question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I have some issues solving sparse linear equations $Ax = b$</p>
<p>My matrix $A$ is sparse with dimension of 5 million by 5 million. Actually, it is a combination of two matrices. One is tridiagonal and the other matrix has a bigger band. For example the $29450^{th}$ row has non zero diagonal entry. Plus non zero ... | 45,287 |
<p>I have large amounts of data about events and historical behavior (clicks, purchases etc) of users on a site. I would like to be able to correlate the inputs (like clicks, purchases, other events) with the outputs of interest (lifetime order value of customer etc).</p>
<p>Can I use the exact same math and process t... | 71,368 |
<p>I have data structured hierarchically in this way, where single observations ("Member") are grouped in larger groups:</p>
<pre><code>Major_group Member Sample1 Sample2 Sample3
GroupA Member1 5 0 2
GroupA Member2 3 4 10
GroupA Member3 ... | 71,369 |
<p>Let's suppose I have a time series data that I would like to regress $y$ on $x$ and $Time$. See below for the dataset.</p>
<pre><code>y x time
12 100 1
14 101 2
16 102 3
18 103 4
20 201 1
22 202 2
24 203 3
26 204 4
</code></pre>
<p><strong>Approach 1:</strong></p>
<p>One approach is to do a multiple ... | 71,370 |
<p>I have generated a L1 penalized Cox model using the <code>penalized</code> package in R. I used the <code>optL1()</code> function to generate the Breslow object (see below):</p>
<pre><code>fit <- optL1(surv.obj, penalized = ..., etc)
</code></pre>
<p>In the reference manual, it says the <code>fit$predictions</... | 71,371 |
<p>I have some data examining blog posts on different days. Basically, about 2000 news articles pertaining a certain topic were sampled and each blog post was given a positivity percentage score depending on the amount of positive words in the text (from 0 to 1). </p>
<p>This data was collected over a week. Therefore,... | 71,372 |
<p>First, thanks for the wonderful site.
Second, I am trying to use an ROC curves to check the reliability of some nondestructive testing of concrete slabs. As you may know, the Non-destructive tests(NDT) work same as any diagnostic system where the output either yes or no with some necessary transformation. I am plann... | 71,373 |
<p>I want to make a logistic model from my survey data. It is a small survey of four residential colonies in which only 154 respondent was interviewed. My dependent variable is "satisfactory transition to work". I found that of the 154 respondent 73 said that they have satisfactorily transited to work, while the rest d... | 71,374 |
<p>The text book first generates some 2-class data via:</p>
<p><img src="http://i.stack.imgur.com/rf6xF.png" alt="enter image description here">
<img src="http://i.stack.imgur.com/tXrP7.png" alt="enter image description here"></p>
<p>which gives:</p>
<p><img src="http://i.stack.imgur.com/OzIxZ.png" alt="enter image ... | 71,375 |
<p>I'm having a look at x-ray waiting times in an emergency department and how these relate to the day of the week and the time of day that requests are ordered. (want to know if patients have to wait longer for their x-rays on weekends and at night compared with day shifts).</p>
<p>The waiting times have a significan... | 71,376 |
<p>I'm working on a project to compare different approaches to time series modeling. In the model selection process, we perform residual analysis for the fitted models. For regression, we need to check the normality assumption in the residuals by performing Shapiro-Walk's test, or plotting QQ-plot, etc. Do we also need... | 71,377 |
<p>When trying to estimate the parameters of a known distribution, it might occur that the maximum likelihood estimator and the method of moment estimator don't work well when there's only one observation.</p>
<p>What are some good non-Bayesian alternatives to maximum likelihood estimators and method of moment estimat... | 32,789 |
