question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I am currently working on a regression model where I have only categorical/factor variables as independent variables. My dependent variable is a logit transformed ratio.</p>
<p>It is fairly easy just to run a normal regression in R, as R automatically know how to code dummies as soon as they are of the type "factor... | g14664 | [
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<p>Also, how do I find if there is a significant difference in the number of males in two populations? In SPSS please!</p> | g59220 | [
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<p>I have a two kinds of data for the same geographic region. One is presence-absence data of species (for amphibians, reptiles and birds) and the other has several environmental variables for the same area (e.g. temps and precipitation). For the species I calculated the Hellinger distance and for environmental variabl... | g38632 | [
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<p>I'm preparing a presentation on missing data strategies and conducted a simulation to compare listwise deletion (LD) to the EM. Here's what I expected based on the literature:</p>
<ol>
<li>Standard errors will be smaller for EM under all missing data conditions (MAR, MCAR, NMAR). See <a href="http://psycnet.apa.org... | g59221 | [
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<p><strong>Background</strong></p>
<p>A couple of days ago I asked here about: <a href="http://stats.stackexchange.com/questions/104388/how-to-reduce-number-of-points-for-clustering">How to reduce number of points for clustering</a> . Instead of reducing number of points, a method "Kernel Density Estimation" (KDE) was... | g14666 | [
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<p>I'm doing a Cox regression analysis in order to verify the role of two variables on the prediction of disease conversion. Previously, I did a ROC analysis and a logistic regression. All these methods reported an important role of one of the two variables (<code>Var1</code>) to predict the presence of disease. When I... | g14667 | [
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<p>I've struck an unpleasant problem with the noncentral $\chi^2$ distribution.</p>
<p>I work with random variables, distributed as $\chi^2_{\nu}(\lambda)$, where $\nu$ is the degree of freedom and $\lambda$ is non-centrality parameter (which should be somehow estimated).</p>
<p>In "Continuous Multivariate Distributi... | g14668 | [
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<p>I apologize for the simplistic questions. I have a retrieval process that has a set of random and systematic uncertainties associated with it. I'm assuming that these are all independent. The goal is to find the total error for this process. I have two questions related to this:</p>
<p>1) To find the total systemat... | g59222 | [
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<p>I calculated the 5 year survival of two populations keeping different variable constant each time and got percentages.
I wanted to determine if these percentages were significantly different from each other.
Could anyone please guide me with the same?</p> | g59223 | [
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<p>Here I perform a GLS regression in R and the degrees of freedom is reported as "Degrees of freedom: 60 total; 58 residual". In this regression I see five parameters that are being estimated: the slope of the regression line, the intercept of the regression line, the residual standard deviation, the constant of the v... | g14670 | [
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<p>I have been unable to understand the highlighted subsection of David Kenny's <em>Correlation and Causality</em>, which I downloaded from <a href="http://davidakenny.net/doc/cc_v1.pdf" rel="nofollow">Kenny's website</a>.</p>
<p><img src="http://i.stack.imgur.com/j57ti.png" alt="enter image description here"></p> | g59224 | [
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<p>I'm writing a paper on a method to determine the statistical significance of whether a sample of sources are in mutual agreement on specific premises. This is done by counting the number of sources in the sample that agree with the premise, and the number of sources that disagree, and subjecting them to a formula to... | g14672 | [
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<p>I ran an experiment where each participant had to choose 1 image from a 4-image display and I measured whether the image they chose was from category A. I want to compare the average proportion of images chosen from category A to the actual proportion of images from category A. </p>
<p>For example: a trial would be... | g59225 | [
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<p>Suppose I have two discrete independant random variables $X$ and $Y$, and that I'm interested in the expected value of the random variable $W$, where:
$$
W= \text{sign}(X-Y).
