question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>Let $X$ and $Y$ be independent $rv$ such that $XY$ is a degenerate $rv$. Can I say that individually $X$ and $Y$ are also degenerate? Why? thanks..</p> | 69,377 |
<p>I'm writing a script that analyses run times of processes. I am not sure of their distribution but I want to know if a process runs "too long". So far I've been using 3 standard deviations of the last run times (n>30), but I was told that this does not provide anything useful if the data is not normal (which it do... | 69,378 |
<p>I have some small datasets (example data given below) where I am interested in describing relationships between $Y_1$ and $Y_2$ across a gradient $X$ at two time points (date = "early" & "late"). As you can see from the first plot below, with $Y_1$, there appears to be a general increasing trend over across $X$... | 29,830 |
<p>I was talking with a colleague who told me that at the time of making logistic regression across a population did not have to worry about assumptions such as multicollinearity, because when analyzing the entire population estimated betas are "actual parameters" and since to "multicollinearity only affects the signif... | 34,371 |
<p>In my training set, I have 4026 instances, two classes and 104 attributes.</p>
<p>The training error (error on the entire training set) is about 14% and 10 fold CV error on the training set is about 27%.</p>
<p>Does this mean that my model is overfitting the training data?</p>
<p><strong>EDIT (More Results):</str... | 69,379 |
<p>I have two paired samples and I am running a paired Mann-Whitney test to determine whether they are different. In Matlab, this takes the form of p = signrank(x,y), which tests the null hypothesis that x-y comes from a population of median zero.</p>
<p>Unfortunately, Matlab doesnt give difference estimates for x-y o... | 29,831 |
<p>I have repeated measurements on several hundred subjects. I plan to fit a random intercepts model. Most subjects have 3 to 4 measurements but about 20% only have one measurement.</p>
<p>For the subjects with one measurement, should they share the same intercept or should they each have their own intercept as well... | 69,380 |
<p>I'm interested in conducting an individual patient data (IPD) meta-analysis in which the main outcome of interest is a correlation coefficient between and IV and DV.</p>
<p>The IV is measured slightly differently across studies, and conversion to make them all match might not be possible. Clearly, I can still do a ... | 69,381 |
<p>I have to regress the following equation in Stata:</p>
<p>$$R_{i,t} = \delta{i} + \sum_i \alpha_i*W_i + \sum_i \beta_i * R_{i,t−n} + \mu_{i,t}$$</p>
<p>I'm ok with this regression. My problem comes out when I have to regress the second regression of the model I'm studying, that is:</p>
<p>$$|μ_{i,t}| = \omega_i ... | 29,835 |
<p>I am doing some post-hoc comparisons (in lme4, but here I'll just present a simple linear model), and I am having a hard time making sure that I am building the right matrix of contrasts to test differences between some combinations of factors. </p>
<p><strong>Here is my model:</strong></p>
<pre><code>dataset <... | 24,052 |
<p>I recently took an introductory course on multilevel modelling. Most of the datasets and examples we used were from the social sciences. I've just got a 2 week internship in a biostatistics department, where they want me to start a project concerning the variation at hospital level of patient outcomes for an emergen... | 40,041 |
<p>I'll try to compute different similarity measures on some data. The result is always a similarity matrix on the data. </p>
<p>I want to evaluate the quality of the matrix by checking if the values for positive and negative similarities have a wide spread so that one can set an threshold which is very general to all... | 69,382 |
