question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I'm trying to build a content-control (web filtering) application using machine learning (just for training purposes). For example define gaming sites. I'm somewhat familiar with machine learning algorithms, but I have almost no idea how to get features from HTML pages. Can anyone suggest any good material? Maybe s... | g68133 | [
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<p>I have two time series, which by looking at they appear to be correlated i.e. when one is high the other is high, and when one is low the other is low. Besides looking at the figure and saying these are correlated, I am looking for a statistical approach to assess whether these two time series are correlated or not.... | g27993 | [
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<p>I am building a whiteboard to track the position of its pen. I have <code>n</code> ultrasound receivers placed on the periphery of the whiteboard, and an ultrasound emitter in the pen. The pen emits pulses the receivers detect. A microprocessor gathers the arrival times of the pulses for each receiver, and makes an ... | g68134 | [
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<p>I have an exemplar grouping of objects (each with their own feature vector) into categories. I am then given a new grouping of compeltely different objects, and Iw would like to compute the probability of this grouping being 'correct'.</p>
<p>I realise this is a tricky problem, so I have tried to break it down a li... | g68135 | [
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<p>Which test should I use, if I want to test the correlation between 2 bivariate grouped variables?</p>
<p>The case is: I have asked several hotel owners about their feelings about the occupational rate of their hotel and the propagation of the region, where the hotel is. Both of the questions had ordinal scales, spr... | g48826 | [
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<pre><code>m <- matrix(nrow=5, ncol=5)
m <- ifelse(row(m)==col(m), 1, 0.4)
ch <- chol(m) # Choleski decomposition
u <- matrix(rnorm(2000*5), ncol=5)
uc <- u %*% ch
cr <- pnorm(uc)
cr <- qbinom(cr,1,0.5)
cor(uc)
cor(cr)
</code></pre>
<p>The cor(uc) is 0.4. However, I also expe... | g37441 | [
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<p>I am building a .NET program. One of its functions is to provide a predictive model for a vehicles life-to-date maintenance costs, basically what is the cumulative cost(Y) for a vehicle at specific year(X). I decided to use a 2nd degree polynomial least squares fit and for the most part it does a good job. Sometimes... | g68136 | [
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<p>My questions deals with GAMs in the <strong>mgcv</strong> R package. Due to a small sample size I want to determine the prediction error using leave-one-out cross-validation. Is this reasonable? Is there a package or code how I can do this? The <code>errorest()</code> function in the <strong>ipred</strong> package d... | g68137 | [
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<p>I've poked around a bit in the Cross Validated archives and haven't seemed to find an answer to my question. My question is the following: Wikipedia gives three assumptions that need to hold for the Wilcoxon signed rank test (slightly modified for my questions):</p>
<p>Let Zi = Xi-Yi for i=1,...,n.</p>
<ol>
<li><p... | g27996 | [
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<p>Anybody have any experience with software (preferably free, preferably open source) that will take an image of data plotted on cartesian coordinates (a standard, everyday plot) and extract the coordinates of the points plotted on the graph?</p>
<p>Essentially, this is a data-mining problem and a <strong>reverse</st... | g49693 | [
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<p>I have a regression where I am trying to predict Y, using several variables. My variables are A, B, C. </p>
<p><img src="http://i.stack.imgur.com/9Qg6q.png" alt="enter image description here"></p>
<p>I'm using <code>R</code> for my analysis. My equation is as follows:</p>
<pre><code>mod <-lm( log(Y/B) ~ log(A... | g27998 | [
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<p>As a background, I am not familiar with stats except on a basic level. I have been tasked with doing some analysis that is out of my comfort zone.</p>
<p>I am trying to figure out how to compute necessary sample sizes for an ROC analysis based on desired statistical power. I have read Hanley and McNeil's paper (<a ... | g35892 | [
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<p>Suppose we have several documents. These docs are classified into several categories. But there could be issues like these:</p>
<ul>
<li>The categories may not be properly defined.</li>
<li>Or The categories are
properly defined, but the docs are not properly classified.</li>
</ul>
<p>Given the category definition... | g68138 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/5450/what-if-interaction-wipes-out-my-direct-effects-in-regression">What if interaction wipes out my direct effects in regression?</a> </p>
</blockquote>
<p>I have three hypotheses within my experiment, an... | g49395 | [
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0.01... |
<p>I found a reference in an article that goes like:</p>
<blockquote>
<p>According to Tabachnick & Fidell (1996) the independent variables with
a bivariate correlation more than .70 should not be included in
multiple regression analysis.</p>
</blockquote>
<p><strong>Problem:</strong> I used in a multiple re... | g49567 | [
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... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/37845/two-negative-betas-in-a-curvilinear-regression-when-mean-centered-or-using-stan">Two negative beta's in a curvilinear regression when mean centered or using standardized values</a> </p>
