question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I’ve noticed that in R, Poisson and negative binomial (NB) regressions always seem to fit the same coefficients for categorical, but not continuous, predictors. </p>
<p>For example, here's a regression with a categorical predictor:</p>
<pre><code>data(warpbreaks)
library(MASS)
rs1 = glm(breaks ~ tension, data=war... | g63897 | [
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<p>I want to apply a GAMM with R to this time series but I am not sure how to handle the station P18, as shown in the figure below.</p>
<p><img src="http://i.stack.imgur.com/4uSak.png" alt="enter image description here"></p>
<p>If I shrink the dataset to the point where P18 ends (i.e. left side of the dashed line) I ... | g63898 | [
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<p>I have <a href="http://en.wikipedia.org/wiki/Case_fatality_rate" rel="nofollow">case fatality rates</a> (deaths per 100 cases) for 2 different states receiving different treatments for 17 years.</p>
<p>What is the best statistical method to compare them? Relative risk, odds ratio, plain time series analysis, ...?</... | g63899 | [
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<p>I am using the ar() function to fit an AR model to some data, and this object will return the in sample residuals. I also know the syntax for how to get the corresponding predicted values, but I want to compute these predicted values manually (just to check my own understanding) for a simple AR(1) example. </p>
<p>... | g305 | [
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<p>I am using a mixed repeated measures with an ARMA(1,1) variance covariance structure. I have a basic understanding of why I am using this model etc but I need some help on articulating a few things:</p>
<ol>
<li><p>How does this model correct for the variance in time between each time point? Or does it ignore the p... | g63900 | [
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<p>I am always struggling with normality testing for quantitative predictors (no factors) and transforming them to normality. </p>
<ul>
<li>If I am running a GLMM and my predictors are really non-normal, should I transform them as well to try to make them normally distributed? </li>
<li>I know that this is important ... | g49518 | [
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<p>Let X and Y be two random variables with means $μ_X$ and $μ_Y$ , variances $σ^2_Y$, $σ^2_X$ and covariance $σ_{XY}$ . Show that $E(XY) = σ_{XY} + μ_Xμ_Y$?</p>
<p>I tried the Covariance formula with:</p>
<p>$$Cov(X,Y) = E(X − E(X))(Y − E(Y ))$$
$$\int_{-\infty}^{\infty}{(x − E(X))(y − E(Y ))f(x, y)dxdy}=$$
$$=E(XY ... | g63901 | [
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<p>I have count data for a number of subjects in different groups I would like to compare. The averages of the cumulative sums are shown in the figure below. As you can see the Red group has a spike at the end. This is because one subject in that group had fewer trials. This subject had the lowest cumulative number of ... | g63902 | [
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<p>I wish to find the parameter $\nu>2$ for the student t-distribution such that the following constraint will hold: if $F_T$ is the CDF of that distribution and $F_N$ is the CDF of the normal distribution, then
$$\frac{F_T\left(-2\sqrt{\frac{\nu}{\nu-2}}\right)}{F_N(-2)}=c$$
for some pre-determined $c$.</p>
<p>The... | g63903 | [
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<p>I have a doubt regarding the variance, I try to explain It with an example.</p>
<p>I have two vectors, like:</p>
<pre><code>a <- c(1:10)
1 2 3 4 5 6 7 8 9 10
b <- c(10:1)
10 9 8 7 6 5 4 3 2 1
</code></pre>
<p>the variance is obviouly the same:</p>
<pre><code>> var(a)
9.166667
> var(... | g63904 | [
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<p>I use 48 energy functions to score protein-ligand interactions. I have a dataset of protein-ligands for which I know the experimental binding energy, so I can compare it with the score assigned from each energy function. With those data I can do step-wise multiple regression to find a linear combination of the follo... | g63905 | [
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<p>I am calculating this example at the moment. Are my calculations right?</p>
<p>The random variable $Y$ has a mean of 15 and a variance of 9. $Z =
1/3 (Y − 15)$. Show that $Z$ has variance $1$.</p>
<p>$Z = \frac13 (Y − 15)$
$, \newcommand{\stdev}{\mathrm{stdev}}\stdev(Y)=3$</p>
<p>$$\stdev(Z)=\frac13 (Y − 15) = \... | g37682 | [
