question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>So, as an example, let's say that I have data on a small auction that I conducted.<br>
Let's say I am selling a car and there are 5 bidders, and I have data on each of their bids, who won, who participated, etc. Now, let's say that I have 5 different cars, so the auction occurs 5 separate times. For example, in one ... | 72,801 |
<p>I wish to "predict" the number of bugs my company will cause using a linear regression. For any given piece of development, the prediction is not great ($r^2 = .2$). However, my real task is to predict, company-wide, how many bugs we'll produce in a week. My errors are roughly zero-mean, so in this aggregated data s... | 72,802 |
<p>I am performing a returns analysis. The idea is to regress a time-series of returns on the returns of various asset classes. The beta coefficients must be constrained such that sum of the coefficients is 1 and no coefficient is less than 0 or greater than 1. These beta coefficients can then be interpreted as explain... | 46,157 |
<p>I would like to use tslm with data that has intraday seasonality and a different pattern on business days and on non-business days.
If data.ts is my time series then I would like to use something like</p>
<pre><code>tslm(data.ts~season|businesss.dummy)
</code></pre>
<p>Thus I want to model season given that the du... | 72,803 |
<p>"Customers arrive at a bank according to a Poisson process with rate 6 per hour.</p>
<p>State (together with a proof) clearly the (conditional) probability mass function of the numbers of customers arrived during the first 20 minutes, given that 10 customers have arrived during the first hour."</p>
<p>I did this:<... | 72,804 |
<p>I don't know how many steps are necessary for <code>lars()</code> to select the variables till the algorithm proceeds to the saturated fit (especially using the <code>lars</code> package in <code>R</code>)? Can anyone give me a hint? </p> | 34,852 |
<p>Is there a paper or book that talks about the mathematical relation between different machine learning models - how they are different and how they can (sometimes) be equivalent? </p>
<p>For instance logistic regression can be viewed as a single-layer perceptron. Other examples are <a href="http://www.scholarpedia.... | 48,820 |
<p>My apologies is this is too rudimentary to be asked here. If it does not belong here, could someone recommend a more appropriate place to ask?</p>
<p>A little context. I am in a Senior Physics Lab class in college. Our first "experiment" involved rolling dice and calculating the probability of rolling each face. (T... | 72,805 |
<p>The necessary context is, I want to model the world as states, and a state is a frequency distribution of people's opinions. So I wonder if I can use a random variable, say $T$, to model the state the world is in and hence the frequency distribution. Thanks.</p> | 72,806 |
<p>I'm evaluating two (2) refrigerants (gases) that were used in the same refrigeration system.</p>
<p>I have saturated suction temperature ($S$), condensing temperature ($D$), and amperage ($Y$) data for the evaluation.
There are two (2) sets of data; 1st refrigerant ($R_1$) & 2nd refrigerant ($R_2$).</p>
<p>I'm... | 72,807 |
<p>I am new to the Path Analysis and ESM. I have been doing reading on this method, but still feel very much confused.</p>
<p>I have a empirically evaluated failure model having 45 variables connected with each other in a cause and effect model. In my models, there are total 40 failure path. The longest paths has as ... | 72,808 |
<p>Just to clarify, when I mean summary statistics, I refer to the Mean, Median Quartile ranges, Variance, Standard Deviation.</p>
<p>When summarising a univariate which is <strong>categorical or qualitative</strong>, considering both <strong>Nominal</strong> and <strong>Ordinal</strong> cases, does it make sense to f... | 72,809 |
<p>Is it possible to define any useful entropy or <a href="http://en.wikipedia.org/wiki/Conditional_entropy" rel="nofollow">conditional entropy</a> which is based on the distance between datapoint(s) and cluster center(s), instead of basing on the number of points assigned to cluster like it is defined in for example t... | 34,858 |
<p>I have a two-state HMM, in which my belief in emission probabilities depends on the observation. Basically, in addition to the two vectors of emission spectra (one for each state), I also have two vectors of priors that depend on parameters other than state "history". In other words, they have nothing to do with tra... | 72,810 |
<p>I'm trying to establish a bivariate Pearson correlation between two groups of variables in SPSS, however one of the groups has positive decimal numbers and the other negative decimal numbers.</p>
<p>The results show a significant negative correlation between the two groups. If the negative numbers were positive ins... | 48,734 |