<p>I plotted density function in R and under the plot is number of bandwith. What does this number mean?</p> | 71,378 |
<p>Recently I have been playing with linear regression for classification. For the binary case, it is straightforward. For the multiple case, I know there are issues with using this approach (like masking). However, I cannot fully understand how this masking arises. As understand in the multiple case one has to compute... | 71,379 |
<p>Are the RSS examinations worth doing as a way to learn more statistics? I have been working a physicist for most of my life so I'm a little bit loathed to pay to learn maths as I can usually get my head around new statistical methods as and when I need them. The problem I have is that I only use what I know about an... | 32,792 |
<p>I'm sorry if this question has been answered before. I have a dataset:</p>
<pre><code> -1.5 -1.8 -1.625
-1.25 -1.525 -1.675
-1.15 -1.35 -1.65
</code></pre>
<p>etc</p>
<p>Each column is a treatment, each number is a sample. I want to divide each treatment by another number of similar magnitude and u... | 32,793 |
<p>Objective: To predict time to event of a customer using R
I developed a Non parametric model but as per my understanding we cannot perform predictions from these models, so I have to build a model which can predict for any test data. I hope extended cox model will work for my case (we have time depended co variants)... | 71,380 |
<p>In a multi-classification problem, we define the <em>logarithmic loss function</em> $F$ in terms of the <em>logarithmic loss function per label</em> $F_i$ as:</p>
<p>$$ F = -\frac{1}{N}\sum_{i}^{N}\sum_{j}^{M}y_{ij} \cdot Ln(p_{ij}))=\sum_{j}^{M} \left (-\frac{1}{N}\sum_{i}^{N}y_{ij} \cdot Ln(p_{ij})) \right ) = \... | 71,381 |
<p>So, in the video lectures from Harvard's Statistics 110:Probability course that can be found on iTunes and Youtube, I encountered this problem.</p>
<p><a href="https://www.youtube.com/watch?v=JzDvVgNDxo8#t=566" rel="nofollow">https://www.youtube.com/watch?v=JzDvVgNDxo8#t=566</a></p>
<p>I tried to summaries it here... | 71,382 |
<p>I am interested in supervised pattern recognition problems where the the label associated with each pattern gives the probability of membership for each of the $c$ classes, rather than assigning each pattern unequivocally to a single class. This can arise because the (possibly human) oracle providing the labels is ... | 71,383 |
<p>Question about appropriate PCA/ EFA rotation method.
While I see that oblique rotation methods (e.g. promax) are suggested for correlated data (and I have correlated data) I see that the majority of researchers use Varimax rotation in PCA/ EFA. I intend to use factor scores in cluster analysis, where it is importan... | 32,800 |
<p>Suppose in the 2D space we have an array of points, and each point has a weighting factor, which is a float value ranging from 0 to 1. Each point also has a coordinate in the 2D grid. The following pseduo-codes show the property of the point:</p>
<pre><code>class Point
{
public:
float weightingFactor_; // [0,1... | 49,470 |
<p>I have three questions.</p>
<ol>
<li><p>I want to conduct a planned comparison in ANCOVA which compares three groups (n=2, n=7 and n=5) with two groups (n=11 and n=25). Is it ok to include the group with n=2 if I am only conducting a planned comparison as described above?</p></li>
<li><p>Is it ok to conduct an ANCO... | 71,384 |
<p>I have been looking through methods to convert z-scores to positive values, without taking absolute values and somehow taking the sign of the score into account (I avoided taking absolute value, because I want to differentiate between transformed value for z-scores with same magnitude but different sign). The z-scor... | 71,385 |
<p>I am currently trying to model an uniform arrival process within my simulation model. However, I can only model it by means of an interarrival time (I can let the model wait for a certain amount seconds). </p>
<p>I want to have:</p>
<p>$$G(x) = {1 \over F(x)}$$</p>
<p>where $ F(x) \sim U(a,b) $.
