question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Maybe let me first describe the real world application of my problem before going to a more mathematical model.</p>
<p>Suppose I have a system that measures my current position up to an unknown error (let's say this would be a GPS-device). At every point that is recorded I also save the accurate position obtained b... | g7615 | [
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<p>I have a situation where we have a number of quantitative features / variables (p) than the number of samples (n). My objective is to classify these samples into groups (may be hierarchical). I can see a good discussion about this in this <a href="http://stats.stackexchange.com/questions/15564/clustering-of-10s-of-m... | g58591 | [
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<p>Suppose I have 64 columns that I have chosen out of 500+ columns based on the fact that they have the highest pairwise correlation (is this a good way?). I take 16 of these columns and run a simple multi-variate regression. I find that 4 of these columns have P values less than .05. Can I go back, do this for the... | g58592 | [
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<p>I have a question regarding which test I should run on some data. I have small groups of people who answered questions. The answers to these questions have been classified as correct or incorrect. The N of the total number of questions asked is fairly large, however, the N of the total number of groups is quite s... | g24803 | [
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<p>I am using the following example from the R manual: </p>
<pre><code># (2) Use the lmmlasso on a small simulated data set
set.seed(54)
N <- 20 # number of groups
p <- 6 # number of covariates (including intercept)
q <- 2 # number of random effect covariates
ni <- rep(6,N) # observations per g... | g58593 | [
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<p>Comparing ratings for recipes I have often wondered is, say, 50 reviews of average 4.5 better than 31 reviews of average 4.8?</p>
<p>Orbiting these considerations has been some idea of statistical significance. </p>
<p>All uncertainty threatens to be dispelled today since I decided to ask here. No doubt there is a... | g13718 | [
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<p>I am using the <code>dlnm</code> package to build a finite distribute lag linear model. I intend on testing the model-fit based on various lag levels to assess which lag is suitable. Needless to mention I will apply some domain knowledge to make a good call. I am using these two available resources to carry out this... | g58594 | [
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<p>I am currently fitting above mentioned functions to my data and I can observe, that both lognormal and Weibull are better fits than a power-law. In the literature it is often suggested that it is hard to distinguish these functions, but I can in my data.</p>
<p>I do not completely understand the differences between... | g13719 | [
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<p>Cohen's $d$ measures the difference between the mean for the experimental group and the control group divided by standard deviation. The Cohen's $d$ statistic produces something that does not add any value to the observed effect-size i.e. the difference between the mean for the experimental group and the mean of co... | g58595 | [
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<p>What's the difference between probability and statistics, and why are they studied together?</p> | g49865 | [
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<p>I have a random variable <code>X</code>.</p>
<pre><code>set.seed(1)
X <- rnorm(10,0,30)
</code></pre>
<p>I would like to generate three other variables <code>(y1, y2, y3)</code> that have a pre-specified R^2 of <code>.50</code>, <code>.36</code> and <code>.26</code>.</p>
<p>i.e: <code>cor(x,cbind(y1,y2,y3))^2=... | g4952 | [
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<p>I am collecting textual data surrounding press releases, blog posts, reviews, etc of certain companies' products and performance.</p>
<p>Specifically, I am looking to see if there are correlations between certain <em>types</em> and/or <em>sources</em> of such "textual" content with market valuations of the companie... | g58596 | [
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<p>I developed a composite score by converting four items to z-scores, then I summed up the z-scores to form a composite measure. </p>
<p>However, when I've calculated means to compare finding for two different groups on a couple datasets using this composite score, the mean scores are the same distance from zero. </p... | g13722 | [
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<p><strong>Edit</strong></p>
<p>I have found a <a href="http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281995%29123%3C2251%3ATIODSU%3E2.0.CO%3B2" rel="nofollow">paper</a> describing exactly the procedure I need. The only difference is that the paper interpolates monthly mean data to daily, while preserving the ... | g58597 | [
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<p>I have some queries I would like to discuss, I am doing some analysis for sensitivity. I am not from the field of statistics. I work with RNA-Seq data. The thing is I have found some genes which are differentially expressed by 4 different methods at different replicates. Out of which one of the method is our own dev... | g58598 | [
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<p>Are there any difference in beta coefficients when doing several multiple regression analysis as compared to doing multivariate regression?</p> | g13723 | [
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<p>First off, a very similar <a href="http://stats.stackexchange.com/questions/10419/what-is-theta-in-a-negative-binomial-regression-fitted-with-r">question has been asked before</a>. But the answers to this question did not explain what high/low values of theta mean. Here's my crack at trying to figure out what high/l... | g58599 | [
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<p>I'm interested in various methods of measuring dispersion of vectors mainly for use in cluster analysis. I can think of three methods: </p>
<ol>
<li>Find the mean vector (centroid), then calculate the variance of the distances of all vectors to this mean vector. It is possible that the set of vectors could all be ... | g58600 | [
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<p>In order to find an optimal time for initiation of treatment post surgery (oncologic patients) I created a ROC curve with death defined as event.