<p>I am a beginner in statistics, and am self-studying from "Information Theory, Inference, and Learning Algorithms" by David MacKay. I've hit a wall with one of the questions, and was wondering if any of you could be so kind as to point me in the right direction. Admittedly, my title may be wrong or totally misleading... | 72,811 |
<p>I have a program to predict some values for people. For validation, I keep track of whether the prediction is correct or not, which gives me a binary vector with a length of about 600.</p>
<p>To test if it is significant above a random predictor, I created 100 random binary vectors of predictions for the same value... | 37,733 |
<p>I am a beginner in the field of forecasting. I wish to know which are the best tools that can be used for forecasting future values in a time series using genetic algorithms.</p>
<p>Are there any tools in MATLAB dedicated to forecasting using genetic algorithms similar to nntoolbox is dedicated to neural networks?<... | 6,634 |
<p>$X = AS$ where $A$ is my mixing matrix and each column of $S$ represents my sources. $X$ is the data I observe.</p>
<p>If the columns of $S$ are independent and Gaussian, will the components of PCA be extremely similar to that of ICA? Is this the only requirement for the two methods to coincide?</p>
<p>Can someo... | 72,812 |
<p>What would be an appropriate statistical test to determine the best model for two competing linear models?</p>
<p>Both models use the same independent variables (IVs); however, some independent variables are measured at different times. In the first model, the IVs lag the dependent variable (DV) by one period of ti... | 72,813 |
<p>Is it possible to manipulate a Poisson Distribution's $\lambda$ value such that it has a probability mass function that looks like the curve below with data points $(8,0)$,$(7,0.01)$,$(5,0.1)$ and $(2,1)$. I have been trying to obtain a $\lambda$ that will satisfy these values but have been struggling as the probabi... | 34,861 |
<p>Say I have a dataset $X = \{x_i\} \supset \mathbb{R}^n$ for which I assume that $x_i = y_i + \sigma(y_i)$ for some unobserved variables $\{ y_i \}$. That is, I believe that my data is subject to heteroscedastic noise.</p>
<p>From what I see, this rules out methods such as factor analysis.</p>
<p>I am currently sea... | 72,814 |
<p>From <a href="http://en.wikipedia.org/wiki/Wald_test" rel="nofollow">Wikipedia</a></p>
<blockquote>
<p>Under the Wald statistical test, the maximum likelihood estimate $\hat\theta$ of the parameter(s) of interest $\theta$ is compared with the proposed value $\theta_0$, ... In the univariate case, the Wald statist... | 72,815 |
<p>Stationary Wavelet Transform based denoising methods are considered the best because of their translational invariance. On the other hand, Matlab promises SWT based denoising but in the ddencmp function for denoising a signal, it is actually using Discrete Wavelet Transform when it should rather threshold the SWT co... | 72,816 |
<p>I'm attempting to make a simple mosaic generator, where it takes a photo, then uses hundreds of other photos to represent each pixel. To do so, I want to determine the dominant color of each picture I am using as a tile, so I can know what colors it can represent. I have an array containing the RGB values of each pi... | 34,865 |
<p>Assume that you want to approximate your joint distribution on set of variables via decomposing it into several smaller distributions. Assume that you don't know any prior knowledge about the statistical or algebraic connection between variables; the only input is a set of samples from variables. How do you claim wh... | 72,817 |
<p>I'm looking to investigate the relationship between a series of variables on a recurring basis.</p>
<p>One variable will always be the dependent variable, and will take three possible values: <code>good</code>, <code>bad</code>, or <code>other</code>, which I have coded as <code>1</code>, <code>-1</code>, and <code... | 72,818 |
<p>Assume there are $K$ people and iid. parameters $a_1,\ldots,a_K$ associated to them with $a_i \sim U(0,1)$. Person $i$ observes his own fixed $a_i$ with some noise:
\begin{equation}
X^{(1)}_i= a_i+ e^{(1)}_i,
\end{equation}
where the $e_i$ is an error terms distributed normally with $N(0, v)$. He learns $X^{(1)}_i... | 72,819 |
<p>I want to measure metacognition (as a whole construct and per subscale, (knowledge of cognition (KC)) and regulation of cognition (RC)) development in children using the Jr MAI inventory. The Jr MAI has two version, version A (for 9-11) and B (for 13-15), version A has 3 point Likert scales and version B has 5 point... | 41,867 |
<p>I have several datasets in R+, each containing two training and test sets. For example the following <a href="http://i.imgur.com/I1fx2kB.png" rel="nofollow">dataset</a>. I want to train a classifier by using training data such that by applying the test data, I get some reasonable number of points as anomaly so that ... | 49,906 |