<p>I have counts of people with a condition, by age (5-year groups), sex, and area (100-200 areas).</p>
<p>For each area, I have:</p>
<ul>
<li>estimated population by age (5-year groups) and sex,</li>
<li>estimated population percent living in city, small town or rural (sum
to 100%),</li>
<li>estimated population in ... | 29,838 |
<p>Say I have N observations, possibly multiple factors and I repeat each observation twice (or M times) how would a regression on this new set of size NM compare to a regression on just the original observations?</p> | 40,045 |
<p>I have a high dimensional dataset (n*p: 30 * 100) which I want to use as an testing dataset to build a two group classifier (LDA or QDA). I've read that you can do PCA to do an dimension reduction of your dataset to select to most important features. But I'm a bit confused what you use exactly as the input to build ... | 69,383 |
<p>Let $\lambda \mu > 0$ and let $X$ be a Markov chain on $\{1,2\}$ with generators</p>
<p>$$
Q = \begin{pmatrix} -\mu & \mu \\ \lambda & -\lambda \end{pmatrix}$$</p>
<p>Write down the forward equations and solve them fro the transition probabilities, $p_{i,j}(t), i,j = 1, 2$.</p>
<p>The answers say:</p>
... | 69,384 |
<p>So far i have evaluated mn Bayes and Bernoulli, so my question is if i take the counts of the words of each document and use them for assigning the document to the particular class will it work with Multivariate Gaussian classifier (Bayes with Gaussian model)?</p> | 69,385 |
<p>Let's say A, B, C, D, E, F are classes of text documents (i.e. sentences). Usually they occur distinctively, say: one document is precisely C. But sometimes one document is C AND A, at the same time. Because A is more important than C, the document class is defined . So at least two questions arise:</p>
<p><em>1) H... | 69,386 |
<p>I am reading Chris Bishop's chapter on Expectation Propagation and there is the bit on how approximating factor graphs as shown in the images.</p>
<p><img src="http://i.stack.imgur.com/wkAVG.png" alt="enter image description here"></p>
<p>So, the original joint distribution can be written as:</p>
<p>$$
p(x) = f_a... | 29,841 |
<p>I work with medical imaging and have the following issue:</p>
<p>-- every time I scan a patient I obtain images of a calibration phantom alone, followed by images of subject + calibration phantom in the same image</p>
<p>Although the calibration phantom has a stable composition, measures of its density vary from s... | 69,387 |
<p>Imagine I have measured heights of humans (in cm) and show the data in a histogram:</p>
<pre><code># Generate sample data
sampleSize = 100000
sampleData = round(rnorm(n = sampleSize, mean = 175, sd = 14))
# Draw histogram of sample
h = hist(sampleData, breaks = max(sampleData) - min(sampleData), plot=T)
</code></p... | 36,141 |
<p>I have a table with each row representing single printer model, its features, and price. I want to know how price is formed based on these features. What should I start with? Multiple regression, so I could cut off insignificant features? Cluster analysis to define small clusters with equal price? What are the ways ... | 29,843 |
<p>I have dataset with large number of labelled data (say that there are <em>k</em> classes). I have also another, much smaller dataset with unlabelled data that I want also to be labelled. The problem is that in the second dataset, number of classes need not to be the same as number of classes in first dataset (more p... | 49,200 |
<p>I have a data set with my target gene and more than thousand transcriptional factors somehow correlated with this gene. There is data of these factors in more than 70 variable conditions. What I'm looking to do is use CV to find most useful variables which correlate with my target gene. How could I do that in R pl... | 40,052 |
<p>In the GBM package one is supposed to be able to provide interaction.depth>2, which means higher-order interactions between features.