The AUC was not significant. However, I decided to use the time that provided the best specificity and sensitivity in cox regression as a binary variable.
The Cox paramete... | g58601 | [
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<p>I have 10 years of daily returns data for 28 different currencies. I wish to extract the first principal component, but rather than operate PCA on the whole 10 years, I want to rollapply a 2 year window, because the currencies' behaviours evolve and so I wish to reflect this. However I have a major problem, that is ... | g49315 | [
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<p>Let's say I got a set of models $M = \{M_1, M_2, \dots M_n\}$. </p>
<p>Now say I got some data $x$ and I would like to know, which model represents the data best.</p>
<p>I know how to calculate the likelihood $L(\theta | x)$, with $\theta$ being the parameters of any of those models. I realize that the likelihood ... | g13728 | [
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<p>I have a feature vector of size nx3 where n = no. of data points and no. of features = 3.<br>
So the mean is a 3x1 vector.</p>
<p>The data actually is a set of pixels of an image segment(not a whole image). and the 3 features are R,G,B for the time being(, although it can be anything).</p>
<p>My goal: To define a ... | g13729 | [
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<p>I just want to make sure I have something clear in my head. When I calculate the effect size for a paired samples t-test after obtaining a significant result, I simply take the mean of the differences divided by the standard deviation of the differences to get an effect size d. Do I then need to take d and divide it... | g13730 | [
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<p>I have been trying to look for a reference on the theory behind using the F-test to test for the equality of regression coefficients. The closest I could find is this, which is for general linear restrictions: <a href="http://www.mattblackwell.org/files/teaching/ftests.pdf" rel="nofollow">http://www.mattblackwell.or... | g58602 | [
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<p>My statistical learning text claims that for best subset selection, 2^p total models must be fit through regression if for p covariates, we fit p choose k models at each k, k = 1,...,p. I interpret this mathematically as 2^p = p choose 1 + ... + p choose k. Why 2^p models?</p> | g58603 | [
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<p>I have the following data for 200 cases/subjects:</p>
<ul>
<li>time to death over a 15 year period, $t$. A datum with a value of 180 months means that the subject did not die over the 15 year period.</li>
<li>the frequency of three particular types of event associated with each subject $a_{i}$, $b_{i}$ and $c_{i}$,... | g58604 | [
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<p>I have been trying to use the vars package in r for my multivariate time series data. I am having some problems. Do I have to do something to my multivariate data before using the vars package? Can someone help me with examples. Thank you.</p>
<p>Sam</p> | g171 | [
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<p>I conducted a pre and post survey that consisted of five questions with answers being either agree or disagree. The survey was to assess if a persons perception of Pit Bulls was improved after they interacted with it. </p>
<p>The first or pre survey was before the individual interacted with the dog. After they did... | g58605 | [
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<p>I would like to construct predictions for a mixed model (logistic via glmer) on a new data set using only the fixed effects, holding the random effects to 0. But I am having trouble setting up the model matrix to be able to calculate them.</p>
<p>Since the mer class doesn't have a predict method, and since I wan... | g58606 | [
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<p>I have this time series dataset: </p>
<p><img src="http://i.stack.imgur.com/eXXhd.png" alt="enter image description here"></p>
<p>The graph shows trend lines for 7 stock prices. They are very close and overlapping, but you will be able to get an idea that trend lines are layered (i.e. brown on the top and red/oran... | g58607 | [
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<p>I have customers which book an offer about once a year. I'd like to determine if there is a "loyality effect" - i.e. a customer from this year is more likely to book next year again.</p>
<p>I can see that after booking this year, a customer will most likely book either about one year later, or next January. Moreove... | g58608 | [
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<p>I want to generate random monthly <em>(m)</em> temperature (<em>T</em>) and Precipitation (<em>P</em>) data considering that both variables are intercorrelated (<em>rTP[m]</em>)
The tricky thing is that my random variables that have specific quantitative properties: temperatures are normally distributed, while preci... | g58609 | [
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<p>Just attended Andrew Ng’s online course on ML and although I’ve understood the methods I seem to be missing the intuition on where to apply them in terms of classification problems. </p>
<p>What are the pros and cons of each method and in which situation should I chose one over the others?</p>
<p>From the course I... | g58610 | [
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<p>I'm beginner in datamining.
