question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>Are there any generic tests to validate if a given sample follows a unimodal distribution, like a Gaussian, Cauchy, Student's t or a chi-square?</p> | 33,751 |
<p>In R, the function <code>wilcox.test</code> takes the argument <code>conf.level = 0.095</code> (for example). Giving the same argument to the function <code>wilcoxsign_test</code> from the <em>coin</em> package returns a warning:</p>
<pre><code>additional arguments conf.level will be ignored
</code></pre>
<p><stro... | 71,993 |
<p>Is <a href="http://stats.stackexchange.com/questions/10744/how-does-quantile-normalization-work">quantile normalization</a> adequate for normalizing
data with very few samples?</p>
<p>For example this microarray data. Typically after normalization
we'd like to compare <code>Cancer-1 with Normal</code> and <code>Ca... | 71,994 |
<p>Background: My organization currently compares its workforce diversity statistics (ex. % persons with disabilities, % women, % veterans) to the total labor force availability for those groups based on the American Community Survey (a surveying project by the US Census Bureau). This is an inaccurate benchmark, becau... | 71,995 |
<p>Cost per click is defined by the cost per impression and the click through rate. Given a period of time, divide number of clicks by the sum of the cost per impression for all ads in the same time period.</p>
<p>Cost per click is equivalent to click through rate multiplied by cost per impression (which are assumed t... | 71,996 |
<p>The high dimensional variable selection problem is really popular now. But I have a question: If I do simple linear regression regressing one response variable on 1 covariate at a time first and then control the FDR to select the significant feature variables, what's the disadvantage of this comparing to the lasso o... | 44,731 |
<p>I am trying to get my head around the best way to analyse a study.</p>
<p>The study comprises of persons that get given a number of up to 10 different interventions, whereby hospital admission frequency is measured as an outcome.</p>
<p>Each intervention are not given out randomly, and some persons are not require... | 12,441 |
<p>I did perform a search for this question (I thought it was bound to be asked), but I haven't found one; hopefully this won't be a duplicate.</p>
<p>I'm trying to decide if I should take a course in stats that is more parametric or one that is nonparametric. </p>
<p>From a maths perspective, what would be the advan... | 33,756 |
<p>I have a dataset of $n$ $p$-dimensional vectors (objects) that I want to cluster.</p>
<ol>
<li><p>One way to do this is to compute the ($n \times n$) correlation matrix $C$, then obtain a dissimilarity matrix, $D$, from $C$ such that each element $d_{ij}$ in $D$ is a function of the single element $c_{ij}$ in $C$ (... | 71,997 |
<p>I have a directed graph, <strong>S</strong>, where each vertex stores several integers of attributes. I think it might be called a <a href="http://stackoverflow.com/questions/2688389/what-are-attribute-relational-graphs">"attribute relational graph"</a> or just an old fashioned "attributed graph". The networkx Pytho... | 44,733 |
<p>Quick question about sampling a data population that contains non-overlapping data: if I take two samples of 50 from a population of 100,000 unique data points, how would I calculate the probability of the two samples containing a shared data point?</p>
<p>As well, how do I determine the population size required fo... | 71,998 |
<p>What methods of analysis are utilized for pre/post test data when outcome are knowledge scores? In addition what methods of analysis would be used for Likert behavioral score data?</p> | 49,500 |
<p><img src="http://i.stack.imgur.com/ujlEW.png" alt="Question"></p>
<p>I have done part(a); now I need to do part(b): I want to simulate the distribution of the median $M$ using R. I don't know how to work it out. </p>
<p>And for part(c), do I need to use R as well?</p>
<p>This is what I have done</p>
<pre><code>m... | 33,759 |
<p>Is there a variation of Latent Dirichlet Allocation (LDA) for grouped data? As an example, let us consider corpus of all Yahoo Q&A (where for simplicity we consider a question lumped together with all the corresponding answers as a document). While submitting a question to Yahoo's site, user has to specify a cat... | 71,999 |
<p>I was reading on Gelman's Bayesian Data Analysis - Chapter 5 - Hierarchical model</p>
<p>Suppose:
data : $y_j$ s</p>
<p>parameter: $\theta$</p>
<p>hyperparameter: $\phi$</p>
<p>On page 126, he mentions the analytical derivation of conditional and marginal distributions. </p>
<p>I understand that we can easily d... | 33,760 |
<p>Suppose we are given data $y_j \sim \text{Poi}(\lambda)$ and assume $y_j$ are iid.