</blockquote... | g49795 | [
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<p>I need a good reference for the methods and/or the difficulties that arise when attempting such a combination.</p>
<p>I've found Loughin, TM, <a href="http://www.sciencedirect.com/science/article/pii/S0167947303002950" rel="nofollow">A systematic comparison of methods for combining p-values from independent tests</... | g28004 | [
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<p>What is the most optimum method to calculate the median in a distributed setting? I want to optimize with respect to data transmission i.e. an algorithm that finds the median across data spread across multiple nodes by sending the least amount of data</p> | g68139 | [
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<p>I plan to execute a little study on whether dentists tend to grant privately insured patients (PRIV) a sooner appointment compared with publicly insured patients (PUB). I want to restrict this study to the dentists of a single town in Germany.</p>
<p>In this town there are about 500 dental practices and I am willin... | g68140 | [
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<p>Following on from <a href="http://stats.stackexchange.com/questions/13757/how-do-i-weigh-several-variables-at-two-levels-to-create-an-overall-composite-var/13790">my previous question</a> on forming scale scores, my sample has 100 people who have answered 10 likert scale questions each on two academic subjects: Math... | g37461 | [
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<p>i ran exploratory factor analysis and according to eigenvalue > 1, 41 factors were extracted out of 142 items. but when i ran MAP and parallel analysis, 16 factors were prescribed as a proper number of factors to retain. now what should I do? With 16 factors, my total variance is 51% and with 41 factor, total varian... | g28011 | [
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<p>I have this presence/absence matrix (S2 is missing on purpose).</p>
<pre><code>dat <- read.table(text="S1 S3 S4 S5 S6 S7 S8 S9 S10
0 0 1 1 0 0 1 0 0
0 0 1 1 0 0 1 0 0
0 0 1 0 0 0 0 0 0
0 0 0 1 0 0 0 0 1
0 0 1 1 0 0 1 0 0
0 ... | g68141 | [
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<p>I want to combine three unbound variables. Each variable is the score provided by three different algorithms. Each algorithm predicts the likelihood (score) that a specific interaction between two molecules takes place. I have a gold standard with which I can rate the performance of each algorithm (that is, how many... | g48850 | [
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<p>Let $X_{1},..,X_{n}$ be a sample from a poisson$({\lambda})$ distribution. Let the prior be ${\pi}({\lambda})=1/{\sqrt{\lambda}}$. Find the posterior distribution.</p>
<p>My work: We have $f(x|{\lambda})=\frac{{\lambda}^{x_{1}+..+x_{n}-0.5}e^{-{\lambda}n}}{x_{1}!....x_{n}!}$. To find the marginal density I believe ... | g68142 | [
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<p>I am trying to determine whether a baseball player has the ability to influence the outcome of an "at bat" by calculating the correlation coefficient between the percentage of at bats which result in a given outcome from one year to the next, for each player-year in the sample.</p>
<p>For example, suppose that an a... | g28014 | [
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<p>I am fitting a basic generalized linear model (binomial) to some survey data that has a small sample size (N=376). The model my colleague has fit has 23 model parameters. Two or three have p-values less than 0.1.<br>
There are theoretical reasons to expect that those particular independent variables are linked to ... | g68143 | [
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<p>For a given input into the input nodes, there are multiple correct values for the output nodes. In the training set, there are times when the inputs result in a certain output, and other times when the inputs result in a completely different (but equally valid) output.</p>
<p>Will a neural network still be able to ... | g68144 | [
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<p>I have a dataset of Facebook users and a set of different clustering algorithms. The project goal is to draw up a rank between these algorithms in order to understand which of them are the good ones. The only information I have is the users dataset and nothing else: no ground-truth, no class / truth labels or whatev... | g68145 | [
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<p>I am not sure if such a beast exists, but is there some non-superiority test for a oneway ANOVA of $k$ groups, probably based on a $\Delta^{2}$ equivalence threshold, for $m=\left[k(k-1)\right]/2$ <em>post hoc</em> pairwise tests for equivalence (using the two one-sided tests procedure) based on an equivalence thres... | g28015 | [
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<p>My question concerns trying to justify a widely-used method, namely taking the expected value of Taylor Series. Assume we have a random variable $X$ with positive mean $\mu$ and variance $\sigma^2$. Additionally, we have a function, say, $\log(x)$.</p>
<p>Doing Taylor Expansion of $\log X$ around the mean, we get
$... | g68146 | [
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<p>I took the original Stanford AI course and got an immense amount out of it. I got a poor score since I did not have a great deal of time to work out all the problems.. But what I really enjoyed about the course was getting a grasp of the new techiques, way beyond the conventional statitistcs..</p>
<p>I'm looking fo... | g39878 | [
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0.011332745663821697,