$$
So, W is 1 if $X>Y$, -1 if $Y>X$ and 0 otherwise. </p>
<p>I sample the distributions of $X$ and $Y$ ten times each, giving me $\{X_... | g59226 | [
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<p>So I am working on a problem where I want to extract a set of LDA topics from one corpus, and then compare the distribution of those topics in other corpora. So basically I want to lock-in the topics and then get a sense of how similar or different another corpus is from the original corpus. I was hoping that someon... | g59227 | [
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<p>On one hand, </p>
<p>I have a temperature time series data (dataset1) for a week and I want to build the temporal correlation model by using time-series analysis and performing the prediction for oncoming values. The data is not sufficient and doesn't include seasonal and diurnal patterns to result accurate predic... | g59228 | [
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<p>I have something like that:
$$ Var\left( \frac{1}{2n-2} \sum_{i=1}^{n-1} \left( X_{i+1}-X_{i}\right)^{2} \right) $$
and I transformed it to something like that (I hope it is correct):
$$ \left(\frac{1}{2n-2}\right)^{2} \sum_{i=1}^{n-1} Var(X_{i+1}^{2}-2X_{i+1}X_{i}+X_{i}^{2}) $$
What can I do more with that, whe... | g59229 | [
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<p>I understand the concept of scaling the data matrix to use in a linear regression model. For example, in R you could use: </p>
<pre><code>scaled.data <- scale(data, scale=TRUE)
</code></pre>
<p>My only question is, for new observations for which I want to predict the output values, how are they correctly scaled... | g3232 | [
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<p>I've a small query and really confused as how to solve such problems.</p>
<p>$n$ people are question about internet connection 87 of them have high speed connection. We are given confidence interval(CI) of population proportion is $0.119 < p < 0.1771$.</p>
<ol>
<li>I found the mid-point of CI as 0.145. I nee... | g14677 | [
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<p>Often introductory applied statistics texts distinguish the mean from the median (often in the the context of descriptive statistics and motivating the summarization of central tendency using the mean, median and mode) by explaining that the mean is sensitive to outliers in sample data and/or to skewed population di... | g14678 | [
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<p>There are a lot of statistical methods that rely on the assumption of input independence. For example, Naive Bayes text classifiers operate under the assumption that occurrences of different words are conditionally independent given the document class. Another example - HDMR and Sobol variance decomposition seem lik... | g59230 | [
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<p>Is there a package in R which implements the weighted maximum likelihood method (Warm, 1996) for estimating the person parameters in Rasch Models?</p> | g14680 | [
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<p>I am working on a spatial linear regression and I can tell there is collinearity between covariates. Can I use PCA (Principal Component Analysis) images instead of original covariates to estimate the dependent variable? I am assuming PC1=Variable 1, PC2=Variable 2, etc. Or are there any other methods to solve the co... | g59231 | [
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<p><a href="http://stats.stackexchange.com/questions/66533/seemingly-unrelated-regression-and-multivariate-regression">It's been said that</a> SUR is equivalent to the equation-by-equation OLS:</p>
<blockquote>
<p>i. When there are no cross-equation correlations between the error terms.<br>
ii. When each equation ... | g14958 | [
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<p>I've read some literature that random forests can't overfit. While this sounds great, it seems too good to be true. Is it possible for rf's to overfit?</p> | g59232 | [
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<p>what is the difference between imputation and forecasting? All i know, forecasting is the term used in time series analysis, which means predicting the future value by considering the trend of the historical data. Imputation is a strategy for completing data. I've thought some answers to my own question. But so far,... | g59233 | [
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<h2><strong>Background</strong></h2>
<p>I want to find a probability measure for a continuous random variable, subject to moment constraints, that is maximally "uniform", as defined below: </p>
<hr>
<p><strong>Definition: Maximally Uniform Probability Measure</strong></p>
<p>Let $X$ be a continuous random variable ... | g59234 | [
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<p>The caret package (terrific btw) has a lot of models built in but if you want to use a model that is not built in, there is a way as described in outline here <a href="http://caret.r-forge.r-project.org/custom_models.html" rel="nofollow">http://caret.r-forge.r-project.org/custom_models.html</a>. Reproducing the exam... | g59235 | [
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<p>Suppose the target population is a group of 11 company CEOs and 7 CEOs responded to a question about their level of annual bonus on a 7 point Likert scale. </p>
<p>The responses are as follows: 7, 7, 7, 7, 7, 7, and 5. The average response score then is 6.71.</p>
<p>If the last two levels of the Likert scale are '... | g43819 | [
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<p>I have asked following questions before</p>
<p><a href="http://stats.stackexchange.com/questions/20988/more-than-one-outcome-dependent-variables-in-ordinal-logistic-regression">More than one outcome (dependent) variables in ordinal logistic regression</a></p>
<p><a href="http://stats.stackexchange.com/questions/20... | g14682 | [
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<p>Which survival packages in R explicitly allow for time dependent covariates?</p>
<p>By explicitly, I mean that the package allows its models to accept a survival object with the form </p>
<pre><code>Surv(start,stop,event)~....