However, the resulting trees (as seen by pretty.gbm.tree) never show such interactions (and indeed - each row corresponds to just a single feature).</p>
<p>I'm not even sure anymore... | 48,556 |
<p>I am analyzing a longitudinal panel dataset using OLS. The data spans around 40 years, but for some variables data was unavailable for certain categories. In most cases, the data for given category stretches not as far back as for others (or ends earlier), but there are also a few cases where a category has an entir... | 69,388 |
<p>I wish to run some simulations on the 'estimates' of an event provided by experts (or historical data if available).</p>
<p>For example: The technology manager of company X says that probably 300-1000 computers in the organization (out of say 100,000 in total) have Windows XP that needs to be phased out. </p>
<p>N... | 40,060 |
<p>I have found the article by <a href="http://stats.lse.ac.uk/fryzlewicz/uh/uh.pdf" rel="nofollow">Fryzlewicz (2007)</a> and his R package <a href="http://cran.r-project.org/web/packages/unbalhaar/unbalhaar.pdf" rel="nofollow">unbalhaar</a>.</p>
<p>I do not understand well the outputs of his functions and in particu... | 69,389 |
<p>Here is the article that motivated this question: <a href="http://www.washingtonpost.com/blogs/ezra-klein/post/does-impatience-make-us-fat/2011/10/10/gIQA1eMnaL_blog.html">Does impatience make us fat?</a></p>
<p>I liked this article, and it nicely demonstrates the concept of “controlling for other variables” (IQ, c... | 49,481 |
<p>I am working on finding higher order moments for a given theoretical function, to be used in modelling of daily log-returns. The PDF is, </p>
<p>$f_r(x) =$
$\begin{cases}
\quad \frac{1}{2}ae^{a\left(x-\mu\right)} & \text{if x } < \mu \\
\quad \frac{1}{2}be^{-b\left(x-\mu\right)} & \text{if x } \geq ... | 40,062 |
<p>I am given an exercise, and I can't quite figure it out.</p>
<blockquote>
<p><h3>The Prisoner Paradox</h3> Three prisoners in solitary confinement,
A, B and C, have been sentenced to death on the same day but, because
there is a national holiday, the governor decides that one will be
granted a pardon. The p... | 69,390 |
<p>I am doing a PCA on a few economic indices (which I standardized) (24 timeseries). When doing the PCA on the values/level of the index, I get rather similar loadings on each index, which I think is good, as no one should dominate. However when I run it on the returns of these standardized indices, the loadings are m... | 69,391 |
<p>I'm running a GEE on 3-level unbalanced data, using a logit link. How does this differ (in terms of the conclusions I can draw and the meaning of the coefficients) from a GLM with mixed effects (GLMM) and logit link?</p>
<p>More detail: The observations are single bernoulli trials. They are grouped clustered into ... | 69,392 |
<p>I have two questions about confidence intervals:</p>
<p>Apparently a narrow confidence interval implies that there is a smaller chance of obtaining an observation within that interval, therefore, our accuracy is higher.</p>
<p>Also a 95% confidence interval is narrower than a 99% confidence interval which is wider... | 69,393 |
<p>We have a set of XY coordinates which we have fitted with an orthogonal least square regression model. We have a vector of residuals for each point and the fitted line. How do we assess goodness of fit quantitatively? We're currently using Matlab but are open to other approaches. </p> | 69,394 |
<p>We are trying to predict values of variable A having N other variables. What we do, we calculate Pearson correlation between A and each of the other N variables, for last M values, using fixed M. We use variable with largest correlation coefficient as predictor.</p>
<p>This scheme works fine when analyzing N variab... | 40,065 |
<p>Let's take the following example:</p>