0.008707260712981224,
-0.021628184244036674,
-0.04970591515302658,
-0.002175059635192156,
0.06428908556699753,
0.026172205805778503,
0.12470204383134842,
0.0... |
<p>(5 points) Assume that we are interested in generating a model (e.g., a decision tree) from a
sample of examples of a specific size drawn from some distribution. Assume further that we
would like to investigate how sensitive the resulting model is to the actual choice of training
examples (i.e., how the performance ... | g28016 | [
-0.02997385710477829,
0.029398692771792412,
0.021929867565631866,
-0.03743942826986313,
0.02567155472934246,
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0.02778458222746849,
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0.053136397153139114,
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0.0024505099281668663,
0.03612729534506798,
0.0377... |
<p>I have a model of total reaction time T, which is a composite of a selection time S and a discrimination time D. So a person first finds something, this takes the tS. Then he discriminates and reports an attribute of this thing, this takes the time D. We only measure the total time T, though. So, my model for T is:<... | g68147 | [
0.0011858951766043901,
-0.012494169175624847,
-0.009330140426754951,
-0.024702226743102074,
0.02002161741256714,
-0.01508312951773405,
0.051187288016080856,
0.06666256487369537,
-0.007491489872336388,
0.004744267091155052,
-0.047817621380090714,
-0.01204613596200943,
0.0007786155329085886,
... |
<p>Is it possible to have a variable that acts as both an effect (measurement) modifier and a confounder for a given pair of risk-outcome associations?</p>
<p>I'm still a little unsure of the distinction. I've looked at graphical notation to help me understand the difference but the differences in notation are bewilde... | g68148 | [
0.0019484509248286486,
-0.01802023872733116,
0.01062395703047514,
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0.00021881853172089905,
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-0.028293397277593613,
-0.004577740095555782,
0.007370656821876764,
0.06785539537668228,
0.01... |
<p>I have a dataset, consisting of two independent variables each with two levels.</p>
<p>The independent variables are individuals (1 vs. 2) and light (day vs. night) The dependent variable is the efficiency to detect an object (in other words the proportion of objects detected in a known population of objects). I wa... | g47315 | [
-0.013199265114963055,
-0.02551102824509144,
0.00008913423516787589,
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-0.03867317736148834,
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0.037037476897239685,
0.007977208122611046,
-0.014806185849010944,... |
<p>From <a href="http://en.wikipedia.org/wiki/Linear_congruential_generator#Advantages_and_disadvantages_of_LCGs" rel="nofollow">Wikipedia</a></p>
<blockquote>
<p>if an LCG is used to choose points in an n-dimensional space, the
points will lie on, at most, $m^{1/n}$ hyperplanes (Marsaglia's Theorem,
developed b... | g28017 | [
0.037127550691366196,
0.034013714641332626,
-0.0216149240732193,
-0.03736690804362297,
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-0.018400656059384346,
0.04907897487282753,
-0.003498571226373315,
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-0.04024471342563629,
-0.032877661287784576,
0.03702699393033981,
-0.011299217119812965,
0... |
<p>I have survey data from students from two Universities. One of the questions in the survey had 4 response categories and students were allowed to check only one (categorical variable).</p>
<p>I want to make a table that shows the odds ratio and 95% CI for OR with University arranged in columns and all 4 possible an... | g68149 | [
-0.040188081562519073,
0.004369891714304686,
-0.026608237996697426,
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0.0005773400189355016,
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0.0022126033436506987,
0.019418315961956978,
-0.018184881657361984,
-0.015267319045960903,
0.06097378209233284,
-0.019304173067212105,
0.07406049966812134,
... |
<p>I've collected around 10 numbers of ants from a colony and introduced the same numbers of ants to the same colony (say Colony-1) at their entrance to see their behaviour (whether they accepts or rejects). Again I introduced 10 ants from different colony (say Colony-2, i.e. non-nestmate) to Colony-1 and checked th... | g919 | [
-0.0021881980355829,
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0.015355539508163929,
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0.018458040431141853,
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0.025553347542881966,
0.06001053750514984,
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-0.017803525552153587,
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0.0353371687233448,
0.060292888432741165,
0.0449... |
<p>Is there an intuitive explanation for how SVD is related to co-clustering when performing SVD on a covariance matrix?</p>
<p>(i.e. the SVD is performed on the matrix $E[X Y^{\top}]$ where $X \in \mathbb{R}^n$ and $Y \in \mathbb{R}^m$.)</p>
<p>How does the projections $U$ and $V$ in the decomposition $U \Sigma V^{\... | g28027 | [
0.06621069461107254,
0.014542636461555958,
-0.018838290125131607,
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0.021304424852132797,
0.025781290605664253,
0.02362154610455036,
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0.009206854738295078,
0.0009209104464389384,
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0... |
<p>Pearson's R Value shows the correlation of two arrays of real numbers. I would like to calculate an correlation value for text which is associated with numbers then a P value to judge the statistical significance of this relationship. Is this possible with non-parametric statistics?