</code></pre>
<p>For example, the cox proportional hazards model with time dependent co... | g59236 | [
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0.02310... |
<p>I'm trying to predict the gender of French nouns based on their suffixes. I have a corpus of 10k nouns. For each noun, I split the root from the suffix. I create five instances but with varying suffix lengths: 1, 2, 3, 4 and 5.</p>
<p>The class name I'm assigning to each instance is composed of the gender and the l... | g59237 | [
-0.022410083562135696,
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... |
<p>The Minimum Covariance Determinant (MCD) estimator may be used to achieve robustness when estimating a covariance matrix. It looks for the subset of $h$ data points (out of $n > h$) whose covariance matrix has the smallest determinant and it computes the covariance of those $h$ points.</p>
<p>Why does minimising th... | g59238 | [
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0.03394901379942894,
0.01942070946097374,
0.046... |
<p>Is there any way to conduct a partial correlation analysis if the DV is dichotomous?</p> | g59239 | [
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0.... |
<p>I'm a programmer/database developer, not a statistician, so I'm just looking to be pointed in the right direction here. I've got enrollment data for conference sessions going back 5 years. I have weekly enrollment figures for each session 9 months before the start of each session and then I have the final tally afte... | g59240 | [
0.016451461240649223,
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0.02099565416574478,
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0.04473299905657768,
0.0... |
<p>If I were expressing a problem in terms of binary features, all encoded as {0,1}, could I boost some features by encoding them as {0,2}? Would the effect change based on whether I used either of the approaches above (logistic regression or linear SVMs?) Any paper recommendations that would explain the mathematics?... | g59241 | [
0.015170526690781116,
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-0.003302793251350522,
0.0024789918679744005,
0.07999763637781143,
0.0553821325302124,
0.0... |
<p>I have 35 binary events (presence/absence coded as 1/0) that describe 7 questioned samples (QS 1...7) and 1 known sample (KS). I am asked to provide a probability (in percentage) of how likely it is that one of the questioned samples (QS 1...7) <strong>matches</strong> the known sample (KS). Due to time and budget f... | g59242 | [
0.009863807819783688,
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0.009190147742629051,
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0.0008134834351949394,
0.01956005021929741,
0.0... |
<p>I'm considering building MATLAB and R interfaces to <a href="http://en.wikipedia.org/wiki/Ross_Quinlan">Ross Quinlan</a>'s <a href="http://rulequest.com/download.html">C5.0</a> (for those not familiar with it, C5.0 is a decision tree algorithm and software package; an extension of <a href="http://en.wikipedia.org/wi... | g43858 | [
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0.... |
<p>Does anyone know which is the best bayesian network program for mac that has a graphical interface and is free?</p> | g14691 | [
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0.022407291457057,
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0.039323195815086365,
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0.01688777096569538,
0.02... |
<p>I have the following weights from a consumer price index. </p>
<pre><code>P-Weight Percentage
2.5746 19.54%
2.3506 17.84%
1.7585 13.35%
1.1223 8.52%
0.9277 7.04%
0.8048 6.11%
0.8709 6.61%
0.4867 3.69%
0.482 3.66%
0.3714 2.82%
0.5208 3.95%
0.3679 2.79%
0.3782 2.87%
0.1594 1.21%
</code></pre>
<p><a ... | g14692 | [
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0.0070459069684147835,
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-0.010795763693749905,
-0.007474046666175127,
0.013383499346673489,
0.06872330605983734,
-0... |
<p>I am attempting to run an OLS regression:</p>
<ul>
<li><p><strong>DV: Change in weight over a year (initial weight - end weight)</strong></p></li>
<li><p><strong>IV: Whether or not you exercise.</strong></p></li>
</ul>
<p>However, it seems reasonable that heavier people will lose more weight per unit of exercise t... | g59243 | [
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0.013182185590267181,
0.04454147815704346,
0.019527647644281387,
-0.0... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/7004/calculating-required-sample-size-precision-of-variance-estimate">Calculating required sample size, precision of variance estimate?</a> </p>
</blockquote>
<p>I would like to present some measure of how... | g49550 | [
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0.026426125317811966,
0.0054231504909694195,
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-0.026602908968925476,
-0.0024670215789228678,
0.05919912829995155,
0.017751581966876984,
... |
<p>I was reading the short intro to nonlinear regression in R by John Fox (<a href="http://cran.r-project.org/doc/contrib/Fox-Companion/appendix-nonlinear-regression.pdf" rel="nofollow">Link</a>)</p>
<p>and was wondering where the formula for the variance of the coefficients come from (page 1). The formula for the var... | g59244 | [
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0.005474971607327461,
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0.038389820605516434,