<p>I'm trying to differentiate experimental data which are measured with time. However, the time increments are not equally spaced.</p>
<p>I first obtained a trend line for these data and then did a linear interpolation to obtain equally spaced points. Then I used central differencing to obtain the derivative. However... | 34,871 |
<p>I have been using R to calculate logistic regression with many independent variables for a Ruby on Rails web application. However, I can no longer import data from the database to R using RPostgreSQL. The web host has stopped allowing insecure connections to the database. The point is, I either need to get a new web... | 46,178 |
<p>I am using logistic regression to analyze some categorical data (binary response variable and categorical -- mostly binary -- predictor variables). For my model, I have something like <code>A ~ B</code> and a hypothesis that the respondent's <code>B</code> has some explanatory power over the choice of <code>A</code... | 49,606 |
<p>I have data from a survey experiment in which respondents were randomly assigned to one of four groups:</p>
<pre><code>> summary(df$Group)
Control Treatment1 Treatment2 Treatment3
59 63 62 66
</code></pre>
<p>While the three treatment groups d... | 49,606 |
<p>I am currently working with gene expression data where I have a number of genes (variables) measured over a number of samples. I could not make sense of the statistics and visualization suite we have, so I started checking out the tutorial and came up with the following bit:</p>
<blockquote>
<p>You specify a lowe... | 34,878 |
<p>I know the significance of the slope of a LMS linear regression can be calculated using the r2 coefficient of determination and looking up the appropriate value in an F table. However, I was thinking of perhaps making this "more robust" by replacing the LMS linear regression with a repeated median straight line fit,... | 37,514 |
<p>Lets say I have an R value of .5 and therefore an $R^2$ value of .25, and a p value < 0.001. (All through the stock cor.test function in R).</p>
<p>Is there a way to isolate those cases/observations whose variation is most explained by my $R^2$? My goal is two fold, find the group for which this correlation is m... | 315 |
<p>I would like to provide an intuitive visualization of my database for readers and users of the database that does not require technical knowledge of database structure. The figure will be included in a journal article, and the audience is primarily students and scientists, many of whom will not understand concepts s... | 549 |
<p>I apologize in advance... there's a good amount of stuff to read before you get to my question. Maybe I could have saved a word or two here and there... but overall, the background (I think) was required in order to best illustrate the topic. </p>
<p>Ok, I recently purchased SPSS in support of an upcoming resea... | 72,820 |
<p>I am trying to understand the exact difference between Taxonomy and Classification with respect to data/text mining. </p>
<p>I would appreciate it if you could explain with a simple example. </p> | 72,821 |
<p>In the <code>R</code> package <code>hdrcde</code> by Rob Hyndman for Computation of highest density regions in one and two dimensions, the hdrbw function Estimates the optimal bandwidth for 1-dimensional highest density regions.</p>
<p>In the given example, HDRlevelVal variable is a probability 0
<p>HDRlevel : HDR... | 34,887 |
<p>Given a series of values, I know that 68% of the values fall withing one standard deviation and that 95% fall withing 2 standard deviations, but how do I calculate the range whereby 90% percent of the values will fall. Lets call that 90% range the typical range. </p> | 72,822 |
<p>The question above says it all. Basically my question is for a generic fitting function (could be arbitrarily complicated) which will be nonlinear in the parameters I am trying to estimate, how does one choose the initial values to initialize the fit? I am trying to do nonlinear least squares. Is there any strategy ... | 72,823 |
<p>In e-commerce site, consumers would provide a overall rating with multi-aspect ratings. For example, if a consumer purchase a camera, he would provide a rating info as follows:</p>
<pre><code>User Product Size/Wight Appearance Battery Price Display Overall
A Camera 1 4 2 ... | 72,824 |
<p>Im looking for some pointers on which topics I should be looking into in order to identify periods (of non fixed length) which deviate from randomness. I have a feeling hypothesis testing may be what I'm looking for though I haven't covered it yet. My stats knowledge is limited hence any suggested books / websites w... | 72,825 |
<p>Consider the training set $\{(x_i; y_i)\}_{i=1}^N, x_i \in \mathbb{R}^n, y_i \in \mathbb{R}$.</p>
<p>The goal is to find regression function, like, $f(x) = \sum_{i=1}^K a_i g_i(x) + a_0$.