We can assume the prior distribution for $\theta$ follows $\text{Gamma}(\alpha, \beta)$, </p>
<p>The posterior distribution of $\theta | y$ is also Gamma while the posterior predictive distribution is Negative Binomial. </p>
<p>My ... | 33,761 |
<p>I have a lot of address strings:</p>
<pre><code>1600 Pennsylvania Ave, Washington, DC 20500 USA
</code></pre>
<p>I want to parse them into their components:</p>
<pre><code>street: 1600 Pennsylvania Ave
city: Washington
province: DC
postcode: 20500
country: USA
</code></pre>
<p>But of course the data is dirty: it... | 44,735 |
<p>So, this question is somewhat involved but I have painstakingly tried to make it as straight-forward as possible. </p>
<p><strong>Goal:</strong> Long story short, there is a derivation of negentropy that does <em>not</em> involve higher order cummulants, and I am trying to understand how it was derived. </p>
<p>... | 72,000 |
<p>I have data on 18 participants responding to a 30-item instrument.
I also have a paper in which the researchers performed a principal axis factor analysis on the same survey where they report the item loadings (4 factors). </p>
<p><strong>Is it possible to convert the data that I have, and compute scores for each ... | 72,001 |
<p>Imagine a population of people where $x\%$ have blue hats and $(100-x)\%$ have green hats where every year some people are awarded prizes. The rule is that everyone should have an equal chance of being awarded a prize every year. The village bosses would like to decide if this rule is being followed as they suspec... | 72,002 |
<p>As a financial institution, we often run into analysis of time series data. A lot of times we end up doing regression using time series variables. As this happens, we often encounter residuals with time series structure that violates basic assumption of independent errors in OLS regression. Recently we are building... | 15,052 |
<p>I have this confusion related to how this density was estimate. I have attached the screenshot of the paper</p>
<p>Any references related to basis expansion and all. I didn't get how this was derived actually.</p>
<p><img src="http://i.stack.imgur.com/R5Xxu.png" alt="enter image description here"></p> | 72,003 |
<p>The following code evaluates the similarity between two time series:</p>
<pre><code>set.seed(10)
RandData <- rnorm(8760*2)
America <- rep(c('NewYork','Miami'),each=8760)
Date = seq(from=as.POSIXct("1991-01-01 00:00"),
to=as.POSIXct("1991-12-31 23:00"), length=8760)
DatNew <- data.frame(Loc = ... | 47,810 |
<p>I was reading a paper related to minimaxity.</p>
<p><img src="http://i.stack.imgur.com/5tTGZ.png" alt="enter image description here"></p>
<p>If $\hat{\theta}$ is the estimate of an unknown parameter $\theta$ and $l(\hat\theta-\theta)$ is the loss function they have mentioned $E_p$ is the mean of $l(\hat\theta-\the... | 72,004 |
<p>I have the following data (relating to consecutive months at current job):</p>
<ul>
<li>Mean: 45.4</li>
<li>Standard Deviation: 60.89</li>
<li>Sample Size: 48</li>
</ul>
<p>I am asked to do a one-tailed test at a 1% significance level and provide:</p>
<ol>
<li>the value of the test statistic (from above).</li>
<l... | 33,769 |
<p>$$My \ \ dataset:$$
$$1: A,B,C,E$$
$$2:A,C,D,E$$
$$3:\ \ \ \ \ B,C,E$$
$$4:A,C,D,E$$
$$5:\ \ \ \ C, D, E$$
$$6: \ \ \ \ A, D,E$$</p>
<p>I want to find out the <strong>maximal frequent item sets</strong> and the <strong>closed frequent item sets</strong>.</p>
<ul>
<li>Frequent item set $X ∈ F$ is <strong>maximal<... | 803 |
<p>I have lots of football result data, and I want to test the dependency of the number of goals per game on the weather (e.g. sun, rain, snow). I'm struggling to decide if the data is dependent or independent (and hence which ANOVA test to use). I can't be sure that every team will have played every other team more th... | 72,005 |