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-0.03142498806118965,
0.03830491378903389,
0.028258247300982475,
-0.008... |
<p>I'm trying to understand the following claim:</p>
<blockquote>
<p>if the $t$-statistic is greater than
zero, it indicates that the variable
is explosive... but does that mean it
has unit root?</p>
</blockquote>
<p>In the context of <strong>Dickey Fuller</strong> test.</p> | g59245 | [
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0.043549660593271255,
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0.0006049766670912504,
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0.05105218663811684,
0.04197585955262184,
-0.028... |
<p>How would you go about explainin "Stambaugh Bias" in simple relatively non-technical language?</p> | g14694 | [
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0.030233491212129593,
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0.009738754481077194,
0.011036388576030731,
0.0... |
<p>I'm looking at p. 355 of Gelman's <em>Bayesian Data Analysis</em> (3rd ed.), for which there is no errata, and I see this:</p>
<blockquote>
<p>In the normal regression model, a convenient non-informative prior
distribution is uniform on $(\beta,\, \log\sigma)$ or, equivalently,
$$p(\beta,\, \sigma^2|X) \propt... | g59246 | [
0.037889041006565094,
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0.032932769507169724,
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0.06953608989715576,
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-0.013652046211063862,
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0.05116557329893112,
0.02970510721206665,
-... |
<p>Is there a way to test for the significance of the difference-in-differences in adj. R²s in Stata?</p>
<p>Let's say I have four subgroups: pre-treatment, pre-control, post-treatment, post-control and I want to figure out whether the difference-in-differences of the adj. R² of the same regression (e.g., R² of Y = b0... | g14696 | [
-0.04732732102274895,
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0.03941759094595909,
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0.07673075050115585,
0.0003975273866672069,
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-0.026649363338947296,
0.0017386317485943437,
0.05937248840928078,
0.028909049928188324,
... |
<p>I was wondering if anyone had ever used down-sampling to build random forests with data that has unbalanced classes. Basically down-sampling samples (with replacement) x*min from the population where x is the number of classes and min is the size of the smallest class. So it is sampling min number of observations fr... | g59247 | [
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0.059806931763887405,
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0.012369167990982533,
0... |
<p>I'm interested in assessing model performance on data with an ordinal categorical dependent variable. For my use case, the ideal metric would: </p>
<p>1) Not assume equal intervals between classes or that recoding to a continuous scale is appropriate<br>
2) Be scale independent<br>
3) Give preference to models tha... | g43867 | [
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0.006543062627315521,
0.04047910496592522,
0.018860993906855583,
0.06338228285312653,
-... |
<p>I have a cognitive architecture solving a set of tasks. Also I have data of human subjects solving the same set of tasks.</p>
<p>Now I want to see whether I can find a relationship between the performance of the architecture and that of human subjects (e.g: if its hard for the architecture its also hard for human s... | g59248 | [
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0.02372119389474392,
0.010205728001892567,
-0.03137959912419319,
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0.... |
<p>Is this the correct formula for combining the standard deviations of 3 groups?</p>
<p>$$
\sigma = \sqrt{\frac{n_1\sigma_1^2 + n_2 \sigma_2^2+ n_3 \sigma_3^2+ n_1(\mu_1-\mu)^2 +n_2(\mu_2-\mu)^2+n_3(\mu_3-\mu)^2}{n_1 + n_2 +n_3 }}
$$</p> | g293 | [
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0.02617942914366722,
0.004111539106816053,
0.011739100329577923,
-0.03589967265725136,
-... |
<p>First of all, I’m new to statistics and this is the first time I am trying to apply it to a real world problem.</p>
<p>I am doing analysis of a series of observations of a variable over all weeks of a year. During certain weeks an event happened that I believe has impacted the variable and I want to check for this.... | g14700 | [
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... |
<p>I have a set of data that are binomial, and am comparing them across 9 years. The first 5 years have low sample sizes ($~n=20$) and the last 4 have $n>100$. I've run a glm in R with the family set to "binomial", and the results look reasonable.</p>
<p>However, when I did the multiple comparisons afterwards using... | g59249 | [
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0.009125761687755585,
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0.019861703738570213,
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0.004809132311493158,
0.0037047965452075005,
0.00024649000260978937,
0.017067866399884224,... |
<p>In many studies of heritability, researchers study identical twins raised apart and raised together, and see how much a trait correlates between the two types of twins. Sometimes they use fraternal twins, there are a few variations on the scheme.</p>
<p>But while we can measure how similar two people are in terms o... | g14702 | [