The least-squares solution is well known, if we know $g_i$ functions.</p>
<p>Lets consider that we have kernel regression with ... | 72,826 |
<p>I am probably looking for a definition.</p>
<p>Imagine we have 10 variables, but we are not interested in some kind of linear relation (nor quadratic or with any curve to it). What I would like is a way to find "clusters" , patterns or combinations (whatever you want to call it). For instance, given 10 variables, l... | 168 |
<p>Lets say I have a $p$-dimensional multivariate Gaussian distribution. And I take $n$ observations (each a $p$-vector) from this distribution and calculate the sample covariance matrix $S$. In this <a href="http://amstat.tandfonline.com/doi/full/10.1198/jasa.2011.tm10155">paper</a>, the authors state that the sample ... | 34,892 |
<p>In <a href="http://link.springer.com/article/10.1007/BF00133443#page-1" rel="nofollow">Manski - The structure of random utility models</a> the following example is proposed:</p>
<p>Consider the alternative set space <strong><em>a</em></strong> = $(\alpha,\beta,\gamma)$ with the attribute representation: $X = \begin... | 34,893 |
<p>A while back, I did some educational research where I compared exam scores between two groups. I remember reading somewhere that educational exams such as these tend to follow a normal distribution. Of course, normal distributions must necessarily be infinite and educational exam scores are not. Is it mathematica... | 34,894 |
<p>(Apologies for the cross-posting from math.stackexchange.com; I wasn't aware of this site until just now).</p>
<p>I would like to test the performance of two algorithms. The second is a variant of the first. There is no prior data on the performance of either in a particular domain. The performance of both on any g... | 72,827 |
<p>I am using a support vector regression is order to get estimates of a variable y.
I want to receive a probability distribution of my estimates and not just point estimates.
I want to predict Gaussian Distributions for every point where the mean should be my point and I will also give a variance.</p>
<p>What I am th... | 30,936 |
<p>I am working on an imbalanced classification problem where target to non target ratio is around 1% to 99%. Since it is an imbalanced classification problem, I have tried one strategy using SMOTE package in R. Before that additional derived variables were also added to the SAS dataset as well as some proxy business r... | 24,115 |
<p>If $ X_1, ... ,X_n$ are IID binomial with parameters $ n$ and $p, $ find an unbiased
estimator for</p>
<p>$$G(p)=P(X_1=1)=np(1-p)^{n-1}\, .$$</p>
<p>I need to find this estimator so I can apply Lehmann-Scheffé theorem. I think it can't be a "crazy" estimator. But I couldn't find anything. Can I have a hint?</p>
... | 72,828 |
<p>Rob Tibshirani propose to use lasso with Cox
regression for variable selection in his 1997 paper
"The lasso method for variable selection in the Cox
model" published in Statistics In Medicine 16:385.