<pre><code>set.seed(342)
x1 <- runif(100)
x2 <- runif(100)
y <- x1+x2 + 2*x1*x2 + rnorm(100)
fit <- lm(y~x1*x2)
</code></pre>
<p>This creates a model of y based on x1 and x2, using a OLS regression. If we wish to predict y for a given x_vec we could simply use the... | 49,410 |
<p>I am currently working on a project where I generate random values using <a href="http://www.puc-rio.br/marco.ind/quasi_mc.html" rel="nofollow">low discrepancy / quasi-random point sets</a>, such as Halton and Sobol point sets. These are essentially $d$-dimensional vectors that mimic a $d$-dimensional uniform(0,1) v... | 69,395 |
<p>Say there are 3 companies A, B and C. Each company has a quality rating from 0 to 100 and a price in USD.</p>
<pre><code>Company Quality Price
A 80 7.9
B 70 8.0
C 75 8.1
</code></pre>
<p>How do I determine the best quality-price trade-off? What kind of analy... | 49,298 |
<p>I am a CS graduate student and I am starting to get really interested in Machine Learning (and Predictive Analytics). I have started working on a text classification project with a professor to learn the field but I am realizing that my background is pretty weak. The professor is too busy to teach me the basics, so ... | 69,396 |
<p>Given two point sets, $B$ consisting of blue points, and $R$ of red points, on the plane.</p>
<p>The problem is to formulate a theoretical model to compare the average runtime of the Computational Geometric (CG) Algorithm and the <a href="http://en.wikipedia.org/wiki/Perceptron#Learning_algorithm" rel="nofollow"> P... | 69,397 |
<p>How can one obtain confidence limits of predicted values in ARIMA?</p> | 69,398 |
<p>In PCA eigenvalues determine the order of components. In ICA I am using kurtosis to obtain the ordering. What are some accepted methods to assess the number, (given I have the order) of components that are singificant apart from prior knowledge about the signal?</p> | 69,399 |
<p>Satellite-Routed sensor system has attracted attention in next generation network. In this system large number of sensor terminals send sensed data to the monitoring station located in different area via a satellite. The problem of this system that large number of sensor terminals trying to transmit their sensed dat... | 69,400 |
<p>I'm measuring distances of various samples from a reference point. The distance is defined as a non-negative number, where $d=0$ means that the test case is identical to the reference. </p>
<p>My general question is: Given a set of "typical" distances, what is the proper way to tell whether a given $d_1$ "too larg... | 69,401 |
<p>I'm trying to design an experiment where I measure a variable as a function of 5 two-level factors, labelled A, B, C, D and E.</p>
<p>I'm trying to understand how to best design this experiment so I can conduct it in 8 runs. I've tried to follow the guidance given in Box, Hunter & Hunter, and found two experime... | 40,072 |
<p>I was working on ARIMA in R and I am trying not to use library <code>forecast</code> as much as possible. I have a code for finding the best ARIMA model, but it is showing some warning messages.</p>
<p>Here is my function:</p>
<pre><code>best.aic<-1e8
n<-length(x.ts)
for(p in 0:maxord[1]) for(d in 0:maxord[2... | 69,402 |
<p>I have an independent variable “State in the US” and it has around 16 different levels (PA, NY, NJ, etc). Now I have combined the states which appear infrequently into "others" category. But I still have around 12 levels which are equally populated. </p>
<p>I have a very large data set (1 million observations) and ... | 69,403 |
<p>I'm having trouble writing the likelihood for a homework question:</p>
<p>Suppose $X=Z(Y+\theta)+(1-Z)(\theta-Y)$ and $X_1, X_2, X_3 \overset{iid}{\sim} f_X(x)$ where $Z\sim \rm{Bernoulli}(0.5)$ and $Y\sim \rm{exponential}(1)$ and $Z$ and $Y$ are independent. Let $x=(7.2, 9.3, 8.6)$ be the observed data. </p>