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0.019137879833579063,
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0.005916554480791092,
0.... |
<p>I have several test results of server response delay. According to our theory analysis, the delay distribution (The probability distribution function of response delay) should have heavy-tail behavior. But how could I prove that the test result does follow heavy-tail distribution?</p> | g14703 | [
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<p>If you use 10-fold cross validation to derive the error in, say, a C4.5 algorithm, then you are essentially building 10 separate trees on 90% of the data to test on 10% - 10 times. Which one of the 10 trees is representative? Won't they all be different?</p>
<p>For example - how does WEKA give me a C4.5 tree and a ... | g38932 | [
0.05619051679968834,
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0.024090053513646126,
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0.014297882094979286,
0.04628608748316765,
0.0283... |
<p>I've ran across a type of classification problem that I don't think fits into the traditional multi-class framework. Just wanted to run it across you guys to see if you had any ideas. So</p>
<p>Lets say we have 3 drugs - drug A, B, C - and we serve it to 100 patients</p>
<p>The for each patient we have three types... | g59250 | [
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0.058329612016677856,
0.03158867731690407,
0.07679620385169983,
... |
<p>I have been asked to do some real time data analysis. The data values represent parameters of phone calls for a telco (like number of calls, call length, etc.) If the numbers suddenly drop or spike, I'm supposed to raise an alarm. Normal noise is expected, but we want to know if things change suddenly, like if no... | g59251 | [
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0.013179426081478596,
0.08286385238170624,
... |
<p>I am attempting to write a program that will (among other things) use the F-test in multivariate regression under standard robust errors. I am having trouble finding a specific formula for the F-statistic using robust errors. </p>
<p>I understand the purpose of robust errors. I simply need the modified formula for... | g59252 | [
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0.018105022609233856,
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0.05949227884411812,
-... |
<p>I'm working on a project that involves collecting crowd-sourced labels for discussion forum posts. The task given to annotators was to look at a forum post and to decide which of six classes the post belonged to. Each post was labelled once by five different annotators, so we have five redundant labels per post. The... | g14706 | [
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0.042796164751052856,
0.018398012965917587,
-0.029279418289661407,
0.0015008685877546668... |
<p>I am studying banks behaviour according to 6 financial rations throughout a 3-years period. I have 32 observations separated into two groups: large (6) and medium-sized banks (26). However, since in my country there are exactly 6 large banks, it does not constitute a sample, but a population, where as there are arou... | g59253 | [
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0.0023997498210519552,
0.04321707785129547,
0.033655084669589996,
-0.030529094859957695,
... |
<p>What are the potential reasons why the relationships are insignificant in my regression model, and what can I do to increase significance?</p> | g59254 | [
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0.004626605659723282,
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0.032368846237659454,
0... |
<p>I'm creating and OCR app, and so far it seams to work. It's quite similar to example from Coursera - Machine learning course. </p>
<p>Output layer of network has as many neurons as classes needed to recognize, 10 digits, 26 letter and alike. When the network is trained, it should basically output [1,0,0...0] for le... | g14709 | [
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<p>I want to better understand the R packages <a href="http://www.stanford.edu/~hastie/Papers/LARS/LeastAngle_2002.pdf"><code>Lars</code></a> and <a href="http://www.stanford.edu/~hastie/Papers/glmnet.pdf"><code>Glmnet</code></a>, which are used to solve the Lasso problem:
$$min_{(\beta_0 \beta) \in R^{p+1}} \left[\fra... | g14710 | [
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<p>Three independent samples $(X_1,X_2,...,X_n)(Y_1,Y_2,...,Y_n)$ and $(Z_1,Z_2,...,Z_n)$ are drawn from normal population, each having the same unknown variance $\sigma^2$ but, $E(X_i)=m_1,E(Y_i)=m_2,E(Z_i)=m_1-m_2,\forall i$,show that the test of $H_0:m_1=\lambda m_2$ can be carried out by the test statistic $$T=\fra... | g59255 | [
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... |
<p>I am getting started in R. I need help with a command to:</p>
<p>"Simulate 10000 binom(20,0.3)-RV's". I would do it like:</p>
<pre><code>binsim <- rbinom(10000, 20, 0.3)
</code></pre>
<p>Question cont.: "Let X be a binomial(20,0.3)-RV. Use simulated numbers to estimate:
P(X<=5) and P(X=5)"</p>
<p>Okay for ... | g14711 | [
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... |
<p>I have seen that multiple correspondence analysis (MCA) can also be seen as a generalization of principal component analysis when the variables to be analyzed are categorical instead of
quantitative. In SPSS I have found both CATPCA (Categorical Principal Components Analysis) and MCA under the optimal scaling proced... | g14712 | [