I will do datamining projects, tasks as data modeling(run different dm algorithms), preprocessing(ETL,complex SQL quieries).
Is it sufficient for that tasks to use ordinary notebook(I consider quadcore i7 2ghz, 16GB ram, 256ssd -however dm desktop tools as spss,sass doesn't work in mac, b... | g49533 | [
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<p>I am using association rules for a classification problem. I am trying to predict tags for short pieces of text. What I am trying to do now is tune the confidence and support parameters in my association rules so that I am only using the rules that produce the best classification performance in an out-of-sample te... | g13738 | [
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<p>Hi I need help interpreting the confidence intervals in regards to this study done on a botanical medication to treat ADHD vs a placebo. The study used the ADHD Rating Scale-IV (range, 0-52)</p>
<p>"Inattentiveness improved 2.6 points (95% confidence interval, -4.6 to -0.6 points) with St. Johns Wort vs 3.2 points ... | g49534 | [
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<p><strong>The question in short</strong></p>
<p>I run a robust regression in R and made a boxplot with only one of the predictor variable grouping the response variable. On this boxplot I'd like to add some information about the statistical model. What information (and how to display it (it is not an issue of program... | g58611 | [
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<p>I want to come up with predictions of final energy demand per capita (fe) for a panel of countries. Explanatory variables are GDP per capita (gdp) and population density (pop) -- all variables are expressed in natural logarithms. I use <em>R</em> and the <em>plm</em> package for estimation.</p>
<p>My model is based... | g58612 | [
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<p>It seems like for managing with ordered measurements researchers <strong>usually</strong> deal with <a href="http://en.wikipedia.org/wiki/Polychoric_correlation" rel="nofollow">Polychoric Correlation</a>. (For example, for making matrix before doing Factor Analysis.) Why so?</p>
<p><a href="http://en.wikipedia.org/... | g58613 | [
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<p>If my data are non-normally distributed and I'm conducting a 2x2 ANOVA, what can I do to correct for this problem so I can report the main effect and interaction output appropriately? </p>
<p>Only one finding is significant (one of the main effects). I've read that bootstrapping cannot be applied to a univariate A... | g429 | [
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<p>For some research I am conducting, I have run into the following problem, which I must solve repeatedly:</p>
<p>My data consists of sequences of observations $\{O_1,O_2,\ldots,O_n\}$, each with a different normally distributed error. The sequences are variable in length, ranging from 5 to 44 observations.</p>
<p>... | g58614 | [
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<p>I would like to know the difference between panel data analysis & mixed model analysis. To my knowledge, both panel data & mixed models use fixed & random effects. If so, why do they have different names? Or are they synonymous?</p>
<p>I've read the following post, which describes the definition of fixe... | g58615 | [
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<p>I need to show that BMI of adults is neither age nor gender specific. Should I do ANCOVA or randomly make age groups and do two way ANOVA?</p> | g58616 | [
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<p>I've been given a task with the following question: </p>
<ol>
<li>Investigate whether or not the type or treatment (0 or 1) has an impact on the result (0 or 1) </li>
<li>The same as 1), but keeping in mind another variable which is either 0,1 or 2 may be a confounder for the result. </li>
</ol>
<p>How would I ... | g13741 | [
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<p>I'm trying to determine a smoothing parameter for the Hodrick-Prescott filter. I've seen that there are papers on the topic but they are far too advanced for my comprehension. If I have a data set, $X$, what are the steps to take?</p>
<p>My data is hourly. Using MATLAB I know the smoothing parameter values for mont... | g58617 | [
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<p>I've got a distance matrix between examples. I want to cluster them into <em>m</em> clusters with a nearest neighbor algorithm which works like this:</p>
<pre><code>1. Set i = 1 and k = 1. Assign example x_1 to cluster C_1.
