question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I have a huge amount of features that are categorical variables and I'm trying to find a system for weeding out categorical variables that are close to being multicollinear.
Is vif a reasonable measure in the context of categorical variables?
Would pearson's chi-squared be a good measure of association between categ... | 72,334 |
<p>I have an implementation of latent Dirichlet allocation and I was wondering if there are any standard corpora that people have used to test LDA. Also, I would like to know how to get them.</p> | 72,335 |
<p>So I know a GARCH process is stationary, however I'm having doubts for the I-GARCH process as there is need for the coefficients of the process to sum up to 1, which does not satisfy the stationary condition. What's the difference between an I-GARCH and a normal GARCH?Why would you use one and not the other?</p> | 34,214 |
<p>J. B. Ramsey (in <em>"Tests for specification errors in classical linear least-squares regression analysis." Journal of the Royal Statistical Society. 1969</em>) says that the <a href="http://en.wikipedia.org/wiki/Ramsey_RESET_test" rel="nofollow">RESET test</a> assumes that the residuals are normally distributed. <... | 72,336 |
<p>I have one sample with n=170 and two binary variables (A,B) that can take as a value 1 or 0, where 1 counts as a success and 0 counts as a failure. What I want to know is whether the means of these two variables are equal.</p>
<p>To find this out I generate a new variable that takes the difference between these two... | 72,337 |
<p>I have categorical count data (for categories C1 to C3, but potentially several more categories) for two datasets:</p>
<pre><code> | --- Dataset 1 --- | --- Dataset 2 --- |
| C1 C2 C3 | C1 C2 C3 |
Item 1 | 0 200 300 | 0 2 3 |
Item 2 | 0 200 300 | 5 ... | 72,338 |
<p>I have the following train and test sets:</p>
<pre><code>train: 1000 obs. of 40 variables
test: 9000 obs. of 40 variables
</code></pre>
<p>Using 75% of <code>train</code> data, I could create a model that achieves 93% of success in classifying the <code>test</code> data.</p>
<p>Is it possible, as I have seen su... | 34,218 |
<p>The relative merits of GEE with exchangeable correlation or GEE with independence and the sandwich estimate have been discussed, but I couldn't find a post specifically addressing my question.</p>
<p>I have analyzed longitudinal data using GEE with AR-1 correlation structure and the sandwich/robust estimates of the... | 72,339 |
<p>In my math-stat class we have a theorem that goes:</p>
<p>Let $\{P_\theta : \theta \in \Theta\}$ be a $k$ parameter exponential family (i.e. the density of a member of this family can be written as $f(\mathbf{x}) = h(\mathbf{x})e^{\sum_{i=1}^k c_i(\theta)T_i(\mathbf{x}) - B(\theta)}$), suppose $\{c_1(\theta),\ldots... | 72,340 |
<p>this is a question regarding using <strong>lme()</strong> in <strong>R</strong> to calculate between-group and within-group variation in a dataset containing <em>log values</em>.</p>
<p>I have read that when using lme() to calculate sigma (variation) values in a dataset, if the values in the dataset (read in R from... | 72,341 |
<p>Quick question that I hope someone can help with. Imagine you have data from a randomized controlled trial (RCT) and you are interested in examining the impact of the treatment on a test score. Say that you administer the same test to participants prior to the treatment and after the treatment. I have presented mean... | 72,342 |
<p>Two quick questions:</p>
<ol>
<li>What's the maximum likelihood estimator of the parameter of an homogeneous Poisson counting process?</li>
<li>To estimate $\lambda$ I'm currently using number of events/total time, $N(t)/\Delta t$. What distribution does this statistic follow?</li>
</ol> | 34,225 |
<p>I am comparing three proportions for age categories for categorical variables that have also categories.