I started by usin... | 71,386 |
<p>Can someone explain the difference between type 1:4 sums of squares using examples with relatable variables?</p> | 71,387 |
<p>I measured response variable $Y$ at three levels of factor $A$ and four levels of factor $B$, $n=6$ reps/treatment. Results include</p>
<ul>
<li>$A$ has strong effects on $Y$.</li>
<li>$B$ has no effect on $Y$</li>
<li>There is no $A*B$ interaction</li>
</ul>
<p>I would like to report all three results (the second... | 43,654 |
<p>I want to run a t-test on two conditions tested repeatedly on the same population. I'm doing this via a python implementation of a related sample t-test (<code>scipy.stats.mstats.ttest_rel</code>).</p>
<p>The related sample t test requires my input arrays to have the same length. I do however have a number of misse... | 71,388 |
<p>Here is the question:</p>
<p>A claim is made that men from two income families earn less than men who are the sole income earners in their household:</p>
<p>To support this claim, data from a random sample of 22 married men was gathered. For this
sample, the mean and standard deviation of salaries for 11 married m... | 71,389 |
<p>So I have the equation </p>
<p>$$h(t) = 1 + vt - \frac{1}2 gt^2 \pm sin(\omega t) $$</p>
<p>to describe the motion of a flipped coin. It is just a kinematics equation with an angular component added to it, where $h$ is the height of the coin, $v$ is the upwards velocity of the coin, $\omega$ is the angular velocit... | 71,390 |
<p>Pardon me if this is a simple question, but I haven't found a great resource for this just yet.</p>
<p>Yes, I know that when possible, we should try to treat ordinal variables as categorical rather than continuous, but I have a particular application where being able to interpret the ordinal variable (parental educ... | 71,391 |
<p>How should I read the output of the function <code>ar</code> in R. For example, take this VAR model:</p>
<pre><code>library(tseries)
data(USeconomic)
US.ar <- ar(cbind(GNP, M1), method="ols",
dmean=T, intercept=F)
</code></pre>
<p>(from the book <code>Introductory Time Series with R</code> by Cowper... | 71,392 |
<p>I want to find hypothesis testing books with <strong>problem sets</strong> and answers covering the topics:</p>
<ul>
<li>Testing variance</li>
<li>Type 1 and type 2 errors</li>
<li>Test parameters for Poisson and binomial</li>
<li>Chi-squared test</li>
</ul>
<p>I want to be able to read the question and determine ... | 71,393 |
<p>I'm trying to interpret variance inflation factors using the <code>vif</code> function in the R package <code>car</code>. The function prints both a generalised $\text{VIF}$ and also $\text{GVIF}^{1/(2\cdot\text{df})}$. According to the <a href="http://hosho.ees.hokudai.ac.jp/~kubo/Rdoc/library/car/html/vif.html">he... | 71,394 |
<p>I am trying to replicate the calculation that SAS and SPSS do for the partial autocorrelation function (PACF). In SAS it is produced through Proc Arima. The PACF values are the coefficients of an autoregression of the series of interest on lagged values of the series. My variable of interest is sales so I calculate ... | 49,754 |
<p>I have heard of unbiased estimate and MLE of variance, and some about those of kurtosis. Are there general results about </p>
<ul>
<li><p>unbiased estimates of k-th order <a href="http://en.wikipedia.org/wiki/Central_moment" rel="nofollow">central moments</a>?</p></li>
<li><p>MLE of k-th order central moments?</p><... | 71,395 |
<p>I have some triangulated 3D meshes. The statistics for the triangle areas are:</p>
<ul>
<li>Min 0.000 </li>
<li>Max 2341.141 </li>
<li>Mean 56.317 </li>
<li>Std dev 98.720</li>
</ul>
<p>So, does it mean anything particularly useful about the standard deviation or suggest there are bugs in calculating it, when the ... | 71,396 |
<p>This question is similar to another question I had recently posted but I have a follow on.</p>
<p>In classical linear regression, we have </p>
<p>$$\hat{\beta } \sim N(\beta,(X^{T}X)^{-1}\sigma^2).$$ </p>
