1 0 0 0.10 532... | 36,258 |
<p>Given min and max values, how can I estimate shape parameter (tail index) of data generated by truncated pareto distribution ? I see a package tpareto but find no information on how to estimate tail index from given data.</p>
<p>kindly help.</p> | 36,260 |
<p>Suppose I have a dataset $x_i$ (with $x_i >= 0$) of N samples. I would like to determine the average of the data when the data is limited to some theshold c: </p>
<p>$limitedaverage(x,c) = \frac{1}{N} \sum_{i=1}^N max(x_i,c)$</p>
<p>Problem is I don't have access to the actual samples, I only know some aggregat... | 73,778 |
<p>How can a stationary, invertible ARMA(1,1) process be represented as
either an infinite order AR or infinite order MA process?</p> | 73,779 |
<p>I am investigating the achieved mark in a math test in grade 8 in two different cities. The plot shows the two <em>Empirical Cumulative Distribution Functions</em> (<em>ECDF</em>).</p>
<p><img src="http://i.stack.imgur.com/6vLlw.png" alt="Plot of two ECDFs"></p>
<p>How can I evaluate whether these two <em>ECDFs</e... | 73,780 |
<p>I'd be really grateful for recommendations of a robust package for fitting discrete choice models to a large amount ($n$ in the millions and $p$ in 2000 range) of data. I want a smoothed model that can deal with multi-colinear dependent variables and matrix inversion issues sensibly - like <a href="http://cran.r-pro... | 73,781 |
<p>I am trying to use <code>randomForest</code> in R to find interaction terms to add to a model. My plan was to fit trees with <code>maxnodes=4</code> (two deep stubs), then compute how often <code>var A</code> is a child of <code>var B</code> and its improved accuracy to measure the importance of the <code>A*B</code... | 36,265 |
<p>I have a general question about interpreting interaction effects in a non-linear model. I understand the reasons Ai and Norton (2004) suggest using the stata inteff command to help interpret interaction effects in a non-linear model.</p>
<p><a href="http://www.unc.edu/~enorton/NortonWangAi.pdf" rel="nofollow">http:... | 73,782 |
<p>This is bordering on a philosophical question, but I am interested in how others with more experience think about distribution selection. In some cases it seems clear that theory might work best (mice tail lengths are probably normally distributed). In a lot of cases there is probably no theory to describe a set of ... | 73,783 |
<p>I want to compare the distributions of $K$ contingency tables, where each table is $N \times M$.
To make things clearer, let's work on $K=M=N=2$.
Suppose I have a classical cases and controls test, where I have $2$ variables, treated or not, and cured or not.
Suppose that besides testing whether the treatment is eff... | 40,857 |
<p>I am just learning R. I have developed a regression model with six predictor variables. While developing it, I found the relationships are not very linear. So, maybe because of this the predictions of my model are not exact.</p>
<p>Here is Headers of my data set:</p>
<pre><code>1.bouncerate(To be predicted)
2.avgS... | 49,923 |
<p>I'm doing statistical analysis on a psychology study I ran a short while ago, and I'm starting to think that I've designed myself into a corner.</p>
<p>In the study, we measured participants' pointing responses after traveling in a virtual environment. There were three factors, each nested within another:</p>
<p>P... | 73,784 |
<p>Yesterday i read this blog post <a href="http://www.petrkeil.com/?p=393" rel="nofollow">Predictors, responses and residuals: What really needs to be normally distributed?
</a>
and I wonder what do you think about it. Personally I totally agree with the author about the fact that sometimes people even discard to bu... | 47,833 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/35719/improvement-of-regression-model">Improvement of regression model</a> </p>
</blockquote>
<p>I have recently started learning regression. I have a dataset containing a response and a predictor variable... | 49,923 |
<p>Is there a Box-Cox like transformation for independent variables? That is, a transformation that optimizes the $x$ variable so that the <code>y~f(x)</code> will make a more reasonable fit for a linear model?</p>
<p>If so, is there a function to perform this with <code>R</code>?</p> | 49,507 |
<p>I am not entirely sure if I should ask this question here, but does EViews has a function of converting <em>J</em> statistics to <em>p</em>-value of Jstats, or other way around. I am running several GMM estimations and I would like show both of them in my paper. Or is their a way to convert the <em>J</em> statistic... | 12,399 |
<p>I have a sample design that can be resumed in:</p>
<ol>
<li>Split the city in X areas and, for each area, sample 5% of the residences and get some informations about it;</li>
<li>For each residence, interview ALL residents;</li>
<li>In the end, weights to homes and residents are calculated.</li>
</ol>
<p>So, actua... | 73,785 |
<p>I am thinking about how best to construct a data set containing one record for every individual in the entire United States population starting from something like the <a href="http://www.asdfree.com/search/label/american%20community%20survey%20%28acs%29" rel="nofollow">American community survey</a> or the <a href="... | 73,786 |
<p>The regret in a multi-arm bandit model is given by </p>
<p>$$\underset{j}{\max}\sum_{t=1}^{T}x_j(t) -G_{A}$$</p>
<p>where $$G_A=\sum_{t=1}^{T}x_{it}(t)$$ is the total reward achieved by the learner, based on an action $i$, taken at each time interval $t$, i.e $i_{t}\in {1,2,...,K}$ and $x_j(t)$ is the reward assos... | 36,273 |
<p>How many lags should one use a Ljung-Box test for the returns on 1320 daily price quotes? Is there a rule of thumb? What is exactly the impact in the end result of misuse of lag number?</p> | 36,274 |
<p>I have four sets of data grouped by stages (Stage 1-4) with each having their own correlation coefficient. The 4 sets of data has the same dependent and independent variables with 1st n=106, 2nd n=23, 3rd n=89, 4th n=132. My hypothesis is that at stage 4 the correlation would get weaker.</p>
<p>From the numbers alo... | 73,787 |
<p>I would like to try to make some sense of a neural network. The neural network has a single hidden layer and is used on 30-40 attributes, which are used to classify the probability that the observation belongs to 1 of 3 different classes. My goal is to the find 5-10 main interactions in order to understand the model... | 73,788 |
<p>I'm creating Poisson GLMs in R. To check for overdispersion I'm looking at the ratio of residual deviance to degrees of freedom provided by <code>summary(model.name)</code>. </p>
<p>Is there a cutoff value or test for this ratio to be considered "significant?" I know that if it's >1 then the data are overdispersed,... | 73,789 |
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