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<p>I am applying a MAP log-likelihood approach in order to fit a Markov mixture model, where objective function to be maximized is given by the formula:</p>
<p>$$
L(X|\Theta _K)=\sum_{i=1}^{n}f(X_i|\Theta_K)+\sum_{j=1}^{K}\sum_{n=0}^{M}\log p(\theta_n^{j}|a_n^{j})
$$</p>
<p>where the second argument is a sum of Diric... | g63906 | [
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<p>Suppose we have case-control data, where cases have some disease ($Y$) and controls don't and we are interested in the association of some other variable(s) ($X$). I know that in this scenario we cannot use the disease as the response variable because of the experimental design (the marginal distribution of disease ... | g21792 | [
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<p>I am attempting to use <code>MuMIn</code> to run a model selection analysis on a mixed model fitted using <code>lme4</code>. </p>
<p>Because this model is fit using restricted maximum likelihood (REML), I am confused as to whether I can use an automated model selection approach such as that implemented in <code>Mu... | g63907 | [
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<p>Goldman Sachs decided to apply their brains to predicting the winner of the World Soccer cup. They built a statistical model analyzing past winners. </p>
<p>I read about it <a href="http://www.washingtonpost.com/blogs/wonkblog/wp/2014/05/28/can-goldmans-economists-predict-who-will-win-the-world-cup/" rel="nofollow"... | g21793 | [
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<p>A user interacts with X number of features before they go on to convert. How do I determine which features, <strong>and in what order</strong>, is the most common path to conversion? </p>
<p>For example, if I was doing this analysis for Amazon I would have a "viewed product page" feature and an "add to wishlist" ... | g11266 | [
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<p>Suppose that my prior estimate for the bias of a coin is split evenly between a beta distribution (Theta,20,10) and a beta distribution (Theta,20,20), with Theta indicating the probability of tossing heads. Hence my prior is 0.5*Beta(20,10)+0.5*Beta(20,20). Assume that i observe that among 30 coin tosses i get 20 he... | g63908 | [
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<p>Note: Case is n>>p</p>
<p>I am reading Elements of Statistical Learning and there are various mentions about the "right" way to do cross validation( e.g. page 60, page 245). Specifically, my question is how to evaluate the final model (without a separate test set) using k-fold CV or bootstrapping when there has bee... | g63909 | [
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<p>I am trying to reproduce the anova table for a 2x2 cross-over design. I used the data listed in tables 2.1 and 2.2 of the "Design and Analysis of cross-over trials" book, by Jones and Kenward. I am giving all the code so that you can reproduce the calculations. </p>
<pre><code>g1AB <- read.table(textConnecti... | g41223 | [
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<p>Assuming the following model (Fir instant, received signal of a communication / RADAR system):</p>
<p>$$ x[n] = \alpha s[n] + w[n] $$</p>
<p>Where:</p>
<ul>
<li>$ s[n] $ is a known signal of length $ L $ and known energy $ p = \sum_{n=0}^{L-1} {s}^{2}[n] $.</li>
<li>$ \alpha $ is unknown attenuation factor. Thoug... | g15787 | [
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<p>I found this book "Statistical methods in atmospheric sciences" by Daniel Wilks in the library. Do you think it is good for learning statistical methods in general?
The examples are as you might know or expect, from atmospheric sciences but discussion about the statistical methods is quite good. </p> | g63910 | [
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<p>Okay, I'm aware of the fact that Gosset came up with <em>t</em> distribution, but what is the etymology of "t". How did "t" end up in t-test and t distribution?</p> | g41225 | [
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<p>I have preformed multiple tests and now have a list of all the calculated P-Values (~30K^2 values). I have a reason to believe my tests are somehow dependent.</p>
<p>I would like to analyze the results and correct the p-values.</p>
<p>Unfortunately, I only have very basic knowledge in statistics. From the little I... | g63911 | [
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<p>Having a map such as:<br>
<img src="http://i.stack.imgur.com/0NLWV.png" alt="enter image description here"><br>
<strong>How to find major directions of variation</strong> i.e., for the example given here: north-east--south-west? in an elegant, quick and clean way?