Thank you</p> | g68150 | [
0.016342194750905037,
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0.009416060522198677,
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-0.04113279655575752,
0.005025864578783512,
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0.019347848370671272,
... |
<p>A quick look at the <a href="http://stat.ethz.ch/R-manual/R-patched/library/base/html/Random.html" rel="nofollow">help page</a> of the random number generator of R shows that you can choose among 7 predefined generators (<code>Wichmann-Hill</code>, <code>Marsaglia-Multicarry</code>, <code>Super-Duper</code>, <code>M... | g28029 | [
-0.011904837563633919,
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0.... |
<p>Suppose one is interested in stochastic processes for the purpose getting a theoretical understanding of MCMC. They already have a decent understanding of probability theory (let's say at the level Billingsley) and want to develop enough tools to potentially prove theorems about the Markov Chains they construct at a... | g68151 | [
0.03235211595892906,
0.047525741159915924,
0.019734647125005722,
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0.008956287056207657,
0.0302302036434412,
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0.030794555321335793,
0.024328917264938354,
0.0020362155046314,
0.06005318462848663,
-0.0091447... |
<p>I am modelling a nested mixed-effects model with just the intercept in the random part, of the form:</p>
<pre><code>fit4<-lme(fixed = Stdquad~factor(LayoutN)+factor(nCHIPS.fixed), random = ~1|Class.Ordered/student)
</code></pre>
<p>When trying to check the assumption on the independent, identically distributed ... | g47316 | [
-0.03271808847784996,
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-0.024155491963028908,
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-0.0598326250910759,
0.008224064484238625,
0.03484516590833664,
0.006589369848370552,
0... |
<p>I'm trying to determine a good model to use to predict multivariate count data given a row of multivariate normal as inputs.</p>
<ul>
<li>The training set is $N\times D$ and the response set is $N\times P$, where $N$ is the number of observations and {$D,P$} are the number of features in the training and response r... | g28031 | [
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0.033884309232234955,
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0.04859958961606026,
-0.0... |
<p>In large sample theory, I'm told that as $n$ grows larger and larger ($n$ being the number of samples in a dataset) that $\sqrt n(\hat \beta_1-\beta_1)$ gets closer and closer to normal distribution. What exactly is $\sqrt n(\hat \beta_1-\beta_1)$?</p> | g68152 | [
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0.03725982829928398,
0.021831445395946503,
-0.00... |
<p>how can I find the marginalized "messages" $m(x_0)$... $m(x_n)$ ($x_1$ as example)
$$m(x_1) = \int{ P(x_0|x_1,x_2,...) P(x_0)P(x_2)... dx_0 dx_1}$$
where $P(x_0|x_1,x_2,...) \sim N(m_0+x1+x2;v_0)$ </p>
<p>and $P(x_1) \sim N(m_1;v_1)$, $P(x_2) \sim N(m_2;v_2)$, ... ?</p>
<p>So I have the product of a normal dist... | g37535 | [
0.03286222741007805,
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0.003086251439526677,
0.02478114888072014,
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0.... |
<p>My time series is <a href="https://dl.dropboxusercontent.com/u/13029929/TS/ts.txt" rel="nofollow">here</a> and my code is <a href="https://dl.dropboxusercontent.com/u/13029929/TS/code.r" rel="nofollow">here</a>.</p>
<p>I fit a model to a series with <code>arima()</code> in R with ARMA(5,5) and regression on some co... | g68153 | [
0.016714926809072495,
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0.0400528758764267,
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0.05056709796190262,
-0.028058... |
<p>I am attempting to perform regression calibration on some test data to familiarize myself with the idea behind it. I don't have much of a stats background. The method rcal in Stata seems to be what I am looking for, however I am having trouble when trying to regress on only one variable.</p>
<p>In the following exa... | g68154 | [
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0.03386464715003967,
0.006414155010133982,
0.017382586374878883,
0.026... |
<p>I measured prey capturing success (=proportion of successful captures divided by the total number of prey captured) in four fish species (species 1: n=19, species 2: n=18, species 3: n=4, species 4: n=3) and would like to compare the prey capturing success between the four species. However, as there might be an indi... | g68155 | [
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0.021258212625980377,
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0.021060841158032417... |
<p>Related Question: <a href="http://stats.stackexchange.com/questions/7257/learning-weights-in-a-boltzmann-machine">Learning weights in a Boltzmann Machine</a></p>