I used Chi-square test but I found that SPSS gave me a note which is for example:
a. 2 cells (33.3%) have expected count less than 5. The minimum expected count is .23.</p>
<p>What is the solution></p> | 72,343 |
<p>It is i'm sure quite a simple question but i was not really able to find an explanation of this online and does not seem to be explicitly called out in the typical expositions i've seen. </p>
<p>I get how 10 fold cross validation works to recursively partition the dataset into 9 train and 1 test set 10 times to get... | 49,893 |
<p>What is the difference between:</p>
<ul>
<li>1) xcov(x,y,10,'unbiased')/sqrt(xcov(x,x,0,'unbiased')*xcov(y,y,0,'unbiased'));</li>
<li>2) xcorr(x,y,10,'unbiased');</li>
<li>3) [<strong>A</strong>, B] = crosscorr(x,y,10);</li>
</ul>
<p>?</p>
<p>I think (but I am not sure) that "crosscorr" removes the means and "xco... | 72,344 |
<p>For linear model $y=x*\beta+e$, we can have a nice geometric interpretation of estimated model via OLS: $\hat{y}=x*\hat{\beta}+\hat{e}$. $\hat{y}$ is the projection of y onto the space spanned by x and residual $\hat{e}$ is perpendicular to this space spanned by x. </p>
<p>Now, my question is: is there any geometri... | 72,345 |
<p>I have similar findings to JDneversleep - I have 2 main effects of, language difficulties and gender. The effects of language difficulties and gender on social skills are negative. But I am getting positive coefficient for the interaction between language and gender. Could someone explain to me in terms of my vari... | 49,894 |
<p>When I do a (logistic) regression in R, I run something like this:</p>
<pre><code>mydata <- read.csv("data.csv")
mylogit <- glm(a ~ c+d, data = mydata, family="binomial")
summary(mylogit)
</code></pre>
<p>As of a few months ago, the output for the coefficients might look like this:</p>
<pre><code>Call:
glm(... | 72,346 |
<p>If a factor variable (e.g. gender with levels M and F) is used in the glm formula, dummy variable(s) are created, and can be found in the glm model summary along with their associated coefficients (e.g. genderM)</p>
<p>If, instead of relying on R to split up the factor in this way, the factor is encoded in a series... | 72,347 |
<p>Let $X$ be lognormal with parameters $\mu$ and $\sigma$ (such that $\log(X)$ is Gaussian with mean $\mu$ and variance $\sigma^2$).</p>
<p>What is the distribution of $1 / (X + 1)$? I am wondering whether it is a "simple" parametric distribution. If the "+1" were replaced with zero, the problem becomes quite easy.</... | 72,348 |
<p>Can you give me an example of the use of sandwich estimators in order to perform a robust regression?</p>
<p>I can see the example in <code>?sandwich</code> but I don't quite understand how we can go from </p>
<pre><code>lm(a ~ b, data) # R-coded
</code></pre>
<p>to an estimate and a p.value resulting of a robust... | 72,349 |
<p>I haven't been able to answer this daunting question for days now and I am not able to find the right resource for it, so maybe someone here might help me out.</p>
<p>Consider an outer product of two <strong>uniform</strong> random vectors <strong>mod p</strong>, where the vector consists of independent uniform ran... | 72,350 |
<p>As part of a University assignment, I have to conduct data pre-processing on a fairly huge, multivariate (>10) raw data set. I'm not a statistician in any sense of the word, so I'm a little confused as to what's going on. Apologies in advance for what is probably a laughably simple question - my head's spinning aft... | 49,305 |
<p>this is an example experiment design for which I would need some help (the values are the same between assays but should be different). </p>
<p><img src="http://i.stack.imgur.com/IC9Ey.png" alt="enter image description here">
I want to test if the use of drug 1 or drug 2 has a significant effect on the output being... | 72,351 |
<blockquote>
<p>Given the simple regression
$$Y_t = \beta X_t + e_t$$,
with $$e_t = \epsilon_t + \theta_1 \epsilon_{t-1} + \theta_2 \epsilon_{t-2}, \epsilon_t \sim WN(0, \sigma^2)$$ and $$X_t iid, X_s \perp e_t \forall s,t$$