<p>My research hypothesis is that an intervention, I, results in greater scores than the control,C. If the intervals for these two don't overlap, I know I can make a clear-cut statement either accepting or rejecting my hypothesis. However, I also want to make "degree of evidence in favor of" types of statements shoul... | 72,006 |
<p>I want to run nine different ANOVAs on different variables that may change among groups. The ANOVAs are preceded by the Levene test of variance homogeneity. Of course, I want to correct for multiple comparisons in the final alpha threshold for the ANOVAs.</p>
<p>But as random p values can be under 0.05 in all tests... | 33,775 |
<p>I'm sorry in advance for rather long questions. This is an example in "Bayesian logical data analysis for physical sciences" by P. C. Gregory and I have some questions about the example.</p>
<blockquote>
<p>In a poll of 800 decided voters, 440 voters supported the political party A. Let's denote the poll result a... | 37,658 |
<p>For a paper I'm using Fisher's Exact Test in R. As I already found out the p.value in R is calculated as the sum of all probabilities of the hypergeometric distribution with the given parameters lower or equal the the probability of the observed value.
And I already learned that there are multiple ways of calculatin... | 44,432 |
<p>I recently completed a study whereby I randomly assigned participants to one of two treatment groups. I tested participants at baseline, immediately post-intervention, 1 months, and 4 months on a somewhat large number of outcome variables. I was planning on running several mixed ANOVAs to examine group x time inter... | 72,007 |
<p>I am currently training a random forest regressor (scikit learn) on the Titanic dataset. </p>
<p>My question is related to this issue (<a href="http://stackoverflow.com/questions/19984957/scikit-predict-default-threshold">http://stackoverflow.com/questions/19984957/scikit-predict-default-threshold</a>) on stack ove... | 72,008 |
<p>I'm using nlme in R to fit a multilevel model for some physiological (skin conductance level) responses while watching a film. I'm specifying the model as:</p>
<p>model <- lme(SCL <- variableA * variableB + TIME, random=~TIME|SUBJECTS, data=data5, na.action=na.omit, control=list(opt="optim"), method="ML", cor... | 72,009 |
<p>I'm working on an algorithm which needs to calculate the size of a set generated by the intersections of at least 2 sets. More specifically:</p>
<p>$$
z = \left |A_0 \cap \ldots \cap A_n \right |
$$</p>
<p>The sets that are intersected are generated by SQL queries, and in an effort to keep things fast, I get a cou... | 72,010 |
<p>I have data that looks a bit like this </p>
<pre><code> A<-c(90,95,70,45,20,15)
B<-c(10,5,30,55,80,85)
X<-c("X1","X2","X1","X2","X1","X2")
Z<-c("Z1","Z1","Z2","Z2","Z3","Z3")
</code></pre>
<p>I've carried out a glm </p>
<pre><code> mod1<-glm(cbind(A,B)~X*Z, binomial)
Coefficients:
... | 72,011 |
<p>I do have some 10-12 independent variable, I want to know how these 10-12 variables are related to a single variable(X). so I can decide that some variables are positively correlated to X and some are negatively correlated. I thought of doing correlation between X and one of the independent variables individually an... | 72,012 |
<p>Can any one help me?</p>
<p>I develop a scale with 31 items, and I expect to have five (5) factors in EFA but after conducting EFA, nine (9) factors were extracted. I want to know what cause this situation and how to solve the problem to have my 5 factors in my original model. Thank you.</p> | 30,729 |
<p>(First of all, just to confirm, an offset variable functions basically the same way in Poisson and negative binomial regression, right?)</p>
<p>Reading about the use of an offset variable, it seems to me that most sources recommend including that variable as an option in statistical packages (exp() in Stata or offs... | 72,013 |
<p>I am trying to code a visualization with 4 variables ( Carbon emission, Energy consumption, population and year)</p>
<p>The data set i have collected so far looks like this </p>
<p>With C1990 representing Carbon emission data 1990 and so on.