Any ideas are more than welcome.</p> | g63912 | [
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<p>I've been given a set of 20 Likert-items (ranging from 1-5, sample size n = 299) within the field of organizational research. The items are intended to measure a latent concept which is multidimensional, multifaceted and heterogenous in it's very nature. The goal is to create a scale(s) which can be nicely used to a... | g63913 | [
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<p>I have a light curve, that is photon count rate versus time, of an astronomical object. These data are periodic, since the source signal is periodic. I can fold the data with the period and obtain an average profile.</p>
<p>At this point, I want to check whether the single profiles are statistically different from ... | g138 | [
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<p>How does one tell if a dataset is missing data at random? I've been reading up on how to impute missing values, and was wondering what techniques can be used to tell if data is really missing at random or systematically.</p> | g63914 | [
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<p>I have a simple model without interaction and it stated significant effect for all the explanatory variables (continuous variable rok and categorical variables obdobi (levels hn and nehn) and kraj:</p>
<pre><code>Call:
glm(formula = cbind(ml, ad) ~ rok + obdobi + kraj, family = "quasibinomial")
Deviance Residuals:... | g63915 | [
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<p>I am analysing the effect of density (categorical), gonad mass (continuous) and temperature (continuous) on the percentage of acini spawning in a gonad. My replicate unit is a scallop.</p>
<p>As my response variable is a percentage, and I have many zeros, I was wondering if a zero inflated Poisson regression would ... | g63916 | [
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0.0058230385184288025,
0.025949079543352127,
... |
<p>when I used LDA model in my project, the result topic terms vary with the random seed. how to solve this problem ? thanks</p> | g4421 | [
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<p>For my PhD dissertation, I am offering a conceptual model on teacher professional development. My model has one mediator. I wonder if I can test the mediation through Baron and Kenny's procedure or bootstrap and then conduct structural equation modeling (SEM) analysis. Many say the first step (testing mediation) is ... | g63917 | [
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<p>Has anyone worked with semi parametric methods to estimate parameters with binary outcome? Examples are like Cosslett (1983) or Ichimura or Klein-Spady. In other words we are looking for semi parametric methods instead of probit/logit.</p>
<p>I was wondering if anyone has written R code or Matlab code in this regar... | g63918 | [
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<p>I have two methods which are being used to estimate a specific signal. I have a ground truth measurement of this signal and these two methods are using noisy data to estimate this signal. This signal is computed using a sliding window, meaning that two consecutive estimates are not independent (the window is 30 seco... | g63919 | [
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<p>I have ran this model in R:</p>
<pre><code>model <- lm(mpg ~ hp + drat + disp, data=mtcars)
</code></pre>
<p>And I have visualised this model using <code>effects</code> package in <code>R</code>:</p>
<pre><code>library(effects)
model_effects <- effect("hp", model, list(drat=mean(mtcars$drat), disp = mean(mt... | g63920 | [
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0.00... |
<p>For $J$ units of observations my basic model contains latent variables $\theta_j, j = 1, ..., J$ identified by the marginal assumption
$\theta \sim N(0,1)$. The latent variables are connected to a vector of observed binary variables $(x_{j1},...,x_{jI})$ via a binomial model and the logistic link:</p>
<p>$logit(P(... | g63921 | [
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0.03553174436092377,
... |
<p>I am running regression analyses in matlab with glmfit and calculate significance of contrasts of parameter estimates by using standard errors. Somehow however, the results I get are not consistent with SPSS results, so I'm wondering if I am doing something wrong.</p>
<p>Hence 2 Questions:</p>
<ol>
<li>Can somebod... | g63922 | [
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0.02863... |
<p>I'm working through a stats textbook and have a question of the form:</p>
<blockquote>
<p>You will perform a significance test of $H_0: μ=25$ based on an SRS of $n=25$. Assume $σ=5$.</p>
</blockquote>
<p>I'm stuck on the 'equals' part of $μ=25$. Given that we're working in the set of reals, isn't the probability... | g21809 | [
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<p>I've recently run into an issue where I am trying to test for a statistical difference between two groups, where each element of a group is itself a data object. For any pair of objects, I can calculate a similarity score. I want to check if the groups of objects are statistically different based on those similari... | g63923 | [