<p>C... | 69,404 |
<p><strong>Background:</strong> We work with data from sports event, more accurately with data about the spectators of sports events: how many people are being violent, what kind of event is this, etc. We have quite a lot of data from the past few years and we try to find the "right" number of security people we need t... | 69,405 |
<p>I just watched a lecture on statistical inference ("comparing proportions and means"), part of an intro to stats online course. The material made as little sense to me as it always does (by now I must have seen this stuff dozens of times, spread out over the last three decades).</p>
<blockquote>
<p>I'm looking f... | 69,406 |
<p>The goal of both methods seems to be to derive an estimate of a posterior/target distribution. If a process model exists which links some input parameters (which are themselves uncertain and can be described by a PDF) to an output parameter through a model equation or other computations, why would one choose one met... | 98 |
<p>I'm looking for an algorithm which can optimize the selection of queries used to build a decision tree. However, unlike most decision trees, I am constrained to ask the same set of questions for every case.</p>
<p>I'll couch this in the form of the parlor game <a href="https://en.wikipedia.org/wiki/Twenty_Question... | 69,407 |
<p>I want to introduce observations errors around my data in Jags, but I face some trouble coding it without having a double definition error on node Y3</p>
<p>So far I have :</p>
<pre><code>log_Y1_real[y]~dnorm(log(Y1[y]),prec_obs_Y1) #Y1 is one variable
log_Y2_real[y]~dnorm(log(Y2[y]),prec_obs_Y2) #Y2 is an... | 877 |
<p>This seems to be a basic issue, but I just realized that I actually don't know how to test equality of coefficients from two different regressions. Can anyone shed some light on this? </p>
<p>More formally, suppose I ran the following two regressions: $y_1 = X_1\beta_1 + \epsilon_1$ and $y_2 = X_2\beta_2 + \epsilon... | 49,346 |
<p>I'm using Stanford CoreNLP's dependency parser, and wondering how to make a generic search for SemanticEdge(s) with specific head lemma, dependent lemma, and lexical relationship. For example, if I have an actual dependency like this:</p>
<ul>
<li>dobj(discover-4, insights-6)</li>
</ul>
<p>How do I search for it u... | 21,538 |
<p>Suppose I have stationary time series data, like this: </p>
<p><img src="http://i.stack.imgur.com/N7Oua.png" alt="enter image description here"></p>
<p>The time series has Gaussian noise around a true mean. If I then take windows of N samples across the series and average them to generate a new serie, How are the ... | 69,408 |
<p>I read the article "Two-way imputation: A Bayesian method for estimating missing
scores in tests and questionnaires, and an accurate approximation" by Van Ginkel et al. (available <a href="http://members.home.nl/jeroenvermunt/ginkel2006.pdf" rel="nofollow">here</a>) about a Bayesian two-way imputation method for est... | 29,867 |
<p>Suppose I have a homogeneous time series $x_n$, where the values arrive each second. For $n\ge 60$, let $\sigma_n$ be the standard deviation of the values $x_{n-59},\ldots,x_n$.</p>
<p>Under the assumption that $x_{n+60}\sim\sigma_n\mathcal{T}(\nu)+\varepsilon_n$, where $\mathcal{T}(\nu)$ is the student's $t$-distr... | 69,409 |
<p>I'm displaying time-series data as a "stacked line" or "stacked area" chart. (E.g. with percentage data, data points at 10%, 20% and 30% are displayed at 10%, 30% and 60% on the chart.) Unsmoothed lines through the data points obviously never cross (and never go below the minimum data value or above the maximum tota... | 69,410 |
<p>I have two questions about the notion of block in experimental design :
(1) What is the difference between a block and a factor ?