<img src="http://i.stack.imgur.com/oMtR4.jpg" alt="enter image descripti... | 72,014 |
<p>I want to find $\theta$ such that</p>
<p>$ \theta = argmin_{\theta} \left( \left|\left| Y - \sum_{i=1}^k \theta_i X_i \right|\right| \right) $
</p>
<p>where $X_i$ and $Y$ are N x N matrices and $\theta$ is a weight vector that specifies how to linearly combine the $k$ $X$'s to approximate Y.</p>
<p>This smells li... | 72,015 |
<p>I had a quick question. I am trying to test the correlation between the % coral cover at each of my study sites, and the % of coral in sediment collected from those sites. The problem is that the coral cover per site is obtained independently of how the % coral in sediment is obtained. Specifically, I have a valu... | 72,016 |
<p>I have data points from a half circle and I already know the radius. I want to find the circle which best fits the points using a fixed radius. How can I do this? If I solve the problem using a typical circle fit algorithm the radius is too unstable due to "noise".</p> | 33,791 |
<p>I am running a series of regressions to eliminate the effects of IQ, language ability and age from my variables (task performance). To do this, the variable is entered as the dependent variable (e.g. EFT in syntax below) in a regression with IQ, language ability and age as predictor variables, selecting for control ... | 875 |
<p>My feature data is defined in such a way that I believe all weights must be non-negative.
I am looking for a reference discussing how to optimize the weights of a logistic regression classifier with the constraint that the weights must be non-negative, and perhaps also a constraint on the sign of the bias.</p>
<p>W... | 72,017 |
<p>I have worked on clinical trials in FDA submissions for many years. I use SAS almost exclusively. Recently I discussed a consulting job I had to bootstrap a Deming regression. Bootstrapping is much more easily done in R I think and several experts have suggested ways that I can do this in R. Since this is going into... | 44,783 |
<p>I have computed the mean and standard deviation of a variable in a dataset, and I wish to represent these values in a report. Is the following the correct way to go about this?</p>
<p>$1.23 \pm 0.52 \sigma$,</p>
<p>where the mean is 1.23 and the standard deviation is 0.52.</p>
<p>Alternatively, would a standard e... | 44,786 |
<p>Could anybody provide me a latest material related to Cross validation especially R package?</p> | 44,788 |
<p>I have 3 to 5 measures of a trait per individual in two different conditions (A and B).</p>
<p>I'm plotting the average for each individual in each condition and I use the standard error (<em>i.e.</em>, $SD/\sqrt{N}$, with $N$ = number of measurements) as error bars.</p>
<p>Now I want to plot the difference betwee... | 33,793 |
<p>My question is about model selection/comparison in the case of discrete outcome spaces <em>and</em> when the number of distinct outcomes depends on the dimension. (For the curious minded, this arises naturally, and is in fact the definition of dimension, in quantum mechanical models.) </p>
<p>I'll give a simple an... | 72,018 |
<p>We have the following update formulas:</p>
<p>Output layer (indexed by $k \in \{1, \dots, \text{number of classes} \}$).</p>
<p>$o_k$ - value of output neuron $k$</p>
<p>$d_k$ - desired value of output neuron $k$</p>
<p>$\eta$ - learning rate</p>
<p>$x_j$ - value of neuron on the last hidden layer </p>
<p>$$\d... | 72,019 |
<p>I have a dendrogram called <code>x</code> and I want to reorder it. First, I make sure that <code>x</code> is a dendrogram, and it is:</p>
<pre><code>> class(x)
[1] "dendrogram"
</code></pre>