<p>Using this, one builds individual hypotheses of the significance of the coefficients, as done in the book ... | 43,669 |
<p>I have the following sorted data (sampling from parametric space [1,5]) with respect to their distances of parameter Theta. i.e.,
Let say N = 1000,</p>
<p>Theta : 1.1, 1.7, 1.9, 2.4, 2.8, . . . , 4.9</p>
<p>Distance : 0.2, 0.3, 0.5, 0.9, 1.1, . . . , 1.9</p>
<p>From literature I know that more than 3% (i.e.,... | 71,397 |
<p>The <a href="http://cran.r-project.org/web/packages/fUnitRoots/index.html" rel="nofollow">fUnitRoots</a> package considers <code>lag=2</code> as the default value in the <code>urzaTest()</code> function (Zivot & Andrews unit root test), while for the <code>ur.za()</code> function in the <a href="http://cran.r-pr... | 32,811 |
<p>I have the following logistic regression output:</p>
<pre><code>Coefficients:
Estimate Std. Error z value Pr(>|z|)
(Intercept) 0.5716 0.1734 3.297 0.000978 ***
R1 -0.4662 0.2183 -2.136 0.032697 *
R2 -0.5270 0.2590 -2.035 0.041898 *
</code></pre>
<p>Is it... | 43,670 |
<p>I have a number of multivariate observations and would like to evaluate the probability density across all variables. It is assumed that the data is normally distributed. At low numbers of variables everything works as I would expect, but moving to greater numbers results in the covariance matrix becoming non positi... | 71,398 |
<p>I am measuring the change in random effect (random intercept) over time by running models such as </p>
<p><code>glmer( bull~p1+p2+p3+p4+p5+(1|school),subset=(yr=2011),data=bull, family=binomial(link=logit))</code> </p>
<p>using different <code>subset=(yr=20??)</code> for each year. In the comments to my <a href="h... | 71,399 |
<p>I have a set of data on smoking patients and heart attack on different time points for 25 countries.</p>
<p>How can I calculate the correlation between the smoking patients and heart attacks for each country?</p>
<p>My data look like this table<a href="http://i.stack.imgur.com/bxEh2.png" rel="nofollow">1</a>:</p>
... | 32,816 |
<p>I was told that this hybrid is wrong and I should never use it for any serious writing:</p>
<pre><code>We estimated all of the ARMA models considered in this paper using the standard
procedure of maximum likelihood. We based model selection on the Schwarz Bayesian
Criterion, with the requirement that all paramete... | 71,400 |
<p>If I have a response vector that is mostly one class label, convergence of Lasso in <code>glmnet</code> will be extremely slow, for example:</p>
<pre><code> require(glmnet)
s <- matrix(rnorm(2000*1000),ncol=1000)
f <- rep(c(-10,0,10,20),2000)[sample(2000)]
f[200:2000] <- 0
fit <- glmnet(s,f,family='... | 71,401 |
<p>One naive method for approximating a normal distribution is to add together perhaps $100$ IID random variables uniformly distributed on $[0,1]$, then recenter and rescale, relying on the Central Limit Theorem. (<em>Side note</em>: There are more accurate methods such as the <a href="http://en.wikipedia.org/wiki/Box%... | 32,820 |
<p>I was thinking by using validation but not quite sure how to go with it. Please list some papers or ideas on how. This is for multiclass problem (using one vs all approach). I think each class/category has its own speed in converging to a good strong classifier hence would need different number of weak classifiers t... | 43,676 |
<p>I am currently trying to compute the BIC for my toy data set (ofc iris (: ). I want to reproduce the results as shown <a href="http://www.cs.joensuu.fi/~zhao/PAPER/ACIVS08.pdf" rel="nofollow">here</a> (Fig. 5). That paper is also my source for the BIC formulas.</p>
<p>I have 2 problems with this:</p>
<ul>
<li><str... | 71,402 |
<p>I am wondering if anyone has book references for time series. I would like something comparable (in popularity) to the 'ESL' or to 'Machine learning' from Murphy in the machine learning field. </p>
<p>Does anyone knows what are the most complete (in term of methods scope) books containing all about exponential smoo... | 32,823 |