Is ${X_t e_t}$ a Martingale Difference Sequence w.r.t $F_{t-1}=(X_{t-1}, e_{t-1}, X_{... | 72,352 |
<p>Are these assumptions correct and the list complete for <strong>repeated-measures MANCOVA</strong>?</p>
<ul>
<li>sphericity</li>
<li>multivariate normality</li>
<li>homogeneity of variance</li>
<li>homogeneity of covariance matrices</li>
<li>homogeneity of regression slopes</li>
<li>independence of independent vari... | 72,353 |
<p>I have used SPSS Clementine in order to train a classifier, for this I have used a partition node with 2 parts(train and test),then using a c5-tree and cross-fold validation.</p>
<p>I did this because I think SPSS separates training data and does a 10-fold validation to build a best model and then test it by test d... | 72,354 |
<p>Is it really important to normalize dependent variables in multiple regression or are there any exceptions? </p>
<p>My model is providing better results with more significant hypothesis when the DVs are not normalized (transformed). Will be grateful for the comments.</p> | 72,355 |
<p>I want to find a way to convert the Likert scale to Pairwise (AHP/ANP) scale, because my questionnaire contains 30 criteria to compare, and making a pairwise questionnaire will contain (30*(30-1))/2 questions, which are very long to answer for the respondents. </p>
<p>Does anyone know how to deal with that? or any ... | 72,356 |
<p>I've a question here. Basically I have the mean and standard deviation of a variable (IQ). I want to find the probability that 8 out of 10 people randomly selected have IQ scores between 85.0 and 122.5. </p>
<p>I also have the following information worked out:</p>
<ul>
<li>mean = 100</li>
<li>standard distribution... | 72,357 |
<p>I'm trying to model football scores using the poisson distribution. I'm calculating a lambda for each team and then multiplying the probabilities of two poisson calculations to get the probability of a specific score.</p>
<p>e.g. poison(lambdaHome, 1)*poisson(lambdaAway, 2) to calculate the probability of a 1-2 res... | 72,358 |
<p>As an assumption of linear regression, the normality of the distribution of the error is sometimes wrongly "extended" or interpreted as the need for normality of the y or x.</p>
<p>Is it possible to construct a scenario/dataset that where the X and Y are non-normal but the error term is and therefore the obtained l... | 72,359 |
<p>My research project is to come up with a tool for analyzing publication and subscription patterns of Sri Lankan news web sites.
As a part of my project, my tool should be capable of finding out the followings, in addition to analyzing the publication patterns of news websites.</p>
<p>• Mostly subscribed new... | 34,241 |
<p>What tests would I use to see if two distributions are 'significantly' different in dispersion if they are thick tailed, like a t-distribution? thanks</p> | 72,360 |
<p>I have a data set with about 50K rows and 100 columns. You can consider every row to be representing one restaurant.</p>
<p>My goal is to calculate dissimilarities between all the restaurants - Gower's coefficient.</p>
<p>Of those 100 columns (features), a few of them are numeric data and nominal data. The problem... | 34,242 |
<p>I am trying to track down examples where some basic problems have been tackled via both classical Machine Learning algorithms and more formal statistical methods. In particular, I'm interested in examples where SVM has been contrasted with hierarchical Bayesian methods. (but I'll happily take non-SVM examples.) </... | 72,361 |
<p>An extra sum of squares $SSR(X_p|X_1,...X_{p-1})$, assuming that no pair of predictor variables are perfectly correlated, measures the marginal reduction in the error sum of squares. Eventually one can view an extra sum of squares as measuring the marginal increase in the regression sum of squares when one or severa... | 72,362 |
<p>I believe I read today a phrase which went something like this:</p>
<blockquote>
<p>If a distribution has a mean and a variance ...</p>
</blockquote>