<p>Then I check the order of things in my dendrogram, and it's exactly as it is drawn, i.e. everything makes sense:</p>... | 33,796 |
<p>In our usage of R for a non-trivial data analysis and estimation project, we've been repeatedly burnt by how tolerant R is toward misspelled or missing columns in a data frame. Typical example is calculating the weighted mean of a variable MYVAR in a data frame using another variable WEIGHT for weights:</p>
<pre><c... | 72,020 |
<p>We need to estimate the probability of a person getting a question right for a given content area given his history of getting questions in the same content area right in the past. We would also presumably have records on how others have done on this question and in this content area.</p>
<p>Is there a good way or... | 72,021 |
<p>Breiman says that the trees are grown with out pruning. Why? I mean to say that there must be a solid reason why the trees in random forest are not pruned. On the other hand it is considered very important to prune a single decision tree to avoid over fitting. Is there some literature available to read for this reas... | 33,797 |
<p>I am dealing with handling overdispersed count data(Poisson distributions fails to fit).</p>
<p>I need to compare three different mixtures (Gamma, Log-Normal and Inverse Gaussian) of Poisson rate parameter distributions using a simulation study. </p>
<p>I would like to know the available methods(apart from Likelih... | 72,022 |
<p>I would like to determine whether there is a deviation in the male:female ratio of a certain strain of laboratory mouse from the normal situation (with male:female = 1:1).</p>
<p>I have several mouse pairs, and several litters for each pair.</p>
<p>So, for instance:</p>
<pre><code>Pair 1
Litter 1 5M:3F
Lit... | 72,023 |
<p>Let:</p>
<p>Standard deviation of random variable $A =\sigma_{1}=5$
</p>
<p>Standard deviation of random variable $B=\sigma_{2}=4$
</p>
<p>Then the variance of A+B is:</p>
<p>$Var(w_{1}A+w_{2}B)= w_{1}^{2}\sigma_{1}^{2}+w_{2}^{2}\sigma_{2}^{2} +2w_{1}w_{2}p_{1,2}\sigma_{1}\sigma_{2}$
</p>
<p>Where:</p>
<p>$p_{... | 72,024 |
<ol>
<li><p>Does anyone know how to create a nice looking summary table in JMP for several variables? I use Tables>Summary and the table I get has one row that includes for example mean(var1) mean(var2) mean(var3) median(var1) median(var2) median(var3) and so on. I would like each variable to have row of its own, with ... | 72,025 |
<p>Say we have two Gaussian random vectors $p(x_1) = N(0,\Sigma_1), p(x_2) = N(0,\Sigma_2)$, is there a well known result for the expectation of their product $E[x_1x_2^T]$ without assuming independence?</p> | 44,805 |
<p>From a given sample $x_i \underset{\mathrm{iid}}{\sim} {\cal N}(\mu, \sigma^2)$ it is possible to get a confidence interval about the probability $\Pr(x_i \geq a)$ for any number $a$, by "inverting" some tolerance intervals. </p>
<p>If ${\boldsymbol x}_i \underset{\mathrm{iid}}{\sim}{\cal N}_p({\boldsymbol \mu}, \S... | 72,026 |
<p>I would like to estimate the variance of the error term in the ordinary linear regression model. The obvious estimate is the sample variance of the residuals, however this estimate consistently underestimates the real value. A simple simulation in R confirms that:</p>
<pre><code> x = rep(0:1, c(10, 10))
a =... | 72,027 |
<p>Suppose we perform a hypothesis test from a random sample $(x_i)_{i=1}^n$, assuming for instance $x_i \sim_{\text{iid}} {\cal N}(\theta, 1)$ and $H_0=\{\theta=0\}$ for simplicity. If the test fails to reject $H_0$, it is natural to ask oneself <em>"if I collect more data, what could happen?"</em>.</p>
<p>This quest... | 33,808 |
<p>I am trying to derive (one-sided) tolerance intervals related to the Deming regression model:
$$ x_i=x^*_i + \epsilon_i$$