2. Set i = i + 1. Find nearest neighbour of x_i
among the patterns already assigned to cl... | g42702 | [
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<p>I would like to know if there is any limitation in the size of the groups when you are implementing non-parametric permutation tests. My case belongs to the realm of medical imaging. I am comparing one patient image versus a group of control images. </p>
<p>For each image (including the patient's), I calculate a ma... | g13743 | [
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<p>What are the benefits of getting a PhD vs a masters in biostatistics (besides being a professor)? Will the first job will be the same for both levels? Does the PhD in biostatistics really make a difference in industry?</p> | g58618 | [
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<p>The empirical Bayesian method is a new concept to me. It raises my interest, because it offers a different philosophical and methodological perspective of statistical analysis.</p>
<p>From my limited knowledge, I am not sure if it is useful/powerful, or inferior to alternative methods, and if it is worth learning ... | g5049 | [
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<p>I'm designing a pretty simple experiment that goes like this. Participants will be shown a series of stimuli and after viewing each one they will answer a few questions where they will make judgments about the stimulus - all Likert items. There are two kinds of stimuli. Probably obvious, but the hypothesis is that t... | g13747 | [
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<p>I am looking for some advice for a colleague who is dealing with regression models for which it is know, that the continuous covariate of interest $X_1$ was measured with error. More precisely, we know only know that the true $X_1$ lies within an interval $(X_L, X_R)$. </p>
<p>My first idea was to illustrate/descri... | g5056 | [
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<p>I'm looking at a dataset that has pre-post test measurements on users' stress, depression and anxiety levels collected from a website's online health assessment. On average, the healthier participants at baseline got worse over time, and the sicker participants at baseline got much better, and the middle group gets ... | g58619 | [
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<p>I am a TA for a stats course for engineers, and I had a really good question from a student today, which I don't know the answer to.</p>
<p>We were going through the following word problem:</p>
<p>"4 computers run continuously for the Toronto Stock Exchange. The probability of a computer failure in a day is estima... | g13750 | [
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0.042... |
<p><strong>TLDR</strong>: How can I perform inference for the between group differences in a possibly logistic growth with time in the presence of outliers, unequal measurement times and frequency, bounded measurements and possible random effects on individual and per study level?</p>
<p>I am attempting to analyse a d... | g58620 | [
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0.... |
<p>I'm not too familiar with survival analysis, so this may be a somewhat basic question. </p>
<p>I am interested in the time between two events [$A$ - medication] and [$B$ - time of first treatment], the latter which can be equal to $A$. Specifically, I want to know if this varies across years. </p>
<p>The subjects ... | g58621 | [
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<p>I am reading conflicting references regarding the <a href="http://en.wikipedia.org/wiki/Fisher_consistency" rel="nofollow">Fisher consistency</a> of the sample variance. </p>
<p>$$s^2 = \frac{\sum_i^n (x_i - \bar{x})^2}{n}$$</p>
<p>Could anyone explain me how to proof whether $s^2$ is Fisher consistent or not? The... | g58622 | [
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... |
<p>I am having trouble in understanding <a href="http://rullf2.xs4all.nl/msct/node28.html" rel="nofollow">link</a> how the 5.4 has come from and the line </p>
<p><strong>" Since the distribution has to be equal to 1 at $r_u$, it must be divided by $\tilde{\phi} \exp (-d \tau K_{2}) r_u^{\nu}$"</strong></p>
<p>what do... | g58623 | [
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<p>As far as I know you can do a F-test ($F = s_1^2/s_2^2$) or a chi-squared test ($\chi^2 = (n-1)(s_1^2/s_2^2$) for testing if the standard deviations of two independent samples are different. But does this also hold for dependent samples?</p> | g13767 | [
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<p>I have developed a predictor which scores a datapoint, $x$ on how likely it is to belong to a particular class, $C$. The higher the score the more likely it is that the datapoint belongs to the class. </p>