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<p>I have an experiment with 3 equal group sizes and 4 measures. I think the simple null hypothesis is that the three groups will be the same. Most people, however, believe that group A should do best in measure 1, group B should do best in measure 2, group 3 should do best in measure C, and they should all be the same... | g63924 | [
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<p>Does somebody have an idea to find the following expectation:</p>
<p>$$E(X\log(a+bX)),$$
How can I proceed, can we go like this:</p>
<p>$$=E(X)E[\log(a+bX)],$$if yes then what?</p> | g38730 | [
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<p>Trying to perform a Bayesian ordered logistic regression in R where age is my outcome variable. I have installed the ARM package but I am unsure how to go about generating my model in R. I also need to perform an ordered logistic in R using a Frequentist approach and use my model to generate predictive probabilities... | g21812 | [
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0.031... |
<p>I know that one of the advantages of mixed models is that they allow to specify variance-covariance matrix for the data (compound symmetry, autoregressive, unstructured, etc.) However, <code>lmer</code> function in R does not allow for easy specification of this matrix. Does anyone know what structure <code>lmer</co... | g63925 | [
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0.01897730492055416,
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0.00... |
<p>I have a question about <code>plm</code> package. </p>
<p>My code is:</p>
<pre><code>fixedmodel <- plm(formula=Inv_ret~Firm.size+leverage+Risk+Liquidity+Equity,
data=datanewp, model="within")
</code></pre>
<p>In the <code>plm vignette</code> the authors write: </p>
<blockquote>
<p>This is ... | g63926 | [
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0.09215611964464188,
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... |
<p>Analyzing educational datasets we have samples of children from samples of class in samples of schools - we have sampling weights, so I use the survey package e.g. to do a linear model. But this kind of design also requires looking at the mixed effects. But this isn’t possible using the survey package. I can do this... | g63927 | [
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0.04... |
<p>A simulation gives the population numbers for every species in the domain per frame. These vary over time and can be quite noisy, is there a way of analysing the data algorithmically without drawing a graph whether or not these values oscillate?</p> | g45306 | [
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<p>I'm having a problem to predict hits from original features. I tried using LDA on original matrix but the thing is that probability of getting a hit vs non-hit is 95% vs 5%. That said after running LDA I get true positive rate of 5% and true negative rate of 96%. Now, my understanding of LDA makes me think that when... | g63928 | [
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0.0... |
<p>I'm really new to statistics so sorry in advance if this question does not make sense.</p>
<p><strong>Background:</strong></p>
<p>I'm trying to learn about hidden Markov models and they seem interesting but I was wondering about the probabilities they use to generate their predictions. Most of the information I ha... | g63929 | [
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... |
<p>What is the cleanest, easiest way to explain someone the concept of variance? What does it intuitively mean? If one is to explain this to their mom or child how would one go about it?</p>
<p>It's a concept that I have difficulty in articulating - especially when relating variance to risk. I understand it mathematic... | g63930 | [
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<p>Is there an easy/standard way of sampling from a density estimated by kNN? I've searched online but I can't seem to find how to do this. Any links or methods pointing me in the right direction would be much appreciated. Just to clarify, I would want to be able to sample points not (necessarily) in my dataset from th... | g21818 | [
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<p>In time series analyses, I have used multi-level or random/mixed effects to deal with auto-correlation issues (i.e., observations are clustered within individuals over time) and added controls are added for some specification of time and for shocks of interest. ARMA/ARIMA seem designed to address similar issues.</p>... | g63931 | [
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<p>I would like to employ count data as covariates while fitting a logistic
regression model. My question is:</p>
<ul>
<li><strong>Do I violate any assumption of the logistic (and, more in general, of the
generalized linear) models by employing count, non-negative integer