<p>So I guess that means some distributions do not have means or variances?</p>
<p>I fiend that a bit difficult to understand - for example:</p>
<p>I could get d... | 34,250 |
<p>I'm trying to understand the concept of independence experimentally using computer simulation.</p>
<p>I imagine to understand this concept:</p>
<ol>
<li>I should be able to generate three data sets from random Variables A, B and C where A and B are independent and A and C are not independent.</li>
<li>I should be ... | 72,363 |
<p>I am carrying out a statistical analysis for my research. I am using a Friedman's test with post hoc analysis. At present I am using the function <code>friedman.test.with.post.hoc</code> available for R software. This function reports "maxT" value instead of the chi-square value. Someone can explain me what is maxT ... | 166 |
<p>I would like to explore the different ways one can <strong>detrend</strong> a time series <strong>without look ahead bias</strong>.</p>
<p>I wanted to use the Hodrick Prescott filter, which seems like a quite good frequency filter, but it is based on an optimization method, and I understand that it may give strange... | 1,013 |
<p>I'm about to use variance partitioning to interpret my results of a given model and across models and have come across various criticisms of it most notably by Pedhazur (1982, 1997). Also, the criticisms are of both the approaches to VP - commonality analysis and incremental partitioning of variance. From what I und... | 72,364 |
<p>When does/can one use the likelihood ratio significance test instead of Fisher's exact test or its Pearson $\chi^2$ approximation for comparing two binomial datasets?</p>
<p>Given two binomial datasets (distributions), I'm seeing the LR test being used to compare one distribution against the global (combined) distr... | 72,365 |
<p>Using OLS, I've estimated the following equation:</p>
<p>$y_i = \alpha_0 + \alpha_1 X_i + \epsilon_i$</p>
<p>I know that theoretically, the following should be true: </p>
<p>$y_i = a + (1-e^{-\lambda 60}) X_i$</p>
<p>Is there any way, having an estimate of $\alpha_1$ I can translate it to an estimate of $\lambda... | 72,366 |
<p>I came across term <strong>perplexity</strong> which refers to the log-averaged inverse probability on unseen data. Wikipedia <a href="http://en.wikipedia.org/wiki/Perplexity" rel="nofollow">article</a> on <strong>perplexity</strong> doesnt give a intuitive meaning for the same. This perplexity measure was used in <... | 48,057 |
<p>I'm reading a paper <em>Gibbs sampling for the uninitiated</em>.</p>
<p>In this paper, the authors try to use Gibbs sampling for a bayesian naive bayes model. They formalize the model as a graphical model in page 8. And in the example, they are trying to predict the emotion(sentiment) of a document. </p>
<p>Howeve... | 34,252 |
<p>I want to generate random numbers according to a distribution curve like the <a href="http://office.microsoft.com/en-sg/excel-help/norm-s-inv-function-HP010335692.aspx" rel="nofollow">inverse cummulative normal curve</a>. But the curve should allow parameters to adjust the parameters as shown in the image, namely, t... | 72,367 |
<p>I'm trying to calculate the log-likelihood for a generalized nonlinear least squares regression for the function $f(x)=\frac{\beta_1}{(1+\frac x\beta_2)^{\beta_3}}$ optimized by the <code>gnls</code> function in the R package <code>nlme</code>, using the variance covariance matrix generated by distances on a a phylo... | 72,368 |
<p>I'm fooling around with threshold time series models. While I was digging through what others have done, I ran across the CDC's site for flu data.</p>
<p><a href="http://www.cdc.gov/flu/weekly/" rel="nofollow">http://www.cdc.gov/flu/weekly/</a></p>
<p>About 1/3 of the way down the page is a graph titled "Pneumoni... | 72,369 |
<p>This is my first question here. I have experimental results for two datasets where I want to check if the difference is significant or not. Here is a description of my experiment:</p>