<p>The predictor takes as input a number of other datapoints (as training data).</p>
<p>Typically I might hav... | g58624 | [
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<p>I want to interpret an interaction. Usually a conditional regression analysis is done with 1 SD below/above the mean (see Aiken & West, 1993, p. 18). My result is a contrast with $p=.068$ if I take 1.5 SDs $p=.044$. with 2 SDs $p=.033$. </p>
<p>It seems that contrasts get stronger by increasing values the numbe... | g13770 | [
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... |
<p>I am in a need of solving such problem: I have two data sets: number of people passing nearby some point in space (two points were analysed) and the function of buildings around those points. How do I find the correlation (or test if influence exists) of building functions to number of people passing by. For example... | g58625 | [
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<p>We toss a fair coin.</p>
<p>If a head appears then $X\sim N(0,1)$.</p>
<p>If a tail appears then $X=1$ with probability $1$.</p>
<p>Find the unconditional CDF of $X$ and plot it.</p> | g58626 | [
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0.0067017823457717896... |
<p>I am trying to conduct an EFA with a sample size of 150 respondents. I would also like to use cross-validation but my professor says that the sample is not big enough for that. Is that true?</p> | g58627 | [
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0.011575805954635143,
0.02576524205505848,
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0.024713600054383278,
0.0051276... |
<p>Let us consider the configuration of a 2D system and the standard definition of entropy $H=-\sum_{i=1}^{m}p_{i}\cdot \log(p_{i})$. Let us suppose that I can describe the state of my system by a 2D distribution over a square grid and suppose to consider two configurations (i.e. two distributions over these square gri... | g13771 | [
-0.031423550099134445,
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-0.008157064206898212,
-0.01559118740260601,
0.026976225897669792,
0.041221342980861664,... |
<p>I was not able to find the formula to allow me to calculate the mean and the median survival time for a Gamma survival function.</p>
<p>Does anyone knows how to calculate these?</p> | g13772 | [
-0.041063155978918076,
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0.015382918529212475,
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0.017592208459973335,
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0.039491117000579834,
0.022446077316999435,
... |
<p>The <a href="http://vis.uky.edu/~cheung/courses/ee639/Hammersley-Clifford_Theorem.pdf" rel="nofollow">Hammersley-Clifford Theorem</a> tells us that the distribution of a <a href="http://deeplearning.net/tutorial/rbm.html" rel="nofollow">RBM</a> must be <a href="http://en.wikipedia.org/wiki/Gibbs_measure" rel="nofoll... | g13773 | [
0.01747822016477585,
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<p>Is the purpose of <a href="https://en.wikipedia.org/wiki/Latent_variable_model" rel="nofollow">latent variable models</a> to model causality, where the causes are not observable i.e. latent?</p>
<p>Are <a href="https://en.wikipedia.org/wiki/Latent_variable" rel="nofollow">latent variables</a> modelling causes of th... | g13775 | [
0.01773138716816902,
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0.0267208... |
<p>I ran a comparison where I estimated the parameters of a model using $S$ different methods several times. More specifically I simulated $M$ datasets $\boldsymbol{y}_1, \dots, \boldsymbol{y}_m$ from a model parametrized by $\boldsymbol{\theta}$, where $\boldsymbol{\theta}$ is $p$-dimensional. Then I have estimated th... | g58628 | [
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0.02776961959898472,
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0.0... |
<p>In standarizing the data for supervised classification, one can do the following:</p>
<p>1) Extract mean and variance for each feature from training, use it to standarize both training and testing data. 2) Compute the mean and variance for entire data, training and testing, and standarizing both with the same stati... | g58629 | [
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<p><em>This is mostly for fun and because I haven't found it on here. Hopefully nobody looks up the answer online for it ruins the challenge. Best answer will be chosen on who can solve this in their own way. If you look up the answer at least give it your own flavor.</em> </p>
<h2>Gambler's Ruin</h2>
<p>A gambler ha... | g58630 | [
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0.05501709133386612,
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0.053389016538858414,
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0.... |