variables as independent variables?</strong></... | g11271 | [
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<p>Does the order of the items in a questionnaire matter? If so, how do I know which item should go first, second, third etc. when devising a questionnaire? </p>
<p>Thanks</p> | g63932 | [
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-0.... |
<p>I have a $n \times p$ matrix $A$ where $n$ is the number of observables and $p$ is the number of observations. $n \gg p$ </p>
<p>In my code, I have done $[E,V] \,=\, eig(A)$ and doing a least squares operation on the eigenvector matrix $V$, which is $p \times p$. This is using the <code>mldivide</code> operator in ... | g63933 | [
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0.0442560538649559,
0.0798... |
<p>We consider the following GARCH(1, 1) model:</p>
<p>$y_t = h_t \epsilon_t$ where $(\epsilon_t)_{t \in \{1, \dots, n\}}$ are i.i.d. random variables with mean 0 and standard deviation 1. </p>
<p>$h_t = \omega + \alpha \epsilon_{t-1}^2 + \beta h_{t-1}^2$</p>
<p>A standard way of estimating the parameters of such a ... | g63934 | [
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0.04320124536752701,
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0.04437331482768059,
0.066... |
<p>I noticed that there is a definition of the p-value in my textbook. It is defined as the p-value of a composite null hypothesis and it says the following:</p>
<p><img src="http://i.stack.imgur.com/7Y4yL.jpg" alt="enter image description here"></p>
<p>I have no idea why it is written with a supremum. I've spent hou... | g49687 | [
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0.... |
<p>I have 3 visualization techniques (e.g., PC, NL and Map). I wanted to evaluate user performance (Time and Accuracy) for these three visualizations methods. I have 9 tasks for participants to perform. These 9 tasks categorized into 3 groups such group 1 , group 2 and Group 3 (each groups contains 3 tasks). I ran betw... | g21821 | [
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... |
<p>I'm having a tough time to understand concepts of Regression Analysis and Multivariate Analysis. I'm following the books of Johnston and Anderson, but some video lectures would help me learn it faster. Could anyone suggest me some videos of the same? Thanks.</p> | g63935 | [
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... |
<p>I am trying to express a hypothesis to test for the following claim: </p>
<blockquote>
<p>A biologist is presented with the data that shows an increase in the
average number of bacterias, though he suspects there was no actual
change.</p>
</blockquote>
<p>I came up with the following:</p>
<ul>
<li>$H_0:\; \... | g204 | [
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0.... |
<p>I understand this to be a binomial distribution: There are 100 balls in a bucket. 10 are red, 90 are blue. I select a ball at random and then replace it in the bucket, and I do this 20 times. I then calculate the probability that none of the selected balls were red.</p>
<p>But what if I don't put the ball back in t... | g21823 | [
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<p>I am new to R and using <code>rpart</code> for building a regression tree for my data.I wanted to use all the input variables for building the tree, but the rpart method using only a couple of inputs as shown below. As we can see, I have provided 10 inputs, but rpart used only two inputs. Please let me know how can ... | g63936 | [
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0... |
<p>I'm trying to estimate 4 maximum likelihood estimators on a data set containing two variables: <code>x</code> and <code>y</code>. When using the following code:</p>
<pre><code> logLikGrad <- function(param) {
b0 <- param[1]
b1 <- param[2]
sigma <- param[3]
landa <- param[4]
log... | g21825 | [
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... |
<h3>Context</h3>
<p>I want to set the scene before somewhat expanding on the question. </p>
<p>I have longitudinal data, measurements taken on subjects approximately every 3 months, primary outcome is numeric (as in continuous to 1dp) in the range 5 to 14 with the bulk (of all data points) being between 7 and 10. If ... | g63937 | [
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<p>Consider $\boldsymbol{x}= [x_1,x_2,...x_n]$ and $\boldsymbol{y}= [y_1,y_2,...y_n]$ to be two multivariate Gaussians with an isotropic diagonal variance structure and uninformative priors so that:</p>
<p>$p(x_i,\mu_{x_i},\sigma_x) = \frac{e^{\frac{-(x_i-\mu_{x_i})^2}{2\sigma_x^2}}}{\sqrt{2\pi \sigma_x}}$</p>
<p>and... | g45358 | [
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<p>I'm trying to do a repeated measure ANOVA analysis on the 5 NEO-FFI factors (Neuroticism, Extraversion, Openness to experience, Agreeableness and Conscientiousness). Sujest are tested only once, so I just want to compare the factors.</p>
<p>My question is how do I do the normality test? I mean, what is the dependen... | g63938 | [