<p>The p-value is said to be the probability of the respective event <em>assuming that $H_0$ is true</em>. The simplest possible toy example are two coin tosses. The 2-tailed $H_0$ would be that you consider the coin fair, $H_1$ in this case is that you consider it biased to one side or the other.</p>
<p>For one 1-tai... | 71,403 |
<p>I'm using the function <code>dlmGibbsDIG</code> (Gibbs sampler) in the <code>dlm</code>package from R to estimate the unknown variances. The output are the unknown variances together with the (saved) sampled states.</p>
<p>Then the <code>dlmFilter</code> function performing the kalman filter only need as arguments ... | 71,404 |
<p>I'm trying to create an algorithm that would detect link spam structures in directed graphs of nodes (converted to matrices). Each structure is represented by a sparse matrix of links between the central page and 2 levels of links. I was going to use neural networks, however the matrices that I have in my training s... | 71,405 |
<p>I'm trying to construct an error ellipsoid from a covariance matrix (which exists for a 3D point) and then sample consistent xyz points in this region. In a previous question when I asked about this (on math.stackexchange, <a href="https://math.stackexchange.com/questions/823329/incorporating-an-error-ellipse-from-e... | 32,826 |
<p>I have a list of cities that I want to compare in terms of their similarity. Each city can described by a large but finite number of characteristics but most of them will have missing data for some random number of characteristics. If I consider each city to be a n-dimensional vector with with missing data in some d... | 71,406 |
<p>When I normalize the weights I use for fitting a line with weighted least squares, the parameters of the fitted line and the 'normal' standard errors stay exactly the same, as I would expect.
The HC3 standard error estimates, however, change completely.</p>
<p>I get the feeling that I am missing something quite imp... | 32,827 |
<p>I have a regression model to estimate the completion time of a process, based on various factors. I have 200 trials of these processes, where the 9 factors being measured vary widely. When I perform a linear regression of the 9 factors (and all 2 and 3 factor interactions), with no explicit intercept, I get an adjus... | 71,407 |
<p>I am running different algorithms (SVM, Random Forest, other tree-based decision algos).</p>
<p>I noticed that my performance went down (error went up) after adding new features.</p>
<pre><code>performance(Feature_family_1 + Feature_family_2) < performance(Feature_family_1)
</code></pre>
<p>Is this possible, a... | 49,872 |
<p>I have read the Stata manual but I am still having trouble understanding how to interpret these results. I am looking to determine how each parameter affects the outcome given a 1-unit change.</p>
<p>The code I am using in Stata is as follows:</p>
<pre><code>probit hhaffbyinvest ///
femintmig femdommig maleintmig ... | 71,408 |
<p>can anybody tell me why the <code>oneway.test()</code> results in a p-value of NA when var.equal is set to FALSE but in a p-value of 0.7173 when it is set to TRUE</p>
<p>Here is my example:</p>
<pre><code>x <- c(3.921973, 5.703782, 3.921973, 3.921973, 3.921973, 6.075346, 3.921973, 3.921973, 3.921973, 3.921973)
... | 32,833 |
<p>In a survey, where students were presented various stimuli, after each stimulus they were asked to rate the following:</p>
<ul>
<li><strong>Quality</strong>, on a five-point scale from "Excellent" to "Bad", let's say $Q$</li>
<li><strong>Confidence</strong> in their quality ratings, on a four-point scale from "Very... | 71,409 |
<p>Dumb question but let's say that I have a continuous response variable and have constructed a regression model with multiple predictors. Most of my predictors are continuous but I have one which is a dummy variable. How do I determine whether the ols assumption of linearity is met or violated? And if the linearity a... | 71,410 |