<p>I'm trying to understand RBMs and how they are applied in training of Deep Architecture. Being new to the field of statistics, I stumbled upon various ... | g68156 | [
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0.10318800806999207,
0.03705540671944618,
0.00709... |
<p>I'm working with a uniform distribution as a prior, defined as:</p>
<p>$\pi(\theta) =
\begin{cases}
\frac{1}{7} & \text{if } \theta\in\{0,\frac{1}{6},\frac{2}{6},\ldots,1\} \\
0 & \text{otherwise }
\end{cases}$</p>
<p>I've to compute the prior predictive, but I don't know how to deal with t... | g68157 | [
0.0625801756978035,
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0.01011535245925188,
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0.02285090833902359,
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<p>I am trying to understand the difference between iid and non-iid data.</p>
<p>Let's consider a given time series, and say it's reasonable to assume that at each time point the random variable $X_t$ depends on $X_{t-1}$. </p>
<p>Now say someone gives me the dataset $ D = \{ ( t_i, x_i ) \} $ for $i=1 \dots n$. I mi... | g68158 | [
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0.022166399285197258,
0.040237873792648315,
0.014330608770251274,
... |
<p>I am trying to put a number to the distance of a sequence and how close it is to the original training corpus. </p>
<p>From the original training data, I got a markov transition matrix (TM). </p>
<p>So from the sequence I am trying to evaluate, I have all the transition probabilities. </p>
<p>I could calculate a ... | g68159 | [
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0.0049437847919762135,
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0.03946131467819214,
0.08666335046291351,
-0.00... |
<p>Hi all and thank you in advance for helping!</p>
<p>I have three variables: $y$ the dependent count variable, $x$ the independent positive continuous variable, $U$ is the observation unit (and I expect a random effect with it). I would like to test the hypothesis that the slope for $x$ is positive. I would normally... | g28036 | [
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... |
<p>I am trying to get related documents for a list of 10,000 documents from the same set of 10,000 docs. I am using two algorithms for testing: gensim lsi and gensim similarity. Both give terrible results. How can I improve it?</p>
<pre><code>from gensim import corpora, models, similarities
from nltk.corpus import sto... | g68160 | [
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0.05696795508265495,
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0.023717302829027176,
0.025285106152296066... |
<p>I was doing machine learning course at coursera and there was a lecture about diagnosing high bias, or high variance from learning curves. If anyone interested here is the lecture - <a href="https://class.coursera.org/ml-003/lecture/64" rel="nofollow">https://class.coursera.org/ml-003/lecture/64</a>. I just can't fi... | g28037 | [
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0.05619063600897789,
0.04550565406680107,
0.08910217881202698,
0.026... |
<p>If x and y are uncorrelated normal variates, x*exp(y) will have a symmetric unimodal distribution with positive excess kurtosis. Has this distribution been named and studied?</p> | g28038 | [
0.018686488270759583,
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0.01757967099547386,
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0.011164037510752678,
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... |
<p>I have a distribution of microparticles that follows a lognormal distribution. The cumulative distribution function thus is given by:</p>
<p>$$
F_X(x;\mu,\sigma) = \frac12 \operatorname{erfc}\!\left(-\frac{\ln x - \mu}{\sigma\sqrt{2}}\right)
$$
$$
\mu = ln(M) + \sigma^2
$$</p>
<p>Now, the plot of the distribution ... | g28039 | [
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0.005855842959135771,
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0.04792120307683945,
0.00562408147379756,
-0... |
<p>The source in question is some blackbox which output looks completely random to me, yey I haven't tested if for randomness quality. I don't exactly know insides of blackbox but can easily caputure it output 160bit integers, millions if necessary. </p> | g68161 | [
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0.05530523508787155,
0.01078876294195652,
-0.... |
<p>I have run a classical Poisson regression model and a Poisson random effect model in R. I want to know if there is any goodness of fit for the Poisson random effect model?</p> | g28041 | [
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0.01058109849691391,
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... |
<p>I am a dummy in statistics but need to accomplish some simple survey analyses.