<p>Experiment: I have a set of 70 genes where I showed that 12 of them are evolving in a particular manner. Now I wanted to check if... | 72,370 |
<p>I'm working through a practice problem for my Stats homework. We're using Confidence Intervals to find a range that the true mean lies within. I'm having trouble understanding how to find the required sample size to estimate the true mean within something like +- 0.5%.</p>
<p>I understand how to work the problem wh... | 34,257 |
<p>In R's <a href="http://cran.r-project.org/web/packages/survival/survival.pdf" rel="nofollow"><code>survival</code></a> and <a href="http://cran.r-project.org/web/packages/rms/rms.pdf" rel="nofollow"><code>rms</code></a> packages, Kaplan-Meier (<code>Surv</code> and <code>survift</code>) and Cox Proportional Hazards ... | 34,259 |
<p>My actual project is a bit complicated, but I'll explain by analogy (which I hope facilitates response):</p>
<p>I have 3 substances, say water, motor oil, and ethanol. For each substance, I have 5 samples in a beaker (total 15 beakers). I heat all the beakers on a hot-plate up to 70 degrees Celsius, and over the ne... | 30,808 |
<p>I'm currently working through a machine learning textbook and just read a bit about k-fold cross validation, and I am wondering the following. I want to estimate a parameter, e.g. a penalty parameter for a penalized likelihood method. In order to do this, I can do two different things:</p>
<ol>
<li><p>I sample the ... | 72,371 |
<p>I am trying to figure out a away to calculate the average a set of data in the most robust way that I can, while staying accurate (this has to do with billing software). </p>
<p>For example, let's say I have the monthly minutes available to me. I need to find a good monthly average in order to figure out how many m... | 34,260 |
<p>I want to create a CRBM that learns sequences of data. Since the data can be quite complex, I want to use several layers, but I am struggling how to use several layers.</p>
<p>I found <a href="http://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&ved=0CDsQFjAB&url=htt... | 34,261 |
<p>Can a moving average value result be higher than the highest constituent value on which the moving average is based?</p>
<p>I realize that somewhere here there maybe an answer, but I have been unable to find one specific to this question. I do not believe that a "moving average value result" based on a set of valu... | 72,372 |
<p>In the course of my work, something of a problem has arisen. It can be summarized like this: there's a large pool of job applicants, let's say N of them. What needs to be done is that these applicants be ranked in order of desirability to the company: 1, 2, 3,... N. Until now, this has been done rather laboriously b... | 72,373 |
<p>I am comparing the difference in time-activity-budgets of two populations of seabirds, those in the presence of ship disturbance and those not in the presence of ship disturbance. Focal animals were chosen haphazardly and observed for up to 10 minutes. Not all animals were observed for 10 minutes but the purpose of ... | 72,374 |
<p>I have a set of parties $V=\left\{ {V_i, V_j,..., V_n}\right\}$. Each party has a corresponding attribute $S=\left\{ {S_i, S_j,..., S_n}\right\}$ indicating the number of people participating to the event. For each pair of events $V_i$ and $V_j$ I can infer the number of participants in common as $E_{ij}$, with $E_{... | 72,375 |
<p>I have a serie of objects for whom I know the probability of belonging to 10 classes. This probability can be null (see example below with 4 classes). </p>
<pre><code> A B C D
1 0.4 0.0 0.2 0.4
2 0.1 0.3 0.4 0.2
3 0.0 0.0 0.0 1.0
</code></pre>
<p>In order to get for each object an informatio... | 72,376 |
<p>I am trying to fit a negative binomial GLM to fish catch data with month of the year (factor) as my explanatory variable. I have selected the month with the greatest number of catches as my reference level and fitted the model using the <code>glm.nb()</code> function from the MASS package.</p>
<pre><code>model1<... | 72,377 |