<p>I am studying Machine Learning (SVMs), and I found this $||w||$ in front of me. I have not seen it again, and Google does not allow me to search for it. Does anyone knows what is $w$, what is $||w||$, how it is called, and why we need that?</p>
<p>Many thanks</p> | g58631 | [
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0.053307175636291504,
0.09214785695075989,
... |
<p>I need to create a sample of a given size from a population. However, the population is dynamic, that is, comes as a stream of items, and every item has a "time stamp" based on its location in this stream. I don't know beforehand how long is this stream, but I need that in the chosen sample, the time stamps will loo... | g13777 | [
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0.004... |
<p>Damgaard and Weiner in <a href="http://jacobweiner.dk/Site/Publications_files/Damgaard_Weiner_2000.pdf" rel="nofollow">Describing Inequality in Plant Size or Fecundity</a> discuss computing the Lorenz asymmetry coefficient, S as well as confidence intervals for the estimates of S for a sample. </p>
<p>D A Seekell, ... | g58632 | [
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0.030276328325271606,
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0.0740693062543869,
0.06000... |
<p>I know that the beta weight tells you the relative importance of a predictor (IV) in predicting the criterion (DV). </p>
<p>However, is it true that beta weights can not be compared across different samples? (i.e. if I run two different regressions, both with the same independent variables, but different dependent ... | g58633 | [
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0.04033389687538147,
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... |
<p>I'm doing a lot of work on the Wikipedia page for this distribution:</p>
<p><a href="http://en.wikipedia.org/wiki/Dirichlet_compound_multinomial_distribution" rel="nofollow">http://en.wikipedia.org/wiki/Dirichlet_compound_multinomial_distribution</a></p>
<p>The actual name of the page is "Multivariate Pólya distri... | g43390 | [
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<p>Currently working on big data sets, I would like to fit a SARIMAX model to it in order to forecast future values. Here are my questions :</p>
<p><strong>Q1.</strong> As a matter of information, does anybody know how does R compute the fitting of an ARIMA/SARIMA model ?</p>
<pre><code>themodel = arima(auch[0:700,1]... | g58634 | [
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0.0019260273547843099,
0.026186073198914528,
0.04418250918388367,
0.05980634689331055,
-0.... |
<p>While studying for my stats course, I was trying to understand the difference between one-tailed and two-tailed hypothesis tests. Specifically, why does the one-tailed test reject the null while the two-tailed one does not? </p>
<p>An example:</p>
<p><img src="http://i.stack.imgur.com/sFoAx.png" alt="the differenc... | g49920 | [
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0.02117641270160675,
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0.010932073928415775,
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-0.07314570248126984,
0.01357704121619463,
0.03825821727514267,
0.0368829183280468,
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<p>I want to compare data that proportions among three different groups e.g.:</p>
<pre><code> ID Group Prop.Nitrogen
1 A 0.89
2 A 0.85
3 B 0.92
4 B 0.97
</code></pre>
<p>Following Wharton and Hui (doi:<a href="http://dx.doi.org/10.1890/10-0340.1">10.1890/10-0340.1</a><a href="http://dx... | g58635 | [
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<p>When doing principal components it is intuitively clear that noise accumulates more towards the last components. What would be the formal explanation of how and why this happens? </p> | g58636 | [
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<p>Asymptotic results cannot be <em>proven</em> by computer simulation, because they are statements involving the concept of infinity. But we should be able to obtain a sense that things do indeed march the way theory tells us. </p>
<p>Consider the theoretical result
$$\lim_{n\rightarrow\infty}P(|X_n|>\epsilon) =... | g58637 | [
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... |
<p>I'm looking for difficult Bayesian inference problems to test out different Monte Carlo sampling methods. I've mostly been looking at Hamiltonian Monte Carlo based algorithms and in particular, I've been using the trick of using the hessian at the Maximum A Posteriori point for the mass matrix.</p>
<p>What are some... | g58638 | [
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... |
<p>Suppose a grant program allows city administrators to allocate the grant across three mutually exclusive categories <code>1, 2, 3</code>. </p>