<p>If you have a categorical variable with $k$ levels (so $k-1$ indicator variables), is there an easy way to calculate the odds ratio? Suppose the first level is the reference level. The model would be $$ \frac{p(x_{2},\dots, x_{k-1})}{1-p(x_{2}, \dots, x_{k-1})} = \text{exp}(b_0+b_{2}x_2 + \dots + b_{k-1}x_{k-1})$$</... | 71,411 |
<p>I have data on <code>alcohol use by drivers</code> as a binary response variable along with many other variables such as: </p>
<ol>
<li>Driver's age, gender and race </li>
<li>Passenger's (if present) age, gender</li>
<li>Location variables</li>
<li>Road characteristics</li>
</ol>
<p>Here is sample of the data:</p... | 32,838 |
<p>Recently I was very embarrassed when I gave an off the cuff answer about minimum variance unbiased estimates for parameters of a uniform distribution that was completely wrong. Fortunately I was immediately corrected by cardinal and Henry with <a href="http://stats.stackexchange.com/questions/33736/obtain-the-minimu... | 71,412 |
<p>We have a population of n=1000, nine binary responses (0 symptom absent, 1 present), and 2 timepoints. Note that some of the responses are heavily skewed, only 1% of the subjects are in the "symptom present" category at baseline for the most skewed response. </p>
<p>We calculate the change over time as ratio:
part... | 32,840 |
<p>I was reading an article that reported a Cronbach's alpha of .85 for a two-item scale. The scale was measuring self-perceived competence. Each item was on a 7-point Likert-type scale.</p>
<p>Intuitively, that seemed like quite a high Cronbach's alpha for a scale with only two items. </p>
<ul>
<li>Is it plausible t... | 32,841 |
<p>I would like to get the posterior simulations of the variance components of a lmer() model with the mcmcsamp() function. How to do ?</p>
<p>For instance, below is the result of a lmer() fitting :</p>
<pre><code>> fit
Linear mixed model fit by REML
Formula: y ~ 1 + (1 | Part) + (1 | Operator) + (1 | Part:Operato... | 71,413 |
<p>I am doing some inferential analysis on some ordered dependent variables (about 70). Their scales range from 4-10 possible (ordered) responses. To give some context, it's all social data--happiness, feelings towards minorities, etc.--and my inferential question is on the social returns to university degrees. </p>
<... | 71,414 |
<p>I'm reading Fawcett's 2004 paper on ROC graphs for machine learning algorithms, which can be found <a href="http://binf.gmu.edu/mmasso/ROC101.pdf" rel="nofollow">here</a>.</p>
<p>On page 7-8 he shows a simple ROC example and makes some interpretations that I don't understand. Below is the ROC graph:</p>
<p><img sr... | 71,415 |
<p>What is your favorite statistician quote?
This is community wiki, so please one quote per answer. </p> | 71,416 |
<p>I have KDD dataset for detecting fraud actions on networks but it has millions of lines and >20 feature columns. Thus it is not viable to process all these on my personal computer. I am thinking about the random sampling on data to reduce the rows to some legible numbers than I want also to reduce the number of feat... | 48,184 |
<p>I'm doing shopping cart analyses my dataset is set of transaction vectors, with the items the products being bought.</p>
<p>When applying k-means on the transactions, I will always get <em>some</em> result. A random matrix would probably also show some clusters.</p>
<p>Is there a way to test whether the clustering... | 32,845 |
<p>Assume that $c_{ij}(W)$ is a simple function of a random variable W. (This comes is Dynamic Programming where we are currently at node i and we want to go to node j in the shortest path problem and W is the random variable denoting the time that we wish to minimize)</p>
<p>What does the following expression mean?
$... | 71,417 |
<p>I have what feels like it should be a very easy analysis to work out, but I've been trying for hours and I can't figure it out.
I'm using SPSS by the way.