My question is: if I have several questions (items) for one construct (say, questions JS1-JS3 for job satisfaction) with the same 5-point scale, how do I do descriptive stats for the construct?</p>
<p>Is it ok to calculate the mean &... | g28042 | [
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<p>I've been mulling over a problem that has something like the following form. I don't have a math or stats background so advice and answers at various levels, from terminological to strategic, would be helpful. I'll start off with the example that I've been thinking about and then move on to the specific case I'm wor... | g68162 | [
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-... |
<p>I would like to fit a piecewise linear regression with knots as parameters. I would like to know what's the best solution.</p>
<ul>
<li>Should I run a set of regressions with all the possible knots and choosing the knots which could minimize an information criterion such as AIC (Akaike Information Criterion)? </li... | g28044 | [
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<p>How can one use nested cross validation for <strong>model selection</strong>? </p>
<p>From what I read online, nested CV works as follows:</p>
<ul>
<li>There is the inner CV loop, where we may conduct a grid search (e.g. running K-fold for every available model, e.g. combination of hyperparameters/features)</li>
<... | g68163 | [
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<p>I am trying to compare correlations between subgroups of a variable. For instance, I am trying to compare the income of group 1 v. income of group 2 v. income of group 3 v. income of group 4, where the groups are specified by another categorical variable. </p>
<p>What I did was create new variables separating out t... | g68164 | [
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<p>I need to use an LPM for a paper I'm doing (for reasons orthogonal to this question). I have about 6000 observations in a time series cross-sectional structure (countries and years) and my dependent variable is binary. </p>
<p>Now, I know all the standard arguments against the LPM, but I am wondering whether the c... | g28047 | [
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<p>I have a corpus of many short entries. Because of this it is very rare that for two entries $x_i, x_j: \ <x_i,x_j> \neq 0$. Therefore for almost all the entries, $x\in TeS$, in the test set I get $\forall x_i\in TrS, \ <x,x_i>=0 $ where $TrS$ is the training set. Therefore SVM is unable to classify most... | g68165 | [
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<p>Although my question sounds like I have data suitable for log-linear analysis, I may not. I have a large number of students (about 1000) of two levels who solved a test of 8 different types of problems (which have specific features and categorized at two different levels). </p>
<p>Thus I have three types of indepen... | g343 | [
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<p>Suppose we are want to consider the asset price $P_t$ (business daily) of some stock. The log return is defined as</p>
<p>$$X_t:=\log{\frac{P_t}{P_{t-1}}}$$</p>
<p>suppose we are considering the prices between some interval, eg. June 1986 and March 1990). Log returns can be modelled by $X_t=\sigma_t\epsilon_t$, wi... | g68166 | [
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<p>Are there implemented tests in R to check heteroscedasticity and linearity for multilevel regressions? I am using a two Level Regression Framework (lmer function in R).
Is it necessary to do those tests if i use a MCMC Approach (MCMCglmm in R)? How do i perform those test when using MCMC to estimate multilevel regr... | g28050 | [
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<p>Can someone please explain to me why the covariance matrix needs to be positive definite for the Hausman test? And why we can skip this restriction by applying the "test of overidentifying restrictions"?</p>
<p>Isn't the issue easily explainable when simply comparing the formula of the Hausman test statistic and th... | g68167 | [
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<p>I am trying to replicate an analysis as conducted by Raven, et al. (1998). A scale is analyzed with Guttman's smallest space analysis. First of all I wasn't able to find a suitable procedure in R and it appeared to me as if SPSS might be the solution. However even though I use the same scale it is impossible to repr... | g68168 | [
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<p>I'm working on a project to estimate real estate and started with some classique techniques, such as linear regression etc. The obtained results are already going in the good direction, but to get some more precise results, I've started to lookup some more advanced models.</p>
<p>First I've looked into a spatial au... | g68169 | [
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<p>Assume that the sample $X_i, i=1,\dots, n$, is iid normally distributed with unknown mean and variance $\theta = (\mu, \sigma^2)$. The Wald test statistic of testing if $\mu = \mu_0$ is
$$W=\frac{n(\hat{\mu} - \mu_0)^2}{\hat{\sigma}^2}$$
where $\hat{\sigma}^2 = \frac{\sum_i (X_i - \hat{\mu})^2}{n}$ is the maximum-... | g68170 | [
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<p>I ran a confirmatory factor analysis in Stata using the <code>sem</code> command. The idea was to extract two factors: TRUST, extracted from four variables measuring the trust towards different groups of people (friends, strangers etc.) on a scale from 1 to 7; SELF-RELIANCE, extracted from four variables measuring t... | g28054 | [
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<p>I can't figure out the meaning of emphasized phrase in the following:</p>
<blockquote>
<p>Representing a <em>grouped error distribution</em> by a multinomial distribution, Simpson (1756), Langrange (1776), and Laplace (1776) used the classical methods for deriving the distribution of the mean rectangularly and tr... | g68171 | [
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<p>I want to see if there is a significant relationship between the mating (response variable) and several explanatory variables such as individual number (categorical), leg movement (continuous) and the reuse of individuals (categorical). My data looks like this: </p>
<pre><code>Mating ID Replication Shaking
1 ... | g28055 | [
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... |
<p>I have two data sets. The first data set, let's call it $X$ has an average value of $\bar{x}_{X}$ and standard deviation of $s_{X}$, the second data set $Y$ has an average value of $\bar{x}_{Y}$ and standard deviation of $s_{Y}$.I want to find out the standard error or standard deviation of a percentage change of da... | g49796 | [
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<p>I'm trying to model 10 years of monthly time series data that is very choppy, and overall it has an upward trend. At first glance it looks like a strong seasonal series, however the test results indicate that it is definitely not seasonal. This is a pricing variable that I'm trying to model as a function of macroeco... | g68172 | [
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<p>I have data on content-based recommendations of movies and their attributes. </p>
<p>Suppose a user likes x,y and z and also dislikes c and d movies. I want to predict movies that he will like based on his likes and dislikes.</p>
<p>It is actually quite easy to find similar items if the only interaction were a mov... | g68173 | [
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<p>What is the validity of using a <em>kernel-density-estimation</em> to <em>compare model x observed data</em>?</p>
<p>In other words, if the <em>KDE</em> curve for the observed data looks like the <em>KDE</em> for the model forecast, can I use this result as a quality measure for the model? If not, why?</p>
<p>In t... | g5456 | [
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<p>I am using Artificial Neural Networks (FFBP, RBF, GRN) and Multi Linear Regression techniques to model a real world case study.</p>
<p>I have a small list of records (60 data items).