$$ y_i = (\alpha+\beta x^*_i) + \epsilon'_i$$
where the $x^*_i$'s are nonrandom fixed numbers, $\epsilon_i \sim {\cal N}(0,\sigma_x^2)$, $\epsilon'_i \sim {\cal N}(0,\sigma_y^2)$, and all variab... | 72,028 |
<p>I have written some code that can do Kalman filtering (using a number of different Kalman-type filters [Information Filter et al.]) for Linear Gaussian State Space Analysis for an n-dimensional state vector. The filters work great and I am getting some nice output. However, the parameter estimation via loglikelihood... | 72,029 |
<p>I'm using R. My dataset has about 39 different Variables/Vektors and each has about 80 entries.Furthermore I have 1 Variable with 80 entries I want to maximize (lets call it Y). I assume that there are some correlations in my data and I want to find out what values my 39 variables should have in order for my Y to be... | 72,030 |
<p>Let the standard binary logit model with utility function:
Uni = Vni + eni, where eni obeys iid gumbel, and define Vni as:
Vni = a + xni*b.
where n denotes individual, and i denotes alternative.</p>
<p>Then, the elasticity of xni is given by:
Ei = b * xin * (1-Pni)</p>
<p>My question is if Utility function is not ... | 72,031 |
<p>I am currently getting $\prod x_i$ and $\prod (1-x_i)$ but a 1 dimensional sufficient statistic is asked for and considering that there is only a single parameter ($\alpha$), I think we should get a 1-dimensional sufficient statistic. I am not sure how to go about doing so though.</p> | 72,032 |
<ol>
<li>Is the central-limit-theorem true for all distributions?</li>
<li>For what sample size is it true (what is meant with "large")?</li>
</ol> | 44,821 |
<p>Suppose you have the logs of a web server. In these logs you have tuples of this kind:</p>
<pre><code>user1, timestamp1
user1, timestamp2
user1, timestamp3
user2, timestamp4
user1, timestamp5
...
</code></pre>
<p>These timestamps represent e.g. users' clicks. Now, <code>user1</code> will visit the site multiple ti... | 72,033 |
<p>I am using Caret function I have divided my data into training(75%) and test (25%) sets. Now I am running 10-Fold CV on training data. When i fit following model</p>
<p>train_control <- trainControl(method="cv", number=10)
output <- train(Species~., data=iris, trControl=train_control, method="rpart2")</p>
<p... | 72,034 |
<p>Given a model $a_{n}\cdot x^{n}+ a_{n-1}\cdot x^{n-1}+...+ a_0 = y + e$, where $e$ is some unknown (but assumed normally distributed) error and $x$ and $y$ are observations. </p>
<p>Now, how would one to estimate the confidence intervals of the coefficients $a_.$? </p>
<p>AFAIU, a simple procedure based on the c... | 37,826 |
<p>How can I take the cumulative sum of a 2D distribution, starting from the highest value in the distribution?</p>
<p>Background: my 2D distribution is the probability of different combinations of wave heights and wave periods based on measurements made at an ocean site. Assume the distribution shows that the most co... | 24,717 |
<p>I have a question about mediation when there is an interaction between 2 categorical variables, one with two levels and one with three levels.</p>
<p>Using the ‘mediation’ package by Tingley and colleagues in R, I’m trying to conduct a bootstrapped mediation analysis for an interaction between a 2-level categorical... | 72,035 |
<p>I have a small 20k (176 variables) test dataset. I want to create a random bigger dataset for testing, using the rows (data) and columns (names) from the small dataset.</p>
<p>Currently I have:</p>
<pre><code>real_data <- read.csv("somefilehere.csv")
# load one fake row so assignment of column names won't *ahe... | 72,036 |
<p>Can a confounding variable be correlated with the DV and not the IV?