I have 10 (5 of each group) different binary response variables (yes/no) that I need to 'bin' into two different groups for comparison. Each subject answered each... | 71,418 |
<hr>
<p><strong>Method 1: Cluster by K-means with initial centroid {27, 67.5}</strong> </p>
<hr>
<p><strong>Method 2: Cluster by K-means with initial centroid {22.5, 60}</strong></p>
<hr>
<p><strong>Method3: Agglomerative Clustering</strong></p>
<hr>
<p>How can I know which method gives a more reasonable cluster... | 71,419 |
<p>According to the Central Limit Theorem (CLT) in statistics, the distribution of the average of randomly sampled n observations tends to follow normal distribution as the sampling size n becomes larger, even when the parent distribution from which the average is calculated is not normal. The distribution of the avera... | 49,873 |
<p>I would like to perform hierarchical regression in which all variables are based on previous research/theory. But when I perform Pearson correlations, I found that some variables did not correlate to the DV. Should I still include those non-significant variables in the hierarchical regression as suggested by previou... | 71,420 |
<p>I have a regression with my dependent variable being the number of visitors and my independent variable being the presence or absence of a certain kind of ad.</p>
<p>Now, when I run the regression my independent variable is significant. When instead, I add another independent variable (the presence of a big exhibit... | 71,421 |
<p>I'm reading about expectation maximization from Dempster, Laird and Rubin's original paper which can be found from the following link:</p>
<p><a href="http://web.mit.edu/6.435/www/Dempster77.pdf" rel="nofollow">http://web.mit.edu/6.435/www/Dempster77.pdf</a></p>
<p>My questions are from pages 1 and 2. I have added... | 71,422 |
<p>I am working on a project where the training labels are given to me as a probability value in the range [0,1]. My first approach was to fit a simple linear ridge regression to predict the probability. This isn't ideal as:</p>
<p>1) Predictions from this model end up with values outside the range of 0 and 1
2) I d... | 71,423 |
<p>I was reading the Hastie, Friedman, Tibshirani paper <a href="http://biostatistics.oxfordjournals.org/content/9/3/432.full" rel="nofollow">"Sparse Inverse Covariance Estimation with the Graphical Lasso"</a> and it had the following</p>
<p><img src="http://i.stack.imgur.com/915iR.png" alt="enter image description he... | 32,860 |
<p>I want to do a simple nearest neighbour calculation in Excel over a multivariate space to get an idea of how my data clusters. I have a set of data points $\{X_1, X_2, \ldots X_n\}$ and a set of possible cluster centers $\{M_1, M_2, \ldots, M_m\}$. Initially, I propose to simply use a weight vector $w$, and compute ... | 71,424 |
<p>I have three groups that I would like to match on age and gender. They don't need to be matched one-to-one, I just need group differences p < .05 for both variables. I can find packages that will match TWO groups, but not more than that. Does such a package or code snippet exist?</p>
<p>Secondarily, because the... | 37,864 |
<p>This is a very basic question about Bayesian inference. I'm not grasping one or more fundamental concepts.</p>
<p>Let's say I have two observed outcomes, <em>X</em> and <em>Y</em>. I want to infer the probabilities (<em>px</em> and <em>py</em>, respectively) of each occurring given <em>X</em> and <em>Y</em>. I do n... | 43,736 |
<p>At the moment I'm researching clustering of single words. The input of this research is a list of words (unigrams). During the research I want to compare several similarity algorithms to see how they impact the cluster result.</p>
<p>At the moment I’m using a 70word data set, where the words belong to 7 clusters (i... | 9,967 |
<h2>Image Similarity based on Color Palette Distribution</h2>
<p>I am trying to compute similarity between two images based on their color palette distribution, let's say I have two sets of key value pairs as follows,</p>
<p>Img1: <code>{'Brown': 14, 'White': 13, 'Black': 40, 'Gray': 31}</code></p>
<p>Img2: <code>{'... | 71,425 |