I am using 48 of 60 as my training data set and the remaining 12 as my testing data set.</p>
<p>I have two diagrams: one is based o... | g68174 | [
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<p>I've built a little naive Bayesian classifier that works with Boolean and real values. Boolean distributions are dealt with via Bernoulli distributions, while real valued data are dealt with kernel mixture estimators. I'm currently in the process of adding count data in.</p>
<p>How would one deal with categorical d... | g68175 | [
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<p>I used a stepwise multiple regression to generate a model and I am trying to appropriately report the results by indicating the (additional) variance explained by each included factor. I'm not sure how to extract that information, however.</p>
<p>Basically my code thus far is simply:</p>
<pre><code>init <- lm(d... | g48893 | [
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... |
<p>Suppose $X_1,\ldots,X_n$ are i.i.d. $\mathcal U(0,1)$. I am looking for the asymptotic distribution of $$T_n = \prod_{i=1}^n [e{X_i}]^{1/\sqrt{n}} \>.$$</p> | g48894 | [
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0... |
<p>Initially we have this regression:</p>
<p>$$
\text{hourly wage} = 12.69 + 5.44\text{CollegeEducation} - 2.64\text{Female}
$$</p>
<p>with standard errors of $0.21$ on $\text{CollegeEducation}$ and $0.20$ on $\text{Female}$. The variable $\text{Age}$ is added to the regression, which has a coefficient $0.29$, but th... | g68176 | [
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<p>I have a couple of user profiles, that contain hashtags like this:</p>
<p>user1: #sports, #bike, #enduro, #racing, #mountainbike
user2: #sports, #bike, #racing, #mountainbike, #mtb
(...)
userN: #mtb</p>
<p>I would need to find an algorithm, that constantly builds up correlating word groups out of all the hashtags ... | g68177 | [
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0.011443226598203182... |
<p>I wanted to run a quick and easy (or so I thought) regression on some data I have but now I am starting to doubt whether or not the regression makes any sense. I have seen some similar questions but they don't really answer what I want to know.</p>
<p>I want to run an ordered probit/logit with the dependent variabl... | g68178 | [
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0.009... |
<p>Many clustering algorithms can be used with big data, eg. versions of KMeans, DBSCAN based on Hadoop, etc. But, with k means we will get k centroids for k clusters and we can map them to the space and somehow understand the results. But what about density based algorithms like DBSCAN? In DBSCAN we'll get m clusters ... | g68179 | [
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0.00939... |
<p>I have data to fit a one-way ANOVA model to categorical data. I used a simple model first, getting significant coefficients, but with an $R^2$ of 0.2.</p>
<p>I then tried a log model and got more significant coefficients, but the $R^2$ is still only 0.3.</p>
<p>Is this normal for categorical data? Are there any ot... | g68180 | [
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<p>I have a class with 52 students. Every student has a grade. I want to know how many of the student grade in compaire with a special number(for example 15) is statically significant? </p> | g68181 | [
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... |
<p>I'm trying to analyze if there are correlations between binomial dataset. I have binomial data (presence/absence) of two variables in different periods and I need to know what is the best way to find some relationship. Data were taken annually from the same samples.</p> | g68182 | [
0.046792399138212204,
-0.08631380647420883,
0.023765455931425095,
-0.011266578920185566,
-0.031307678669691086,
0.0141834681853652,
0.039200715720653534,
-0.016053564846515656,
0.005456197075545788,
-0.0351838544011116,
0.0328153520822525,
-0.01003266405314207,
-0.0020910827443003654,
0.01... |
<p>Imagine a simple set up where where entities (e.g. a restaurant) are rated every year with 5 rating categories $c_t$: <em>excellent</em>, <em>good</em>, <em>medium</em>, <em>poor</em> and <em>bad</em>. </p>
<p>Now assume that I have some underlying data $X^i_t=(x^{1i}_t,x^{2i}_t, ..., x^{pi}_t)$ at entity level $i$... | g28066 | [
-0.028802139684557915,
0.02630266174674034,
0.001815887982957065,
-0.05411756411194801,
-0.0037106340751051903,
-0.04038030281662941,
-0.008909006603062153,
0.017099646851420403,