(2) I tried to read some books but something is not clear: it seems that the authors always assume that there is no interaction between the "block factor' and other factors. Is it right, ... | 29,868 |
<p>Empirically the quartimax-/varimax-rotation has proven useful and it was always converging in my applications. But from my readings years ago I have a vague remembering, that the fact of a proof of convergence has been mentioned but I've never seen the actual proof. </p>
<p>Perhaps this is not difficult and m... | 40,084 |
<p>I have built what I think is a very good predictive model using randomforest. The initial dataset was imbalanced for the outcome 2:1, so I randomly resampled the dataset to balance it, then trimmed the predictors down to 20 or so and managed to get the sensitivity and specificity of the model up to the 90s based on ... | 29,870 |
<p>I'm doing a Logistic Regression on company level using the total assets to control for company size. Due to the skewedness of the data, I do a log-transformation of the asset data. While I get no significance for the log-transformed variable, the not transformed variable is highly significant (p < 0.01). What cou... | 49,358 |
<p>My friend and I are discussing about the convergence of Variational Inference, especial for Expectation Propagation method. After running some loops, the likelihood of my graphical model can be plotted like the below figure (the x axis is the number of iteration and the y axis is the likelihood value). When the like... | 28,416 |
<p>Can anybody help me out with the following question?</p>
<p>The distribution of the age at which all married males got married is right skewed with mean = 22.9 years and standard deviation = 1.5 years. What is the probability that an SRS of 75 married males would have a sample mean between 22.8 and 23.0?</p> | 69,411 |
<p>I currently look for a set of ngrams in many sets of documents to establish a relevancy score for each set - <em>eg. I look for the n-gram "adhesive tape" in ~1M sets of 1-500 documents.</em></p>
<p>The values I have at my disposal are:</p>
<ul>
<li>the total documents in each set</li>
<li>the total documents each... | 69,412 |
<p>I have some data X where the samples are not independent (they're correlated with each other), and I'm trying to do a regression of some continuous variable y on X. This sample correlation could confound my analysis.</p>
<p>Hence, I thought of using ZCA whitening to correct for this inter-sample covariance in X
$$
... | 69,413 |
<p><strong>Update</strong>: Since I now know that my problem is called <strong>quasi-complete separation</strong> I updated the question to reflect this (thanks to Aaron).</p>
<hr>
<p>I have a dataset from an experiment in which 29 human participants (factor <code>code</code>) worked on a set of trials and the <code>... | 69,414 |
<p>I am trying to reproduce a paper on two stage randomized clinical trials. In these clinical trials, a patient is randomized to either of the maintenance therapies $B_1$ or $B_2$ upon their remission after getting the induction therapy $A_1$. The remission probability is taken to be 0.80 and the 2nd stage randomizati... | 69,415 |
<p>I have in my model two dummy's, for a categorical variable with 3 categories (native, EU-immigrant and non-EU-immigrant). The reference category is 'native'. These are merely control variables. </p>
<p>Now I find a significant coefficient for one dummy, and not for the other. See last 2 rows here. Note these are lo... | 69,416 |
<p>I was unable to understand how to compare multiple mean values in each group. Within the subgroup the mean values influence each other (If one changes, the other changes automatically). </p>
<p>I collected travel distance and the mode of transportation choice at two different locations. There are 32 people in each ... | 69,417 |
<p>I wanted to find a variant of the perceptron which works for non-separable data, so I tried using $f(x)=\mathrm{\tanh}(x)$ instead of the hard threshold function and finding a $w$ that minimises the function $$\frac{1}{2} \sum_i (y_i - f(w \cdot x_i))^2$$
where $y_i \in \{-1,1\}$ are the classes of the training exam... | 69,418 |
<p>I'm trying to calculate the mean survival time of a Weibull distribution, and am getting what feels like an errant estimate of the mean--and each source I look up for how to calculate the mean gives a slightly different formulation.</p>