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<p>I am doing a correlation analysis testing summated likert scales. However, one of the correlation analysis shows an unsignificant pearsons r (p = 0.068), BUT spearman's rho is 0.044. What should I conclude from that?</p>
<p>I know that likert scales are ordinal, but to run the correlation analysis I am assuming int... | g59256 | [
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<p>I have a scenario where both factors are within-subject. One is time (5 levels) and one is condition (2 levels). The time point of 0 was only measured once in each subject, and is a 'resting value' that is to be used as the time point of 0 for both conditions. I cannot find a way of dealing with this accept for ente... | g43884 | [
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<p>I am interested in the distribution of/performing inference on the 'achieved' $R^2$ coefficient in multiple linear regression. Suppose that $y\sim x\beta + \epsilon$ with $\epsilon \sim \mathcal{N}\left(0,\sigma^2\right)$, where $x$ is a $p$-vector. You observe $x_1,x_2,\ldots,x_n$ and corresponding $y_1,y_2,\ldots,... | g43885 | [
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0.02... |
<p>Some <a href="http://stats.stackexchange.com/questions/18030/how-to-select-kernel-for-svm/18032#18032">answers to other questions</a> on kernel selection suggest using invariances known about the problem domain, and choosing a kernel that preserves such invariances.</p>
<p>Can you give an explicit example of it's d... | g14713 | [
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0.03704901784658432,
0.06700... |
<p>I would like to know if it makes sense to run an ordered probit regression (dependent variable is ordinal with three outcomes) with only categorical explanatory variables (some are dichotomous e.g. gender; others are categories that have been entered as dummy variables e.g age). Thanks</p> | g401 | [
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<p>I am trying to prioritize customer tickets (issues/change requests). I have identified a few parameters to prioritize the tickets in the queue. </p>
<p>The parameters are:</p>
<ol>
<li>Criticality of the issue (minor - 100 points, major - 200 points and critical - 500 points). </li>
<li><p>Type of customer - Silve... | g14716 | [
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0.02... |
<p>My question is when to average samples or when it is allowed to apply a mixed effects model.</p>
<p>I have the following constellation:
there is a cell-line experiment conducted in a 96-wellplate, meaning that we have cell material from the same source but incubate samples in 96 individual wells on one large plate ... | g59257 | [
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... |
<p>I'm investigating environmental effects (wind) on acoustic receiver detection probability for two types of transmitters using a binomial glmer. While my model analysis indicates that there's a significant effect between wind speed and transmitter type, graphical visualisation does not confirm this. If I'm correct, a... | g59258 | [
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<p>While I was reading Torgo's Data Mining with R, I found that the description of precision/recall curve was different compared with other approaches. Usually, these curves are based on a threshold that determines which probability value is good enough to decide when an event has occurred, so we can classify future ev... | g1077 | [
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<p>I intend to assess Granger Causality between three endogenous variables, where one of these variables is a dummy variable, indicating specific events during the continuous time frame. </p>
<p>I was wondering whether normal Granger Causality tests can be used in the this case. I presume that I can, since the GC test... | g59259 | [
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0... |
<p>I observe a process in which particles could be detected on a start point, and sometimes cross a border. So I count the number of particles during the days. Which non-parametric method would you suggest to clarify if the difference or ratio of start and cross border factors is different between two given days?</p>
... | g14722 | [
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... |
<p>I have a question regarding to the concept of robust standard errors. What I found about that topic is, that one can estimate the robust standard error for regression coefficients to eliminate problems with heteroscedasticity (when one wants to interpret a model). I want to know if there is a way not only to determi... | g59260 | [
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0.03942738100886345,
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0.036269526928663254,
0.02069210447371006,
0.013639... |
<p>The adjusted $R^2$ is not shown when a regression with robust standard errors is calculated in Stata.
This is surprising to me since the value of the $R^2$ is unaffected in regressions with robust standard errors.</p>
<p>Is there any statistical reason for not quoting the adjusted $R^2$ when using robust standard e... | g14725 | [
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0.042... |
<p>I wish to find comparable SDs/Confidence Intervals for two parameters.
One parameter has been measured by only one (new) study that reports the standard error. Here, <em>t</em> value, sample size and SD are provided.