<p>I created a quick fun Excel Spreadsheet tonight to try and predict which video games I'll enjoy if I buy them. I'm wondering if this quick example makes sense from a Logistic Regression perspective and if I am computing all of the values correctly.</p>
<p>Unfortunately, if I did everything correctly I doubt I have ... | 72,378 |
<p>I am analyzing scores given by participants attending an experiment. I want to estimate the reliability of my questionnaire which is composed of 6 items aimed at estimating the attitude of the participants towards a product. </p>
<p>I computed Cronbach's alpha treating all items as a single scale (alpha was about ... | 72,379 |
<p>In a simulation, I generate data from distribution A, and then I hope to test if each of some other distributions B,C,D... can fit the data equally well. Obviously there is an initial fit of the model under distribution A, so I can get the Pearson's chi^2 statistic as a measure of goodness-of-fit. </p>
<p>My questi... | 72,380 |
<p>Is it possible to speak of the independence of a single sample (of multiple data points) relative to the underlying distribution? Or is independence only relevant <em>between</em> samples?</p> | 34,272 |
<p>Say I want to estimate a large number of parameters, and I want to penalize some of them because I believe they should have little effect compared to the others. How do I decide what penalization scheme to use? When is ridge regression more appropriate? When should I use lasso?</p> | 37,924 |
<p>I'm trying to create some kind of iterative Bayesian algorithm, which continuously updates as more data is gathered. However, the distribution of my data is such that there does not exist a conjugate prior, so I'm thinking of using something like Gibbs sampling to generate my posterior distribution.</p>
<p>However,... | 37,987 |
<p>We have been working on a project where we have 2 or more trading agents on a market stock and for the outcome we have the profits that each trader generated after running 1000 times or more each market session.
We need to statistically compare the profits of this traders to know which one is better, we have the ide... | 34,281 |
<p>I want to use a set of daily water quality data including 3 parameters in a Copula model. Somebody told me these data do not have a condition of a random variable to use in copula, and I should do some work on it (my guess is that it involves detrending the data). </p>
<p>Can anybody help me in finding methods to ... | 72,381 |
<p>My survey is based on observations and interviews. The observation questions are yes/no type questions and interview questions are 4 points. </p>
<blockquote>
<p>$1=$ never, $2=$ sometimes, $3=$ usually, and $4=$ always.<br>
Yes $=1$, No $=0$. </p>
</blockquote>
<p>If I add up all these with highest possible ... | 45,390 |
<p>My question is, how to get effect sizes for a linear mixed model?</p>
<p>I am using the following model in SPSS:</p>
<pre><code>MIXED
transfer BY distance training rotation sequence WITH pretest
/CRITERIA = CIN(95) MXITER(100) MXSTEP(5) SCORING(1) SINGULAR(0.000000000001)
HCONVERGE(0, ABSOLUTE) LCONVER... | 72,382 |
<p>I was wondering which p-value to use when i am testing the significance of an interaction between two continuous variables.</p>
<p>Here is my model with the interaction:</p>
<p>Coefficients:</p>
<pre><code> Estimate Std. Error t value Pr(>|t|)
(Intercept) 110.2584 23.9969 4.595 ... | 34,283 |
<p>I am trying to understand how to get the coefficient of a multiple linear regression. </p>
<p>The formula is:</p>
<p>$b = (X'X)^{-1}(X')Y$</p>
<p>I try to calculate $b$ without package and with the <code>lm</code> package inside R. </p>
<p>Doing so, I got different results. </p>
<p>I want to know why. Did I mad... | 72,383 |
<p>I've run into an interesting model into some of my research and I was hoping somebody with more mileage can point me to any resources or other applications. </p>
<p>I'm familiar with the Beta-Binomial, but now I'm trying to do some analysis where the shape parameters associated with the Beta prior are RVs distribut... | 34,285 |