<p>Going from Klein and Moeschberger, the mean is:</p>
<p>$$\frac{\Gamma(1+1/\... | 69,419 |
<p>I am trying to figure out how to simulate bootstrap samples from a dataset with unbalanced clusters. The approach I would like to adopt is <strong>non-parametric pairs bootstrap</strong>, which easily allows to maintain the dependence structure of the clusters. </p>
<p>Suppose for a moment that data were balanced (... | 40,097 |
<p>I have recently begun to read about bayesian statistics and I am playing around with the R2WinBUGS package. I'm trying to fit a logistic regression to the spam data (that can be found on the webpage of the elements of statistical learning) using R and WinBUGS. My approach was to first divide the data into 80% traini... | 69,420 |
<h2>The Real World Problem</h2>
<p>One of my clients is preparing to send a direct mailer to their subscribed user list, and this statistical challenge came up.</p>
<p>Their marketing team has 3 different brochures, and wants to know which brochure gets the highest response rate. They would also like to know if send... | 40,099 |
<p><strong>Is it possible to control the cost of misclassification in the R package <a href="http://cran.r-project.org/web/packages/randomForest/index.html">randomForest</a>?</strong> </p>
<p>In my own work false negatives (e.g., missing in error that a person may have a disease) are far more costly than false positiv... | 37,441 |
<p>A simulation gives the population numbers for every species in the domain per frame. These vary over time and can be quite noisy, for example we might have:</p>
<p>Species A: <code>1, 1, 2, 3, 4, 5, 5, 4, 3, 2, 1</code></p>
<p>Species B: <code>5, 4, 3, 3, 2, 2, 2, 1, 2, 3, 4</code></p>
<p>Fourier analysis gives:<... | 29,876 |
<p>I am faced with a problem, that I'm pretty sure is a statistical one, but me taking 1 course in probability followed by 1 course in statistics back in university did not prepare me to adequately face it. With that in mind, while a R-based sample code is always helpful and appreciated, what I'm really after is some d... | 40,102 |
<p>In some lecture notes I am reading, there is the following;</p>
<p>Consider $X_{1},...,X_{n}$, each with pdf $g$ (the instrumental distribution). Our aim is to estimate $E_{f}[h(X)]$ where $h(X)$ is some measurable function and $f$ a pdf (the target distribution).</p>
<p>Then:</p>
<p>$\large\frac{1}{n}\displaysty... | 45,409 |
<p>I KNOW what moments are and how to calculate them and how to use the moment generating function for getting higher order moments. Yes, I know the math.</p>
<p>Now that I need to get my statistics knowledge lubricated for work, I thought I might as well ask this question - it's been nagging me for about a few years ... | 69,421 |
<p>Say I have the following obvious Bayesian computation:</p>
<p><img src="http://i.stack.imgur.com/1Bjsx.png" alt="enter image description here"></p>
<p>where $\theta$ is a model parameter that we try to infer and $D$ is <strong>observed data</strong>.</p>
<p>I have always understood $p(D)$ to relate to knowledge t... | 69,422 |
<p>I couldn't find the scripts for Mixed-Effects Models in S and S-PLUS. The only place is <a href="http://stat.bell-labs.com/project/nlme/MEMSS/index.html#OnLine" rel="nofollow">http://stat.bell-labs.com</a> which has code for first two chapters. I'd highly appreciate if someone point out the place to get the scripts ... | 29,879 |
<p>I recently read the advice that you should generally use median not mean to eliminate outliers.
Example:
The following article
<a href="http://rads.stackoverflow.com/amzn/click/1420064932">http://www.amazon.com/Forensic-Science-Introduction-Scientific-Investigative/product-reviews/1420064932/</a></p>
<p>has 16 revi... | 69,423 |
<p>In a repeated measured design we measure a particular variable at different time points from the same subjects. In animal experiments, if animals are sacrificed at every time point to measure a variable, theoretically the measurements at every time point are from different animals, though the measured variable is sa... | 69,424 |
<p>The <a href="http://en.wikipedia.org/wiki/Copula_%28probability_theory%29#Fr.C3.A9chet.E2.80.93Hoeffding_copula_bounds" rel="nofollow">Fréchet–Hoeffding upper bound</a> applies to the copula distribution function and it is given by</p>
<p>$$C(u_1,...,u_d)\leq \min\{u_1,..,u_d\}.$$</p>