Does anyone know of any R package/function or syntax in R that
does lasso with a Cox model?</p> | 72,829 |
<p>I want to test the hypothesis of a decreased level of vitamin D in diabetic subjects. For this I have recorded blood glucose and vitamin D levels in 40 cases and 40 controls. </p>
<p>What kind of statistical test can I use to the above hypothesis?</p> | 34,898 |
<p>I'd like to test the <em>anova rbf kernel</em> included in the <strong>kernlab</strong> package in <strong>caret</strong>. Following excelent tutorial (<a href="https://topepo.github.io/caret/custom_models.html" rel="nofollow">https://topepo.github.io/caret/custom_models.html</a>) I've come up with the following cod... | 72,830 |
<p>I have some data in the range [0, 1], and from the histogram below, it seems that they might be drawn from a distribution with linear probability density function (what's the name of that kinds of distribution?). How do I estimate the parameters of that distribution and how do I test how likely the data were drawn f... | 72,831 |
<p>Data are collected in a clinical trial evaluating a new compound designed to improve wound healing in patients. The new compound is compared against a placebo. After treatment for 5 days with the new compound or placebo, the extent of wound healing is measured and the data are shown in Table. Suppose that the clinic... | 46,205 |
<p>I've been reading a lot on the effect of perceptual load on selective attention but the analysis confuses me somewhat. Some of these studies flag 20-40ms differences between conditions as significant where the mean is about 500ms and my gut tells me something is fishy. Unfortunately, almost no one reports any inform... | 72,832 |
<p>I'm using a wild bootstrap to create confidence intervals around fitted values of the following model, for a specific combination of the factors, as x varies across its range.</p>
<pre><code>mod = gam(log(lhs)~ s(re,bs="re",by=dum)
+ as.factor(fac1)
+ as.factor(fac2)
+ as.factor(fac3)
+ s(x,... | 72,833 |
<p>I've been trying to teach myself about Network Analysis, and I've been able to develop DAG charts in R. However, I've looked through three or four R packages and have seen little in the way to a function to generate joint probabilities for the network. The DAG plot tells me about the variables in relation to one ano... | 34,904 |
<p>I am trying to create a custom likelihood function that uses different likelihood functions depending on whether an observation is endogenous or exogenous. Is it possible to hardcode my function using the link variable in the <code>glm</code> function in the <code>glm</code> package? Or would I have to do everything... | 34,905 |
<p>When doing ANCOVAs, software usually gives both unadjusted means as well as adjusted means. However, the post hoc tests for most statistical programs are limited to unadjusted means. Yet, sometimes, if one is doing an ANCOVA, post hoc comparisons of adjusted means is what is desired, not the unadjusted comparisons. ... | 34,907 |
<p>I am trying to implement the following paper: <a href="http://jmlr.csail.mit.edu/papers/v5/lanckriet04a.html" rel="nofollow">Learning the Kernel Matrix with Semidefinite Programming</a> using <a href="http://cvxr.com/cvx" rel="nofollow">cvx</a> toolbox for matlab. My question is about how exactly I can use this meth... | 72,834 |
<p>I am using a probit and a logit model for obtaining the choice probabilities of some data. What kind of plots can be useful to conduct a exploratory data analysis for these data?</p>
<p>Here is the simulated data:</p>
<pre><code>set.seed(1)
x.first <- rbinom(1000,1,0.5)
x.second <- rbinom(1000,1,0.5)
y <-... | 39,568 |
<p>When working with markov chain monte carlo to draw inference, we need a chain that mixes rapidly, i.e. moves throughly the support of the posterior distribution rapidly. But I don't understand why we need this property, because from what I understand, the accepted candiate draws should and will concentrated in the h... | 22,542 |
<p>I'm trying to do a simple least-squares fit on some data. The formula is simply:</p>
<p>$Y = C_0X_1 + C_0X_2 + C_0X_3 + C_0X_4 + C_0X_5$</p>
<p>I have 24 rows of $Y$'s and $X$'s, and I'm trying to fit the $C$'s.</p>
<p>The problem, however, is that I need to constrain the ranges of the $C$'s to be non-zero, regar... | 72,835 |
<p>I’m studying the Restricted Boltzmann Machine (RBM) and having some issues understanding log likelihood calculations w.r.t. parameters of the RBM.