<p>Why is it correct not to measure the correlation between two distance matrices by calculating the Pearson's correlation coefficient between all distance pairs but to use the Mantel test instead?</p>
<p>Edit:
Wikipedia says that because "distances are not independent of each other – since changing the "position" of ... | 72,384 |
<p>I am interested in a family of multivariate distributions that can be seen as a generalization of the multivariate normal distribution, insofar as they are defined by an expectation value $\vec \mu$ and a covariance matrix $\Sigma$, plus a monotonously decreasing function $g(d)$ such that the density is
$$
p(\vec x)... | 34,287 |
<p>Given the variables $X$ and $Y$, which are correlated, $X\ge0$, $Y\ge0$ and each follow a gamma distribution with different shape parameters, i.e.,$X\sim Gamma(a_1,\alpha)$ and $Y\sim Gamma(a_2,\alpha)$. </p>
<p>I understood that the Joint PDF $f_{X,Y}(x,y)$ can be obtained by making use of the Farlie Gumbel Morgen... | 45,395 |
<p>I have seen several articles and CrossValidated questions on bootstrapping ( <a href="http://stats.stackexchange.com/questions/41625/can-i-use-boostrapping-why-or-why-not">this</a>, <a href="http://stats.stackexchange.com/questions/59829/which-bootstrapped-regression-model-should-i-choose">this</a> or <a href="http:... | 72,385 |
<p>I am using a simple feedforward neural network in MATLAB to predict the output for inputs in the range [1e-5, 0.3]. (These are the activations of another network.) I am using a sigmoid function for the hidden layer, and a linear function for the output layer. Input units are 6, hidden units are 4, and the output uni... | 72,386 |
<p>I have left censored data where the distribution is known (it's near enough lognormal, at least in theory).</p>
<p>I'd like to calculate some simple summary stats: geometric mean and standard deviation in this case.</p>
<p>I've previously used R's <code>NADA</code> package for this but it is no longer on CRAN. Is... | 72,387 |
<p>Suppose I observe a sample $(y_i,x_i)$, $i=1,...,n$. Suppose that I know the following:</p>
<p>$y_i=\alpha_0+\alpha_1x_i+\varepsilon_i$, $i \in J\subset\{1,...,n\}$
</p>
<p>$y_i=\beta_0+\beta_1x_i+\varepsilon_i$, $i \in J^c$
</p>
<p>where $\varepsilon_i$ are i. i. d. and $J$ is not known in advance. Is it possibl... | 45,399 |
<p>This is a fairly basic question but I can't seem to find an answer on the net (perhaps I'm searching the wrong things).</p>
<p>Regression is trying to predict continuous outputs. Since a neural network uses a clamping function (typically giving a value between 0 and 1) before the output.. if the output can only be ... | 10,176 |
<p>I have a regression with ARMA errors, which I am fitting with <code>arima()</code>. I know that the ARMA model is being fit on these residuals from the regression. My problem is that when I use <code>include.mean=TRUE</code> the output does not return any estimate of the mean (of the residuals, which yes, I know is ... | 72,388 |
<p>I have fairly good practical experience with Metropolis-Hastings and Gibbs sampling, but I want to get a better mathematical understanding of these algorithms. What are some good textbooks or articles that prove the correctness of these samplers (more algorithms would also be great)?</p> | 36,914 |
<p>In section 7.10.2 of Elements of Statistical Learning, it says that the true (test) error rate of any classifier is 50%. I'm having trouble understanding the intuition behind this. If you have a binary class (1 or 0) and your classifier is a die where if you roll a 1-5, the classification is 1 and if you roll a 6, t... | 72,389 |
<p>Below is the list of parameters in Mahout logistic regression.</p>
<ol>
<li><p>What does "passes" mean? In detail please </p>
<blockquote>
<p>--passes passes the number of times to pass over the input data</p>
</blockquote></li>
<li><p>What does "features" mean? Is it the number of varia... | 72,390 |
<p>My data was paired and do not fit normality. So I used a Friedman test.However, the result turn out to be Friedman chi-squared = 0, df = 1, p-value = 1. How do this happen?</p>