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<p>I'm working on a binary classification problem, with about 1000 binary features in total. The problem is that for each datapoint, I only know the values of a small subset of the features (around 10-50), and the features in this subset are pretty much random.</p>
<p>What's a good way to deal with the problem of the ... | g63939 | [
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<p>Is there some way in R to output not only the main effects and the interactions of the two factors using an aov() like function but also the variance of the subject within a non-repeated factor?</p>
<p>For example, I have an experiment dealing with the factor Dose(the between subject variable - non repeated) and Ti... | g21827 | [
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<p>I am doing a time series analysis of sales data from a data warehouse. For that I want to use data grouped by the week of year. My problem now is that e.g. for week 1/2014, I have an outlier as this week only has two work days here in Austria.</p>
<p>Is such a thing a problem? If yes, what is considered as good pra... | g491 | [
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<p>This problem is basically the classic asset selling problem but with imperfect state information.</p>
<p>In the classical problem, we have an asset that we wish to sell, we receive offers w(0) to w(N-1). If we accept the offer at a given period, we can invest that money with a certain rate of interest r > 0. We s... | g41269 | [
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<p>I have a general question. What kind of noise is additive, and what about multiplicative noise? How to determine the nature of noise?</p>
<p>Thanks a lot for your help.</p> | g63940 | [
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<p>If I have a sample of k successes and n-k failures, there are standard techniques (Agresti-Coull, Clopper, etc.) for finding a confidence interval of the probability of an individual success. What if I want to find a confidence interval for the probability of getting at least k' out of n' instead? Obviously it can... | g41271 | [
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<p>I am testing whether there is difference between the scores of 2 groups of 12 questions on a Likert-scale questionnaire. Each question from one group has a corresponding question in the other group (12 pairs altogether) and my hypothesis is that the first group of questions has a higher score than the second one(one... | g21832 | [
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<p>I'm examing the relationship of payout policy and cash-flow uncertainty. My research' s data is cross section data and I use Tobit model to test the impact of explanatory variables (cash-flow uncertainty) to dependent variables (payout policy), and Logit model to test the probability of paying dividends. So when I u... | g63941 | [
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<p>Suppose the following problem: I have $n$ models, $M_k$, each with parameters $\mathbf{\theta}_k$ for a data set $D$. There where previous observations of a subset of the parameters which are common to every model $M_k$ (i.e., I have well defined priors for a subset of the parameters $\theta_k$), so I performed an M... | g63942 | [
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<p>I was working in R packages <strong>nlme</strong> and <strong>lme4</strong>, trying to specify the models with multiple random effects. I found, that only <strong>nlme</strong> allows to specify the heterogeneous structure of the variance. Therefore, I got a model, where temperature (Y) depends on time (in hours), i... | g41274 | [
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<p>I should show that the variance of the least squares estimator in the simple regression model $y_t = b x_t+u_t$ with the variables in deviation form is</p>
<p>$\operatorname{Var}(\hat{b}) = \operatorname{E}[(\hat{b} - b)^2] = \sigma^2 / \sum(x_t^2)$</p>
<p>($t$ is the time based indicator)</p>
<p>I know that $\ha... | g63943 | [
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<p>How is the var/cov error matrix calculated by statistical analysis packages in practice?</p>
<p>This idea is clear to me in theory. But not in practice. I mean, if I have a vector of random variables $\textbf{X}=(X_{1}, X_{2}, \ldots, X_{n})^\top$, I understand that the variance/covariance matrix $\Sigma$ will be g... | g476 | [
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<p>In statistics, there are methods that are named with "adaptive", such as "adaptive randomization" in experimental design, and "adaptive learning". What is the word that is opposite to "adaptive", and used in the opposite methods? Thanks!</p> | g63944 | [
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<p>I am working on a project regarding the influence of temperature and time variables (weekday, weekend, month, season etc.) on the sales of a local bakery. The research goal is to be able to better predict bakery sales (in my city) and to save food in this way.</p>
<p>What data do I have?