<p>City administrators are surveyed to elicit their preferred allocations. A response by administrator <code>i</code> is a triplet <code>R_i = (p1, p2, p3)</code>, where b... | g58639 | [
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<p>I am interested in the definition of quartile that is usually used when you're in basic statistics. I have a Stat 101 type book and it just gives an intuitive definition. "About one quarter of the data falls on or below the first quartile..." But, it gives an example where it calculates Q1, Q2, and Q3 for the set... | g43448 | [
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<p>In my specific case, I am measuring the mean of a sample for different values of a factor (let's say the possibilities are integers from 1 to 100). I have very good reason to expect the mean of each sample to be roughly proportional to the value of the factor; in any case, related values for the factor should give r... | g13782 | [
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0.032971784472465515,
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<p>Suppose we fit a proportional odds model to some data with $Y$ the response variable being ordinal. If we get 0 estimated for all the coefficients (except the intercepts), what does that mean? How would we interpret the model?</p> | g58640 | [
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<p>I've been trying to analyse data from a factorial design with missing cells without much success until now. I'm using Anova from car package, that, according with I've read, can handle unbalanced data with type III sum of squares. But when I detect an interaction effect I don't know how to unfold the degree of freed... | g43462 | [
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<p>I am working with a panel data and want to perform a regression analysis (OLS, fixed effects model or random effects model). The panel data is unbalanced with $T$ varying from 7 to 13, and $N=11$. I am confused about having a small number of observations (around 100). </p>
<p>What is the minimum time observations a... | g58641 | [
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0.019... |
<p><strong>Note:</strong> <em>I am posting a question from a former student of mine unable to post on his own for technical reasons.</em></p>
<p>Given an iid sample $x_1,\ldots,x_n$ from a Weibull distribution with pdf
$$
f(x) = k x^{k-1} e^{-x^k} \quad x>0
$$
is there a missing variable representation and hence ... | g58642 | [
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0.06837267428636551,
... |
<p>$X_1, X_2, X_3, \ldots{}, X_n$, i.i.d., follow $\mathcal{N}(0, \theta^2)$, $\theta > 0$. </p>
<p>What are the UMVUEs (Uniform Minimum Variance Unbiased Estimators) of $\theta$ as well as $\Phi(\tfrac{1}{\theta})$, where $\Phi$ is the cumulative distribution function of $\mathcal{N}(0,1)$?</p> | g58643 | [
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... |
<p>Could someone provide overhead of the following model for training (With respect to input size or if there are any relevant parameters). Overhead I mean somewhat like asymptotic time complexity form. </p>
<ol>
<li>Multiple linear regression models (Least Sqaures)</li>
<li>Decision Tree (C 4.5 OR ID3)</li>
<li>K nea... | g42747 | [
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0.049502745270729065,
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... |
<p>Let $Y_i$ be the response and $X_i$ be the independent variables. Whenever I've seen a quantile regression specification they'll go:</p>
<p>$Q_{\tau}(Y_i | X_i) = a(\tau) + b(\tau) X_i$</p>
<p>Or, alternatively:</p>
<p>$Q_{Y_i}(\tau|X_i) = a(\tau) + b(\tau) X_i$</p>
<p>where $X_i$ is a vector of independent vari... | g42749 | [
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<p>Various hypothesis tests, such as the $\chi^{2}$ GOF test, Kolmogorov-Smirnov, Anderson-Darling, etc., follow this basic format:</p>
<p>$H_0$: The data follow the given distribution.</p>
<p>$H_1$: The data do not follow the given distribution.</p>
<p>Typically, one assesses the claim that some given data follows ... | g58644 | [
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0.015412... |
<p>When splitting attributes while constructing a decision tree, i can use information gain or information gain ratio to try and determine the best value to split the tree on.</p>
<ul>
<li>I'd use information gain when I have smaller numbers of distinct values (mostly nominal and ordinal values that are not continuous... | g58645 | [
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-0.029314175248146057,
0.03468693047761917,
0.012768914923071861,
0.026814064010977745,
... |
<p>I'm trying to find the probability of P5 having C1, C3, or C4. Here are the constraints of the problem.</p>
<p>C1 - C5: Are cards that can be held by 1 person.