I have heard of the DV being corr. but I can't find IV in any textbooks.
I found this def. in Wiki:
<a href="http://en.wikipedia.org/wiki/Confounding" rel="nofollow">http://en.wikipedia.org/wiki/Confounding</a></p> | 33,819 |
<p>I have a GLMM with a binomial distribution and a logit link function and I have the feeling that an important aspect of the data is not well represented in the model.</p>
<p>To test this, I would like to know whether or not the data is well described by a linear function on the logit scale. Hence, I would like to k... | 72,037 |
<p>I am trying to build a model where the response is a proportion (it is actually the share of votes a party gets in constituencies). Its distribution is not normal, so I decided to model it with a beta distribution. I also have several predictors. </p>
<p>However, I don't know how to write it in BUGS/JAGS/STAN (JAGS... | 38,246 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/21592/optimising-for-precision-recall-curves-under-class-imbalance">Optimising for Precision-Recall curves under class imbalance</a> </p>
</blockquote>
<p>I built a classification model and tested it again... | 49,886 |
<p>I am looking for a nice and formal way to define moving averages :</p>
<p>$y = \sum_{i=0}^N w_ix_i=<\mathbf{w},\mathbf{x}>$ </p>
<p>and especially the fact that weights have to equal one, i.e.
$\sum_{i=0}^N w_i=1$.</p>
<p>This property seems quite obvious to me, as you somehow want the output to have the... | 72,038 |
<p>Given $N$ data points in $\mathbb{R}^p$ - some of which are outliers (drawn from a different distribution from the inliers) - what sorts of algorithms have been designed to estimate the robust variance of this set? That is we would like to approximate the variance of the inlier space under some assumptions on the ou... | 10,184 |
<p>I've been putting a lot of work over the last few days into bring mixed effects models to bear on some behavioural data I've collected for my thesis, but it's occurred to me that I'm not 100% sure that this kind of model is actually appropriate for my data (I only came across them after starting the experiment).</p>... | 36,706 |
<p>I have a large symmetrical dissimilarity matrix of dimension 300 000. Can you please suggest the multidimensional scaling algorithms that can work with such large data? Input of course can be the original vectors from which the dissimilarity matrix was calculated.</p> | 33,821 |
<p>This is my first research assignment and I feel overwhelmed and confused.</p>
<p>I have been informed by my supervisor to do a hierarchical multiple regression using SPSS. I noticed that my dependent variable (DV) is ordinal. Is a hierarchical multiple regression correct or should I perform an ordinal (logistics)... | 72,039 |
<p>Reading about the Mann-Whitney test for simple random and independent samples I encountered a small issue. According to the book "Introductory Statistics" by Weiss, the test statistic is obtained using</p>
<p>$M = \text{sum of the ranks for sample data from population 1}$</p>
<p>As usual, we use this test statisti... | 33,823 |
<p>Papers like <a href="http://eprints.gla.ac.uk/4147/1/Briggs4147.pdf" rel="nofollow">Briggs et al. 2002</a> say that logical constraints on inputs such as probability parameters exclude the the Normal distribution from consideration due to its unboundedness. In this example, values below 0 and above 1. They briefly d... | 72,040 |
<p>A CLT says that asymptotically the sampling distribution of the sampling mean converges to the Normal. I would like to run a Monte Carlo simulation using information on one of the model's variables from the literature which reports some mean and standard error, but n=10. I am not comfortable assuming this n is large... | 72,041 |
<p>When you run a regression on ice cream sales with predictor shark attacks, you find a significant coefficient. But that is because there is a confounding variable temperature.</p>