I do have the data of all v... | g63945 | [
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<p>I'm trying to understand confidence intervals but having some trouble. I've been doing some exercises I found online and I'm stuck on this question:</p>
<p>I have been given a 95% confidence interval for a population proportion: (0.35, 0.40), a sample size of 200, and I need to find a 99% confidence interval. The me... | g63946 | [
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<p>In my master thesis I have drawn a few hypotheses. I have answered them all with linear regression. In these linear regressions, I took control variables into account. </p>
<p>My question is: do I have to run a mediation analysis? Or is it also possible to report the regressions of all relations separately (for exa... | g63947 | [
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<p>I have a sample of 200 independent networks and I want to test the hypothesis that majority of vertices belong to one <a href="http://en.wikipedia.org/wiki/Giant_component" rel="nofollow">giant component</a>. I wonder what is the appropriate approach to do that.</p>
<p>More formally, suppose we have two variables, ... | g41279 | [
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<p>I will be too happy help me find the exact value or a very tight exponential upper bound for:
$$\sum_{k=1}^{N-1} \alpha^k \beta^{\frac{1}{N-k}}$$
where $0 \leq \alpha < 1$, $\beta= \exp(-N^2\zeta)$ and $\zeta$ is a positive small value.</p>
<p>Thanks a lot in advance.</p> | g63948 | [
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<p>I have recently begun using the Structural Equations Modeling (SEM) Method of confirmatory factor analysis for a research endeavor in educational science. My question is, suppose I have two latent variables each with many of its own manifest variables. If I observe a covariance between the two latent variables (I'm ... | g21836 | [
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<p>Let's assume I standardize my data in SPSS through converting them to z-values. Then I save my dataset and load it into AMOS to do some regressions. Now, the data is already standardized, but AMOS will give me two sets of regression coefficients, labeled as standardized and unstandardized.</p>
<p>Does this mean tha... | g15998 | [
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<p>I've met the following <em>randomized trace technique</em> in M. Seeger, “Low rank updates for the Cholesky decomposition,” University of California at Berkeley, Tech. Rep, 2007.</p>
<p>$$\operatorname{tr}(\mathbf{A}) = {E[\mathbf{x}^T \mathbf{A} \mathbf{x}]}$$</p>
<p>where $\mathbf{x} \sim N(\mathbf{0},\mathbf{I}... | g63949 | [
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<p>I have a time series which is daily data for workdays only. There is an almost obvious seasonality comparing the plot of the raw data that appears at the end of each month. However, there are not the same number of workdays for every month. Some times a month has 20 or 21 workdays. Do you have any idea how to treat ... | g63950 | [
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<p>I have a sample of data which was generated from a continuous random variable X. And from the histogram I draw using R, I guess that maybe the distribution of X obeys a certain Gamma distribution. But I do not know the exact parameters of this Gamma distribution. </p>
<p>My question is how to test whether the distr... | g63951 | [
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<p>It seems like a proposed study gets penalised if it doesn't also predict the direction of an effect. For instance, if I want to see the effect of a certain medication on happiness ratings, but do not predict whether I think they'll be decreasd or increased by that manipulation. Why is it considered unsound to run an... | g16542 | [
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<p>Possible warning: basic question ahead.</p>
<p>Let's say that I model whether I wear red shoes depending on the weather. Red shoes, which is my dependent variable, is a dichotomous variable as I either wear them or don't. Weather is a variable with five 'levels' and I'm trying to find the probability that I will we... | g63952 | [
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<p>The question I'm referring to comes from Stack Overflow:
<a href="http://stackoverflow.com/questions/8723652/estimating-number-of-results-in-google-app-engine-query">http://stackoverflow.com/questions/8723652/estimating-number-of-results-in-google-app-engine-query</a></p>
<p><em>In short:</em>
<strong>With $N$ ord... | g98 | [
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<p>In a paper I came across the description of $R^2$ as "it estimates the combined dispersion against the single dispersion of the observed and predicted series". I am not able to understand this statement. I understand that $R^2$ is the square of the correlation coefficient of predicted and observed values.</p>
<p>Pl... | g63953 | [
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0.07121283560991287,
0.019570400938391685,