-0.04080305993556976,
-0.009828366339206696,
0.020702874287962914,
0.039846792817115784,
0.03492886573076248,
-... |
<p>When is it appropriate to use a backward method in regression? I have read that it is permitted for exploratory model-building, but I have also read negative things about it. </p>
<p>I am making a model about streaming. The 12 predictors I chose are based on theory. The enter method is not an option, because when I... | g28067 | [
-0.009713126346468925,
0.03751577436923981,
0.02099977247416973,
-0.013082641176879406,
0.003052658401429653,
-0.016921157017350197,
0.009921572171151638,
0.05528293550014496,
-0.06477732956409454,
-0.049921777099370956,
0.01429955568164587,
0.03876651078462601,
0.039807576686143875,
0.073... |
<p>I have one dependent variable <code>C</code> and four independent variables: </p>
<ul>
<li><code>S</code></li>
<li><code>SD</code></li>
<li><code>TPA</code></li>
<li><code>VPT</code></li>
</ul>
<p>The correlation matrix between them is the following</p>
<pre><code> TPA VPT S
TPA - - -
VPT ... | g68183 | [
0.012069543823599815,
-0.04412950575351715,
-0.029189180582761765,
-0.04782523214817047,
0.04332539066672325,
0.04678962379693985,
-0.02318746969103813,
0.028766976669430733,
-0.034398067742586136,
-0.03955187648534775,
0.015136152505874634,
0.028978310525417328,
-0.0035049922298640013,
0.... |
<p>I have a question about different strategies for randomly picking up a reference set for statistical testing from a large amount of data (and permuting over the random picking/testing). </p>
<p>For illustration purposes, we could assume that the data is e.g. time series data (could be something else as well), where... | g68184 | [
0.019676193594932556,
0.02902953140437603,
-0.010059121996164322,
-0.02446269802749157,
-0.05690189078450203,
-0.025872182101011276,
0.024470653384923935,
-0.014314178377389908,
-0.013383102603256702,
0.012408286333084106,
0.026895269751548767,
0.0017679283628240228,
0.028972920030355453,
... |
<p>I found two different definitions of <a href="http://en.wikipedia.org/wiki/Neyman%E2%80%93Pearson_lemma" rel="nofollow">Neyman-Person lemma</a>, one using the size $ \alpha $ and one the level $ \alpha $ of a test.
I know the two concepts are related, but not synonymous.</p>
<p>Is the lemma the same in both cases? ... | g68185 | [
0.029170891270041466,
0.002231173450127244,
0.00817448366433382,
-0.06590080261230469,
-0.007818801328539848,
-0.00013895414303988218,
0.04761910438537598,
0.010511654429137707,
-0.01393816713243723,
0.013368291780352592,
-0.012296375818550587,
-0.03612647205591202,
0.006569837220013142,
0... |
<p>I'm doing principal component analysis on my dataset and my professor told me that I should normalize the data before doing the analysis. My question is: "Why?" :) </p>
<p>What would happen If I did PCA without normalization? Why do we normalize data in general? Could someone give clear and intuitive example which ... | g49660 | [
0.057202573865652084,
-0.02810528688132763,
0.029675759375095367,
-0.025159446522593498,
-0.021837403997778893,
0.0067052231170237064,
0.04570244252681732,
0.06843067705631256,
-0.04456638544797897,
-0.0351850688457489,
0.0241289921104908,
0.04031016305088997,
-0.01654125191271305,
0.00648... |
<p>I want to estimate the parameter $\mu$ using the difference between two Poisson distributions with the same parameter, i.e. a <a href="http://en.wikipedia.org/wiki/Skellam_distribution" rel="nofollow">Skellam</a> distribution with $\mu_1=\mu_2 = \mu$. </p>
<p>I can calculate the variance of the Skellam distributio... | g68186 | [
0.037887126207351685,
-0.041806384921073914,
-0.0022761879954487085,
-0.007672416511923075,
0.002541144145652652,
-0.047644369304180145,
-0.03446488827466965,
-0.01052479911595583,
-0.06514670699834824,
0.0046892790123820305,
-0.02215866930782795,
-0.007247272878885269,
-0.010629206895828247... |
<p>Edit: I think the data was poorly given, varables coke, pepsi, and sprite were just given in 2 columns when I got it, but it has nothing to do with before and after treatment?</p>
<p>here's the original questions since someone asked
For the study, 2 males and 2 females are picked randomly from NYC, and a random sam... | g28074 | [
-0.02613270841538906,
-0.06265188753604889,
-0.00704014440998435,
-0.05163303390145302,
-0.0090159447863698,
-0.01806539110839367,
0.048024982213974,
-0.002678425284102559,
-0.04152790084481239,
0.03511021286249161,
0.03230168670415878,
0.023121913895010948,
0.04075576737523079,
-0.0189579... |
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