The other (a correlation coefficient) has been measured by 10 (older) studies, in some as a mean ac... | g14726 | [
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0.03138723224401474,
0.020003022626042366,
0.04386380687355995,
... |
<p>I am running a Bayesian regression model by WinGUBS via R2WinBUGS package in R. Everything looks fine except for one parameter:</p>
<pre><code>nlssim$summary[37,][c(1,2,8,9)]
mean sd Rhat n.eff
3.054326e-05 9.523965e-06 1.000000e+00 1.000000e+00
</code></pre>
<p>The number of effecti... | g59261 | [
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0.012959109619259834,
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0.06453946232795715,
-0.003300776705145836,
... |
<p>I seem not to find this in any textbooks. So I post these questions.</p>
<ol>
<li>Is monthly data better than weekly data for forecasting?</li>
<li>Can there be seasonality in weekly data? Most software/methods don't seem to find seasonality in forecasting data.</li>
<li>Is there a way to aggregate weekly data to ... | g59262 | [
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0.08496657758951187,
0.00161848240531981,
0.10915784537792206,
0.0039... |
<p>I was recently looking at a paper in the journal <em>Psychological Science</em> and came across this:</p>
<p><em>F</em>(1, 71) = 4.5, <em>p</em> = .037, $\mu^2$ = .06</p>
<p><em>F</em>(1, 71) = 0.08, <em>p</em> = .78, $\mu^2$ = .001</p>
<p>I was wondering what the $\mu^2$ is in the above. Typically in APA the thi... | g59263 | [
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... |
<p>I am using Stata for a survival analysis project involving inverse probability weighting (IPW). The question has arisen as to how to analyze weighted continuous data between two groups with a Wilcoxon rank sum test? Is this easily implemented in any other package? </p> | g14728 | [
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0.0010294695384800434,
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<p>I have two questions regarding the AIC criterion : AIC=$2k-2ln(l)$</p>
<p>Where does the number 2 comes from? As we usually minimize it why don't we consider only : $k-ln(l)$. (Maybe I am missing something.)</p>
<p>Second question : Can we consider that AIC selection follow the same "philosophy" as lasso/ridge sel... | g59264 | [
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0.034880902618169785,
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0.11460501700639725,
0.031... |
<p>Suppose four numbers $\{a,b,c,d\}$ where $a$ and $c$ random variables from a continuous distribution with support on $\mathbb{R}$.</p>
<p>Does $b\neq d$ imply $|a−b|−|c−d|+a−c\neq 0$ almost surely?</p>
<p>I really want to believe this proposition is true but that is typically not enough to make it so.</p>
<h1>Ed... | g59265 | [
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0... |
<p>While doing multi-variate regression, i am encountering cases like below image, where for one of dimension, apart from couple of data points all values are same. Cause of this, model is going haywire.</p>
<p><img src="http://i.stack.imgur.com/G6NjO.jpg" alt="enter image description here"></p>
<p>What's right way t... | g59266 | [
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0.027199091389775276,
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0.0427... |
<p>Suppose we want to predict $Y$ given the following $X$ observations:</p>
<pre><code>x = c(abs(rnorm(2500, 0.1, 0.25)), abs(rnorm(2500, 0, 0.05)))
y = (x^0.35) + rnorm(length(x), 0, 0.25)
x = c(x, -x)
y = c(y, -y)
</code></pre>
<p>Clearly we have an exponential relationship between the predictor $X$ and $Y$. It's m... | g59267 | [
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0.08717284351587296,
... |
<p>As Kernel PCA is the same as PCA in higher dimension space, shouldn't the eigenvectors obtained be orthogonal?</p>
<p>Suppose, I have $n$ data points and let $a$ and $b$ be two eigenvectors of covariance matrix of mapped data, and $\alpha \in \mathbb{R}^n$ and $\beta \in \mathbb{R}^n$ be the corresponding eigenvect... | g59268 | [
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0.015222012996673584,
0.012070797383785248,
0.006023813039064407,
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0.0749... |
<p>I'm comparing the following 4 estimators of location of the Cauchy distribution:
Let $x_{1},..x_{n}$ be observations and $l$ be the log likelihood function.</p>
<p>$x=median(x_{1},..x_{n})$, $y=x+\frac{l'(x)}{n/2}$, $z=mean(x_{1},..x_{n})$ and $s=MLE$</p>
<p>I did simulations in R of the mean squared error and pro... | g59269 | [
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0.010235046036541462,
0.0731586292386055,
0.057... |
<p>I have a segmentation problem that using two different models I can assign a probability to each pixel of the image to be a background part. Two models produce slightly different results. Some pixel may have zero probability using one model, but have some value using the other model. But the idea is try to combine t... | g59270 | [
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0.09015271067619324,
-0.023657701909542084,
0.025406472384929657,
0.01550960... |
<p>The rpart() function in R returns cptable that includes columns xerror and xstd.