-0.0356353260576725,
-0.06327147781848907,
-0.046762194484472275,
0.07466873526573181,
0.05207085236907005,
-0.001... |
<p><strong>First</strong>, a general linear algebra question: Can a matrix have more than one set of (unit size) eigenvectors? From a different angle: Is it possible that different decomposition methods/algorithms (QR, NIPALS, SVD, Householder etc.) give different sets of eigenvectors for the <em>same</em> matrix?</p>
... | g21844 | [
0.011155837215483189,
-0.027338102459907532,
-0.010895133949816227,
0.008625351823866367,
0.0338006429374218,
-0.08091752231121063,
0.02454032003879547,
-0.014679471962153912,
0.0187714584171772,
0.010891780257225037,
-0.023156464099884033,
-0.042332541197538376,
0.04102052375674248,
0.042... |
<p>I'm looking at some data conversion rates for an ad over time.</p>
<pre><code> view clicks
Day 1 100 10
Day 2 150 13
Day 3 90 9
Day 4 130 20
Day 5 150 21
</code></pre>
<p>Given that there is quite a bit of variation in the conversion ... | g63954 | [
-0.007847202010452747,
-0.03432603180408478,
-0.01642819121479988,
-0.022930903360247612,
0.0031679458916187286,
-0.01562965288758278,
0.06284549087285995,
-0.003844920312985778,
-0.018069906160235405,
-0.04514121636748314,
0.007097396533936262,
0.052548352628946304,
0.03538532927632332,
-... |
<p>I have to simulate (in javascript) the likelihood that members of a certain population would have a disease, given a contextual value. All information I have comes from papers that show odds ratios with $95\%$ confidence interval.</p>
<p>I found <a href="http://en.wikipedia.org/wiki/Box%E2%80%93Muller_transform" re... | g63955 | [
0.02946978434920311,
-0.0067490627989172935,
-0.028897633776068687,
-0.044871192425489426,
-0.05974053964018822,
-0.024253908544778824,
-0.020436769351363182,
0.00042318328632973135,
-0.005246082320809364,
-0.0382368229329586,
0.03957096487283707,
-0.002769517945125699,
0.07090701907873154,
... |
<p>I am in the midst of conducting a study which compares content in a printed catalog of records to content in a much larger online catalog of similar records. I have randomly selected 50 entries from the printed catalog and searched the online catalog to see if there are exact matches for these records. The results a... | g201 | [
-0.008596938103437424,
-0.013262039981782436,
-0.006722366902977228,
-0.05022686347365379,
-0.022406164556741714,
0.013903679326176643,
0.015069730579853058,
0.017824428156018257,
0.012001687660813332,
-0.021411476656794548,
-0.02279161661863327,
-0.0733630433678627,
0.04196222126483917,
-... |
<ul>
<li>What is the difference between a repeated measures ANOVA over some factor (say experimental condition) and a MANOVA?</li>
<li>In particular one website I stumbled across suggested that MANOVA does not make the same assumption of sphericity that repeated measures ANOVA does, is that true?<br>
<ul>
<li>If so, wh... | g49529 | [
-0.002633983502164483,
-0.0029282874893397093,
-0.00026773044373840094,
-0.03995063155889511,
-0.014041908085346222,
0.004733641631901264,
-0.005150428507477045,
0.018907584249973297,
-0.021721847355365753,
-0.01907983236014843,
-0.049075398594141006,
-0.022769136354327202,
-0.02511545084416... |
<p>I would like to estimate a multivariate model with the following properties:</p>
<ul>
<li><p>Fixed effects: </p>
<ol>
<li>Intercept </li>
<li>Main effect of condition</li>
<li>Main effect of Task order</li>
<li>Task order X Condition interaction </li>
</ol></li>
<li><p>Random effects: </p>
<ol>
<li>Main effect of... | g41293 | [
-0.02912546508014202,
-0.04917684569954872,
-0.012835988774895668,
-0.058965470641851425,
0.0038573003839701414,
-0.05477543920278549,
-0.0012608511606231332,
0.019103195518255234,
-0.018217148259282112,
0.003548251697793603,
0.028149167075753212,
0.0018444204470142722,
0.0238962322473526,
... |
<p>There's already been an <a href="http://stats.stackexchange.com/questions/3947/help-me-understand-support-vector-machines">excellent discussion</a> on how support vector machines handle classification, but I'm very confused about how support vector machines generalize to regression.</p>
<p>Anyone care to enlighten ... | g41294 | [
0.042564310133457184,
0.011439324356615543,
-0.017126018181443214,
0.02561461180448532,
0.03162172809243202,
-0.0027579760644584894,
0.02895994484424591,
0.052406128495931625,
-0.0681566372513771,
-0.03858184441924095,
-0.007245403248816729,
0.04731832444667816,
0.059274185448884964,
0.004... |
<p><code>FullModel<- (lm(Fubar~.-Foo-Bar,data=BarFoo))
NullModel<-(lm(Fubar~1))
step(NullModel,scope=formula(FullModel),direction="forward",k=log(nrow(BarFoo)))</code></p>
<p>When doing the above forward stepwise regression, the forward steps halt before certain variables are added in. does this mean that they d... | g21859 | [
0.023014672100543976,
-0.016399763524532318,
-0.00629380764439702,
-0.06650445610284805,
0.025731593370437622,
-0.015736166387796402,
0.04203493148088455,
0.01523053552955389,
-0.07991405576467514,
-0.07655764371156693,
-0.021367551758885384,
-0.011022377759218216,
0.04182100296020508,
0.0... |
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