<p>My data was in this way:</p>
<pre><code> I II
1 2 1
2 4 1
3 5 0
4 0 2
5 14 3
6 11 3
7 7 6
8 8 ... | 72,391 |
<p>In a typical hierarchical cluster output from using SAS, the first table given lists all of the eigenvalues.</p>
<p>From what I understand, eigenvalues are derived from covariance between the variables. What I fail to understand is how this would assist me in understanding the underlying clustering behavior.</p>
<... | 72,392 |
<p>I have an annotation task which I need to analyze for accuracy, category fine tuning and reliability , there are many annotators assigning multiple set valued categories to items. And I have come up with confusion matrices for each pair of annotators like below:</p>
<pre>
+-----------------------------------------+... | 72,393 |
<p>I have 3 time series X, Y, Z</p>
<p>If the regression coefficient (slope) of X and Y is <strong>a</strong>, Y and Z is <strong>b</strong>, then what can I say about the regression coefficient of X and Z?</p> | 72,394 |
<p>I am doing a basic analysis for my research, regarding the relationship between the global oil & gas price and the Australian aggregate and sectoral equity markets.</p>
<p>My supervisor has me using EVIEWS 8 courtesy of its availability at university. </p>
<p>My data comprises of price indexes for World O&... | 72,395 |
<p>I'm fitting a natural basis spline on a data set of the form: </p>
<pre><code>splineModel=lm(dist~bs(speed, df=3), data=cars)
</code></pre>
<p>using <code>bs</code> function of <code>spline</code> package. I would like to know whether is possible to print the actual spline equations fitted (the tracing) within e... | 72,396 |
<p>I've repeatedly measured a continuous variable and each measure has been assigned a populational percentile range it falls into (percentile ranges were estimated for general population in another study). The exemplary barplot depicts the share of each group in my sample during different time points.</p>
<p>I'd like... | 36,915 |
<p>I have many pairs like:</p>
<pre><code>A B
10 20
15.3 19.5
23 13
45 32
</code></pre>
<p>etc etc,
I create those pairs calculating the standard deviation of many vectors (R vectors) and then group them by 2(A - B).</p>
<p>Now, I have to filter those pairs by their percentage difference.
I set a percentage like <... | 38,032 |
<p>Suppose I am modelling a binary outcome $y$ with $n$ covariates. If this model has the lowest AIC among all the other ones...would this be the one to use? Also in dealing with categorical variables, should you delete all levels or none? For example suppose a categorical variable $z$ has the following levels: $z_1, z... | 18,494 |
<p>I have this income distribution data for various groups:
<a href="https://docs.google.com/spreadsheet/ccc?key=0Akwg3n_e05cCdEdtT0VZYU5keW5DVkNoNmpBWmdzeUE" rel="nofollow">https://docs.google.com/spreadsheet/ccc?key=0Akwg3n_e05cCdEdtT0VZYU5keW5DVkNoNmpBWmdzeUE</a></p>
<p>As you can see, I have intervals/bins with va... | 45,414 |
<p>Disclaimer: I am a biologist, so please don't hesitate to correct me if I am making unwise assumptions.</p>
<p>I am looking at the distribution of a unique 6mer in a series of 2100mer (I have 415 independent 2100mer). More precisely, I am looking into how many times that 6mer is present in each 2100mer. As I deal w... | 72,397 |
<p>I have a dataset and I made the QQ-plot against the $N(0,1)$ distribution. The plot is included below.</p>
<p><img src="http://i.stack.imgur.com/MlXsY.png" alt=""></p>
<p>My statistics is rusty to say the least (meaning what little knowledge I had is now rusted away!) Clearly the normal distribution is not a good ... | 72,398 |
<p>There are several popular resampling techniques, which are often used in practice, such as bootstrapping, permutation test, jackknife, etc. There are numerous articles & books discuss these techniques, for example <a href="http://rads.stackoverflow.com/amzn/click/1441919074">Philip I Good (2010) Permutation, Par... | 48,614 |
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