Here is an arbitrary example.</p>
<pre><code> CP nsplit rel error xerror xstd
1 0.161992664 0 1.0000000 1.0002790 0.01853630
2 0.043985638 1 0.8380073 0.8385070 0.01749290
3 0.030278222 2 0.7940217... | g59271 | [
0.037061791867017746,
0.009046660736203194,
-0.007969846948981285,
-0.029983067885041237,
0.04240812733769417,
-0.0371042899787426,
0.057757120579481125,
0.020060351118445396,
-0.030817292630672455,
-0.007095393259078264,
0.03325771540403366,
0.005728897172957659,
0.031263530254364014,
0.0... |
<p>I want to cluster photos and map them to places.</p>
<p>As input I have</p>
<ul>
<li>Photos with locations (lat, long)</li>
<li>Places - some as (imprecise) bounding boxes, some just as points, maybe others as bounding geometries</li>
</ul>
<p>However, all are not exact - photos relating to a building will be tak... | g59272 | [
-0.015974584966897964,
0.02723957598209381,
0.016500601544976234,
0.015436236746609211,
-0.001169737777672708,
-0.03740003705024719,
0.008488910272717476,
0.050514474511146545,
-0.00012175107258372009,
-0.016627168282866478,
0.01830131746828556,
0.004863665904849768,
0.11318325251340866,
0... |
<p>Imagine I have a random variable $X$ drawn from the sample space $S$ such that $Prob[X = x] = p_x$.</p>
<p>Let $A \subseteq S$ be a subset of values from the sample space. My question is if we have a lower bound for the maximum value of $\sum_{x \in A} \frac{p_x}{|A|}$, maximizing over all subsets of $S$.</p>
<p>... | g59273 | [
0.009964155033230782,
0.022206973284482956,
-0.03293111175298691,
-0.02256566658616066,
-0.0500473789870739,
-0.01518027950078249,
-0.05953444540500641,
0.01938306726515293,
-0.0371929369866848,
-0.05396623536944389,
-0.01601879671216011,
0.01418127678334713,
0.0515277273952961,
0.02814937... |
<p>1) If we use the formula</p>
<p>$$r = \displaystyle \frac{\displaystyle\sum_{i=1}^n \left( x_i - \bar{x} \right) \left( y_i - \bar{y} \right)}{\sqrt{\displaystyle \sum_{i=1}^n \left( x_i - \bar{x}\right)^2 \cdot \sum_{i=1}^n \left( y_i - \bar{y}\right)^2}}$$</p>
<p>for calculating $r$ we get $r = \frac{0}{0}$.</p>... | g59274 | [
0.015920564532279968,
0.005709078628569841,
-0.038107819855213165,
-0.01103182416409254,
0.011189202778041363,
-0.003649742342531681,
0.05032780021429062,
-0.03526444733142853,
-0.012504090555012226,
-0.01622484065592289,
-0.024285290390253067,
0.01787283830344677,
-0.0398009791970253,
0.0... |
<p>At this moment I have a dataset with 4000 samples (50% positive and 50% negative). Normally I would do cross validation for this approach, however besides normal data mining techniques I am also trying an alternate ILP approach. </p>
<p>Since I can't implement cross validation using the ILP system I am using, to ... | g59275 | [
0.0016738680424168706,
0.0028149671852588654,
-0.015042804181575775,
-0.07051809877157211,
-0.03533555939793587,
0.037387359887361526,
0.029761679470539093,
0.05577332526445389,
-0.0021739571820944548,
0.014676759950816631,
0.02669481933116913,
-0.031045114621520042,
-0.017939915880560875,
... |
<p>I've been working with the scipy gaussian kde implementation (<a href="http://docs.scipy.org/doc/scipy-0.13.0/reference/generated/scipy.stats.gaussian_kde.html" rel="nofollow">here</a>), but I don't quite understand the difference between the bandwidth factor and the covariance matrix. I'm using it for a single dime... | g59276 | [
0.011122732423245907,
-0.005476959049701691,
-0.0028139653149992228,
-0.07408754527568817,
0.0009763558045960963,
0.036848846822977066,
0.044893745332956314,
0.02551862597465515,
-0.03198319301009178,
-0.028038684278726578,
0.04476400837302208,
0.0027569709345698357,
0.027856621891260147,
... |
<p>I am working on a logistic regression model that attempts to predict the probability that individuals will do a certain activity, where each individual can be described by a number of categorical variables. In other words,</p>
<p>$$ \log\left(\frac{y}{1-y}\right) = X\beta + \epsilon$$</p>
<p>where $y$ is a binary ... | g59277 | [
-0.06072256714105606,
0.021067973226308823,
0.011906217783689499,
-0.0031033125706017017,
0.050537995994091034,
-0.08422929793596268,
-0.009900715202093124,
-0.04102098569273949,
-0.05007617175579071,
0.004712897818535566,
-0.038309186697006226,
0.021680451929569244,
0.024911118671298027,
... |
<ol>
<li>independence</li>
<li>homoscedasticity</li>
</ol>
<hr>
<p>This question is from an online quiz with one "correct" answer, but I'm not sure I agree. I understand that the answer is homoscedasticity, but isn't independence violated here as well? Since heteroskedasticity indicates that residuals are correlated ... | g59278 | [
0.02300121821463108,
-0.023098180070519447,
0.010232781991362572,
0.02993139997124672,
-0.02112593688070774,
0.0340275838971138,
-0.000966149615123868,
0.012957926839590073,
-0.05002494901418686,
-0.009767754003405571,
0.0006477563874796033,
0.03837969899177551,
-0.030153244733810425,
0.00... |
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