<p>I am writing with questions about a study I am helping with:</p>
<p>Two “raters” will score athletes subjectively from 0 to 3 (3>2>1>0) on each of 10 skill performances. Scores will be summed to a maximum of 30, and the total bracketed into approximately three categories for comparison with regard to knee injury i... | 71,426 |
<p>I am looking to fit a Cox proportional hazard survival model. Looking at the K-M curve (below) for one variable (with 2 categories) it appears there is a change in hazard ratios at around day 110. I was thinking of modeling this with a change-point model.</p>
<p><img src="http://i.stack.imgur.com/xZBjJ.png" alt="... | 32,866 |
<p>I am trying to estimate parameters for a Pearson III distribution using package "lmomco" (session information given at the end).</p>
<p>I have 40 precipitation values in vector "val.x". I estimate P3 parameters using the sequence of pwm.ub(), pwm2lmom() and parpe3() function calls (results for each are shown below... | 71,427 |
<p>Consider the following data set <strong>test</strong> with binary outcome variable <strong>z</strong> and predictor variables <strong>a,b,c</strong>. </p>
<pre><code> z a b c
0 1 40 185
0 1 25 128
0 0 32 100
0 0 29 100
1 1 30 107
0 0 30 133
1 ... | 71,428 |
<p>Suppose $X$ and $Y$ are independent. To be concrete, suppose $X$ is $N(0,a)$ and $Y$ is $N(0,b)$. For any scalar c,d with c < d, is there a way to bound the following probability from above in terms of a,b,c,d?</p>
<p>$P(cX<Y<dX)$</p> | 32,868 |
<p>I have been using PCA results and variable loadings on the factors generated to select original uncorrelated input variables for model making</p>
<p>I was putting what i thought were <strong>rotated</strong> factors from PCA into models and seeing what factors were significant. Then i would go back and see if i cou... | 9,991 |
<p>I’m trying to solve a SEM. Mi model includes 4 latent variables and 11 observed variables. My data is binary.</p>
<p><strong>Question 1:</strong> I just have 47 observations and in the literature a sample size over 150-200 is recommended. I understand that bootstrapping or Bayesian statistic may be used to deal wit... | 32,870 |
<p>Is there a way to perform multiple logistic regression on repeated measures data using Matlab?</p>
<p>I have a data set containing a daily measurement recorded from 20 participants for 60 days. I am calculating 18 features for each participant for each day.
I wish to determine if there is a relationship between eac... | 43,741 |
<p>I'm trying to compare three groups data. But the data set is about a new drug trial. The data set has these characteristics:</p>
<ol>
<li>Follow-up set. That is, after administration of the drug, a
series of parameters were collected in the following date, day0,
day1,day2,...,day28.</li>
<li>Unbalanced set. Because... | 71,429 |
<p>I have a data set where I test for significant differences between three populations with respect to some 50 different variables. I do this using Kruskal-Wallis tests, on one hand, and by likelihood ratio tests of nested GLM model fits (with and without population as an independent variable), on the other.</p>
<p>A... | 32,871 |
<p>Quite a while ago, I <a href="http://stats.stackexchange.com/questions/23633/interaction-term-as-a-dependant-variable-in-lmm-with-r">asked a question</a> for which <a href="http://stats.stackexchange.com/users/7972/peter-ellis">Peter Ellis</a> provided a very interesting answer. Now I'd like to follow on that and ha... | 32,872 |
<p>I've been struggling with the following problem with hopefully is an easy one for statisticians (I'm a programmer with some exposure to statistics).</p>
<p>I need to summarize the responses to a survey (for management). The survey has 100+ questions, grouped in different areas (with about 5 to 10 questions per area... | 36,640 |
<p>I am using <code>PROC LOGISTIC</code> along with <code>Class</code> statements to do binary logit model(default=1,non-default=0) on a bank loan dataset where I have 7 numeric independent variables and 1 categorical independent variable.</p>
<p>Hosmer and Lemeshow test yields a <code>p = 0.6757</code>, and <code>Per... | 32,873 |
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