Even though a lot of research papers on RBM have been published, there are no detailed steps of the derivatives. After searching online I was able to find the following ... | 34,912 |
<p>1) What is the threshold or measure to say that the variation of data is high? Typically we say high or low variation by comparing with another data set. But there is only one data set.</p>
<p>2) We can use boxplot to visualize standard deviation, mean, etc., of the data. However, I am curious to know whether there... | 72,836 |
<p>I am reading Hinton's paper "Training Products of Experts by Minimizing Contrastive Divergence" about training PoE. There is an explanation of PoE's expressiveness, which stats "because the posterior distribution cannot be sharper than the individual
models in the mixture and the individual models must be broadly tu... | 46,216 |
<p>I am new to SPSS, and am trying to use SPSS to generate a variable on the quality of health service available to the residents of an area. Below are the categorical variables that could tell me the quality of health available to them. </p>
<ul>
<li>no insurance covering health care cost </li>
<li>no access to ambul... | 72,837 |
<p>I am trying to calculate the $R^2$ value for a production constrained spatial interaction model, using <a href="http://books.google.com.au/books?id=6OLrAAAAMAAJ" rel="nofollow">Fotheringham and O'Kelly (1989)</a> as my guide. </p>
<p>I get dramatically different values for R-Square, depending on whether I calculate... | 34,915 |
<p>In answer to a question on <a href="http://stats.stackexchange.com/questions/25611/how-to-deal-with-collinearity-issue-when-performing-variable-selection">model selection in the presence of multicollinearity</a>, <a href="http://stats.stackexchange.com/users/4253/frank-harrell">Frank Harrell</a> <a href="http://stat... | 34,916 |
<p>Given data following a Bernoulli distribution $Y_1,...Y_n \sim B(1,p)$, we want to measure $\theta = \text{Var}(Y_1)$</p>
<p>I found this unbiased estimator $S^2 = \frac{\sum{(y_i-\bar{y}})^2}{n-1}$</p>
<p>I need to improve this estimator using the Rao-Blackwell theorem and determine if the new estimator is UMVUE ... | 72,838 |
<p>consider the following example data:</p>
<pre><code>df1 <- data.frame(customer=c(rep("customer1",5),rep("customer2",10),rep("customer3",7)),
money_spent=sample(22))
df2 <- data.frame(customer=c("customer1","customer2","customer3"),
origin=c("US","US","UK"),
... | 34,917 |
<p>If I need to build yield curve, n what is the minimum number of data points necessary for any interpolation method, e.g. say cubic spline or Nelson–Siegel, etc.</p>
<p>I ma not sure if I can raise this query here, but if someone can guide, it will be a great help.
Thanks.</p> | 72,839 |
<p>I fitted a GEE model using the function <code>genZcor</code> with user defined
correlation matrix. I want to get the var-cov matrix of the regression
coefficients. But the output provides only limited information.</p>
<p>I would be very much thankful if you could kindly let me know how to get
it since I am struggli... | 46,220 |
<p>This is basically a modified version of a previously unanswered question I posed <a href="http://stats.stackexchange.com/questions/31937/how-to-get-p-value-for-indirectly-generated-random-variables">here</a>, as I'm starting to have second thoughts about my methodology.</p>
<p>In summary, I have four random variabl... | 72,840 |
<p><strong>Is there an algorithm that returns the mean probability of response from a multi-dimensional matrix?</strong></p>
<p>For example, if I have a set of features:</p>
<ul>
<li>customerClass = <code>poor</code> / <code>middle</code> / <code>rich</code></li>
<li>category = <code>11</code> / <code>20</code> / <co... | 72,841 |
<p>I have to generate multivariate gamma distributions with given positive-definite covariance matrix. Anyone can suggest me a method?</p>
<p>Thanks,</p> | 22,568 |
<p>I have been teaching myself about Gaussian Process (GP) modeling for a while now and although it is "easy" to estimate the range parameter (sometimes called the length-scale) in the GP I am actually trying to gain a physical understanding/intuition for what the range parameter actually represents. Just so that my q... | 34,923 |
<p>I'm studying the growth of a population (users of a website).
I have the user count for each time block (which is 2 weeks long).
Now, I'd like to understand if this growth follows a well-known growth curve.
To start with, I ran this regression on R on 30 observations with <code>glm(tot_users ~ block_id,family=binomi... | 72,842 |
<p>I am using the bootstrap algorithm to compute standard errors of the estimates of my normalmixEM output. I am not really sure if they are reliable?</p>
<p>My code is (data <a href="http://www.sendspace.com/file/80tr5g" rel="nofollow">here</a>):</p>
<pre><code># load package
install.packages("mixtools")
library(mix... | 34,924 |
<p>The variance of a set of $n$ binary variables $D = <x_1, \ldots, x_n>$ is
$$
{\rm var(D)} = \frac{k(n-k)}{n^2},
$$
where $k$ denotes the number of $1$s in $D$ (see <a href="http://capone.mtsu.edu/dwalsh/VBOUND2.pdf" rel="nofollow">http://capone.mtsu.edu/dwalsh/VBOUND2.pdf</a>).</p>
<p>With Matlab the variance... | 34,926 |
<p>Krippendorff has a paper (<a href="http://repository.upenn.edu/cgi/viewcontent.cgi?article=1042&context=asc_papers" rel="nofollow">free</a> and <a href="http://link.springer.com/article/10.1007%2Fs11135-004-8107-7" rel="nofollow">official</a> versions) describing an adaptation of his measure of reliability α to ... | 34,930 |
<p>And what is the optimal method to do this? Is there a package for this in R?</p> | 49,907 |
<p>Sorry, I'm not an expert and my question could be fundamentally wrong.