<p>But how do you correct for this confounder? In case you also add temperature to the model, you have two correlated predictors and the... | 72,042 |
<p>I need an advice for plotting my results. I got different classification results by including different features and different k values. So, I got different results for each of them: </p>
<p>My features: alphaRaw16-1, alphaRaw16-2, alphaRaw16-3, grad-x, grad-y, grad-z.<br>
The range of k value: 1 to 21 </p>
<p>A... | 18,574 |
<p>I am looking for a C++ library for statistics to play with outliers detection in time series (amongst other). </p>
<p>What I need:</p>
<ul>
<li>Robust estimators, correlations, hypothesis tests, etc; </li>
<li>No dependencies with external libraries;</li>
<li>No GPL;</li>
</ul>
<p>Would be a plus:</p>
<ul>
<li>L... | 12,458 |
<p>Even though this is not directly a question related to statistical analyses, I thought this group might have some useful insights. My school windows-xp based workstation takes several hours to run simple logistic regression models with bootstrap corrections and bootstrap procedures for model selection (R code adapte... | 72,043 |
<p>For a pdf $f(x)$ (i.e. <strong>continuous</strong> distribution), Entropy (differential entropy) <a href="http://en.wikipedia.org/wiki/Differential_entropy" rel="nofollow">is defined</a> as:</p>
<p>$H_C(X) = -\int_\mathbb{X} f(x)\log f(x)\,dx.$</p>
<p>For a <strong>discrete</strong> distribution with p.m.f $F(x)$,... | 72,044 |
<p>I have a dataset with yearly levels of corruption in a number of countries, as well as whether they changed their government that year.</p>
<pre><code>year, corruption, change of president
2001, 5, 0
2002, 7, 1
2003, 8, 0
etc.
</code></pre>
<p>I want to test whether corruption is affected by a change in power (def... | 72,045 |
<p>People often talk about dealing with outliers in statistics. The thing that bothers me about this is that, as far as I can tell, the definition of an outlier is completely subjective. For example, if the true distribution of some random variable is very heavy-tailed or bimodal, any standard visualization or summar... | 72,046 |
<p>I would like to have a good idea on how to design clinical trials in oncology. In that issue, I am looking for a compact book that could give me a good overview, with the emphasis on statistical considerations.
Would you have a recommendation for me?</p>
<p>Thank you in advance,
Marco</p> | 33,826 |
<p>How should you deal with a cell value in a contingency table that is equal to zero in statistical calculations? (Note that such a value can be <em>structural</em>, i.e., it must be zero by definition, or <em>random</em>, i.e., it could have been some other value, but zero was observed.) </p> | 72,047 |
<p>I am referring to this tutorial: <a href="http://www.cs.cornell.edu/Courses/cs4758/2012sp/materials/hmm_paper_rabiner.pdf" rel="nofollow">A Tutorial on Hidden Markov Models and Selected Applications in Speech Recognition</a>. I am a bit confused about the forward algorithm.</p>
<p>From the tutorial:</p>
<blockquot... | 37,944 |
<p>In this talk <a href="http://videolectures.net/lms08_hardoon_scca/" rel="nofollow">http://videolectures.net/lms08_hardoon_scca/</a> (4:58) David says that maximizing the correlation between vectors can be viewed as minimizing the angle between them, and gives two references: Breiman & Friedman 1985, and Hastie &... | 72,048 |
<p>I am just wondering what does "to center two IVs" mean in the context of understanding an interaction. The IVs are A and gender and the DV is B.</p>
<p>Is it necessary for the main effects of a new interaction variable (A*Gender) to be a product (e.g. centered main effect of A * centered main effect of Gender) befo... | 44,864 |
<p>I have a lot of $N$ devices, and I'd like to know if any of them are faulty. What sample size do I need in order to make sure with $100(1-\alpha)\%$ confidence that none are faulty? </p> | 72,049 |
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