<p>Is there a similar (in the... | 69,425 |
<p>I'm teaching myself to translate equations to code after many years of letting my math skills atrophy, and am trying to do it on my own as much as possible. I've run into a couple of difficult equations though that I just can't solve without a few pointers though, particularly the one for Mahalanobis distances menti... | 69,426 |
<p>If you have performed a statistical test using the standard 95% confidence threshold then a p-value of < 0.05 will indicate significance. </p>
<p>I was reading <a href="http://myowelt.blogspot.co.uk/2008/04/beautiful-correlation-tables-in-r.html" rel="nofollow">a blog post</a> about typesetting some correlation ... | 29,883 |
<p>I'm running a lmer mixed effects model with a four-level factor (levels "0","10","100","1000") as the fixed effect.</p>
<pre><code>lmer(free ~ reward.f + (1|S), longdata)
</code></pre>
<p>I know that by default, R uses treatment contrasts and the levels 10, 100, and 1000 are compared to level "0". I would instead ... | 29,884 |
<p>Given a list of $k$ non-negative integers $m_i$, $i=1,...,k$, and a positive integer $n$, with $n\ge m +k$, where $m=\sum m_i$. I need to generate $k$ random positive integers $n_i$, such that $\sum n_i = n$, $n_i > m_i$, and $n_i=1$ whenever $m_i=0$.</p>
<p>What's the simplest way of accomplishing this using an... | 69,427 |
<p>Based on readings with logistic regression, it appears that you could use this analysis to make predictions about categorical variables. Does logistic regression allow you to predict multiple dependent variables with one independent variable, or just one? For example, if I were looking at predicting the gender of so... | 69,428 |
<p>I am using <code>seqecreate</code> to specify an event sequence object using <code>TraMineR</code>. </p>
<p>The dataset has 1271 rows and 4 columns, an id, timestamp (timed), and 2 event variables (one numeric and one string). Most of the data have only 1 event per id. I've done other analyses with these data in... | 39,275 |
<p>Carlin (2005) points out that mixed effects models specifically for twin data can be simplified by calculating differences between paired clusters. This allows for modeling specifically the within cluster effects and cancelling out any between cluster effects.</p>
<p><a href="http://ije.oxfordjournals.org/content/3... | 48,918 |
<p>I have more than five hundred thousands samples of a continuous variable measured in two groups: a treatment and a control one.
I would like to decide whether the measurements follow the same (unknown) distribution in the two groups.</p>
<p>Graphically this seems to be the case: the density functions (obtained usin... | 69,429 |
<p>Interpretation of t-test value (2 tailed): ~20% chance that these results could have been obtained randomly.</p>
<p>My intuition: MEAN_2 - MEAN_1 = ~3% of MIN(STD_1, STD2). Calculate area under normal normal PDF between -3% and +3% of std from mean which is ~2.5%. </p>
<p>Why is the t-test result so far off from m... | 69,430 |
<p>The MATLAB code at <a href="http://read.pudn.com/downloads106/sourcecode/graph/texture_mapping/436817/matlab/utvisToolbox/tutorials/SIFTtutorial/fit_robust_affine_transform.m__.htm" rel="nofollow">this</a> link can be used to estimate the affine transform between two sets of 2D points. The code makes the implicit as... | 69,431 |
<p>I have the following estimations of a fixed effects model:</p>
<p>Open=β0+ β1Pol_r+ β2Infr+ β3Nat_re+ δ4SACU+ɤi+εit</p>
<p>Open_ln=β0+ β1Pol_r+ β2Infr+ β3Nat_re+ δ4SACU+ɤi+εit</p>
<p>Where Open is the openness of a country measured as ((imports+exports)/GDP)*100, Open_ln is the natural logarithm of Open. SACU is ... | 49,290 |
<p>Suppose I have an experiment that has 8 factors. These 8 factors are probably related and can hopefully be reduced. For each combination of these 8 factors that I test, I get a single output. My goal is to reduce the 8 factors to a smaller set of variables. In this case is PCA or Factor Analysis more appropriate?</p... | 29,890 |
<p>What is the best way to model coin flips as a hierarchical model? Do you say coin draws are a series of draws from Bernoulli trials or as one draw from a binomial distribution?</p>
<p>That is something like this:</p>
<pre><code>model {
p ~ dunif( 0, 1 )
for( i in 1 : n) {
h[i] ~ dbern( p )
}
}
</code></p... | 69,432 |
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