I've read this interesting <a href="http://stats.stackexchange.com/questions/11602/training-with-the-full-dataset-after-cross-validation">question</a> because I also was wondering whether to train the model again after cross-validation.</p>
<p>N... | 72,843 |
<p>I have been struggling to fit the following problem into a linear state space model for a Kalman Filter (KF). I'm having a hard time seeing what I'm doing wrong. I suspect I'm violating some law of KF state space modeling. Perhaps something is non-gaussian, non-linear, non-kosher?</p>
<p>I have data from players wh... | 72,844 |
<p>This is a quite simple question but I don't find any good, clear, precise answers:
I'm looking for a way to perform <em>post hoc</em> test on a chi$^2$ test.</p>
<p>I have 2 variables : var1 : good/fair/poor and var2: a/b/c</p>
<p>This is the contingency table :</p>
<pre><code> a b c
good 120 70 13
fair ... | 72,845 |
<p>When performing Missing Value imputations, should we be concerned about overfitting the data? Why or why not? For example: If I impute a variables missing value using a CART regression tree, should I be concerned about my tree being too complex and overfitting that particular data? When it comes time to use test... | 72,846 |
<p>I've been calculating characteristic functions and MGF's and was wondering whether we can always get the characteristic function simply by substituting $it$ instead of $t$ in the resulting equation. For example the normal MGF is
$
\exp{(\mu t + \frac{\sigma^2 t^2}{2})}
$
but if we substitute $it$ into that we get $
... | 49,908 |
<p>I run k-means clustering on my dataset (100 samples in total) and partition the data into k=5 clusters. Then I want to test how robust of the k-means can be; however, I haven't got more new data samples. My idea is:</p>
<ul>
<li>Take the first sample out and run k-means on the rest of 99 samples.</li>
<li>Loop over... | 685 |
<p>I have a 2x2 contingency table and i want to calculate if the pair inside is significantly different.
i made a matrix like the following named raw_matrix </p>
<pre><code> CNS random
Not_H3K4 343 28825
H3K4 11 2014
</code></pre>
<p>Create this matrix , thus:</p>
<pre><code>raw_matrix = structure(... | 72,847 |
<p>I was running some analysis where I suspect that a treatment $D$, has opposite effects on two variables $Y^A$ and $Y^B$. To show that, I was thinking about two strategies:</p>
<p><strong>1. Differencing</strong></p>
<p>Running the regression using the difference between $Y^A$ and $Y^B$ as my dependent variable, na... | 72,848 |
<p>do we have any proc or way that we can apply a model built on train dataset to test dataset using the predict function similar to R in SAS?</p> | 72,849 |
<p>I am working on a research project where I have several questions from a survey data that measures the same underlying quantity (my dv), possibly each with some measurement error.
I was thinking about using PCA method to extract the most relevant component. My initial analysis turns out to give what I wanted, but I'... | 72,850 |
<p>First, I have a question about whether the Poisson distribution is "stable" or not. Very naively (and I'm not too sure about "stable" distributions), I worked out the distribution of a linear combination of Poisson distributed R.V.'s, using the product of the MGF. It looks like I get another Poisson, with parameter ... | 72,851 |
<p>$F$ is the distribution function of a positive random variable.
Why does the following hold for every $x \in (0,\infty)$:</p>
<p>$F^{*2}(x) \leq F^2(x)$, where</p>
<p>$F^{*2}=F*F=\int\limits_0^x F(x-y)dF(y)$</p> | 38,043 |
<p>I am asking to find out why a factor may become non significant after I define the nested design. The following are the two aov analysis in R.</p>
<p>Obs (subject #) is the within subject factor and stim3 & label (1st & 2n stimuli manipulations) are the nested within subject. stim3 & label are nested w... | 42,247 |
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