P1 - P5: Are players that each have 1 card.
X means the person does not have the card.
O means the person has the card
? means it's unknown who has the card... | g13791 | [
0.03611177206039429,
0.008581637404859066,
-0.00427080737426877,
-0.0252697691321373,
0.04664028808474541,
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0.050056565552949905,
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-0... |
<p>For a machine learning class I am taking, on our first homework assignment we are given the following problem that has me stuck:</p>
<pre><code>Consider the following simulated data set:
set.seed(123)
n<-100
X<-runif(n)
Y<-rbinom(n,1,exp(0.5+X)/(1+exp(0.5+X)))
a) Find the Bayes' classifier
b) Construct a... | g13792 | [
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0.001032490050420165,
0.011874589137732983,
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0.024201584979891777,
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0.039002079516649246,
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0.06033682823181152,
0.07056338340044022,
0.029... |
<p>A question was recently posted to an listserve that I subscribe to asking (perhaps cynically?) when a Bayesian approach has been crucial to "getting the job done" in addressing questions in the field of ecology. I'm wondering, in general, about when a Bayesian approach has been essential to progress in a particular... | g13793 | [
0.03715885803103447,
0.007973074913024902,
0.04193000867962837,
0.001717537990771234,
0.0007874397560954094,
0.003307619132101536,
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0.012540461495518684,
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-0.013480756431818008,
0.022298401221632957,
-0.01709114760160446,
0.05470609292387962,
0.04... |
<p>The rho formula divides the covariance by SD of X and SD of Y. Does it result in a valid estimate of the true correlation (i.e., in the population)?</p> | g42753 | [
0.01737411879003048,
-0.00848796684294939,
0.0040984624065458775,
-0.031079024076461792,
-0.025074439123272896,
0.04055376723408699,
0.04881883040070534,
0.029622802510857582,
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0.020001856610178947,
-0.010477566160261631,
0.0181835126131773,
-0.02039395645260811,
-0.... |
<p>Assume I have kept track of the number of views per page and I want to show trending pages.</p>
<p>I am thinking about applying some statistical tests like Log-likelihood/chi-squared to detect breakthroughs from the popularity expectation. </p>
<p>Can somebody point me to some resources related to this matter? </... | g13796 | [
-0.031118901446461678,
0.07837209105491638,
-0.012594741769134998,
0.00707844877615571,
-0.030326230451464653,
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0.021149873733520508,
0.0009351796470582485,
0.004684277810156345,
-0.005650611128658056,
-0.007340413983911276,
-0.012224220670759678,
0.08056560158729553,
0... |
<p>I have a bunch of features that I would like to use for classification/machine learning and cluster analysis. Normally I use single point values or transformations of values for features and everything is fine</p>
<p>Now I would like to use a matrix as a feature. The matrix is probably going to be a fairly big (say... | g58646 | [
-0.03618733957409859,
-0.026397911831736565,
0.003047920297831297,
-0.055811379104852676,
-0.006677324417978525,
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0.02292722836136818,
0.06029270589351654,
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-0.03921488672494888,
0.024237284436821938,
0.04960702732205391,
0.09970789402723312,
0.017... |
<p>This is kind of a beginner level question. I want to know how to assess the performance of a model I have created.</p>
<p>Suppose that we have an identification system aboard a spaceship. The job of the system is to identify the objects detected by the sensors of the ship. For example, the sensors may detect astero... | g58647 | [
-0.015200694091618061,
-0.01514502801001072,
0.0009102929034270346,
-0.04314180836081505,
0.042288389056921005,
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0.057634659111499786,
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-0.000980461249127984,
0.029995763674378395,
0.03748118877410889,
0.09574762731790543,
0.04... |
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