question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I am trying to cluster cells (1×1km) over a specific area. Each cell is composed of various habitats defined by a code. (Each habitat consists of 3 parameters, so a habitat code looks like e.g. 1-3-15. There are around 100 different habitats, i.e. max number of combinations of these 3 parameters).</p>
<p>I no... | 36,119 |
<p>My boss gave me this do file but I have never worked with dprobit. I also need to interpret it, this is the result:</p>
<pre><code> xi: dprobit apoyado $X, robust nolog
i.fuerza _Ifuerza_1-9 (_Ifuerza_1 for fue~a==Comando General omitted)
note: _Ifuerza_8 != 0 predicts success perfectly
_Ifue... | 73,681 |
<p>I created a criterion for my financial data-set for classify data to two classes for other processing (like <code>neural network binary classificatio</code>). After calculating this criterion (between 0 and 1) the distribution of output is like <code>exponential</code> (but between <code>0</code> and <code>1</code> ... | 73,682 |
<p>I am trying to select a prior for the covariance parameters of my Gaussian Process (GP) and have been running into numerical problems with my MCMC code. My model is the following:</p>
<p>$$Y = D\beta + GP(0,\sigma^2R(\psi))$$</p>
<p>where $R$ is the following correlation matrix:</p>
<p>$$R_{i,j}(\psi)=\exp(\psi(... | 73,683 |
<p>I have $2\times 3$ repeated measures design.</p>
<ul>
<li>2 conditions(a and b)</li>
<li>3 intensities (low, medium and high).</li>
</ul>
<p>I am concerned only with the a to b differences at the corresponding intensity. For example I would like to compare:</p>
<ul>
<li>A low and b low</li>
<li>A medium and b me... | 36,125 |
<p>I have 3 variables A, B and C, which are all markedly skewed. Below, I indicate correlations between two variables, e.g., A and B as $r_{ab}$.
Using the following test with with $n-2$ degrees of freedom</p>
<p>$$t= \frac{r\sqrt{n-2}}{1-r^2}$$</p>
<ul>
<li>$r_{ac}$ is positive but not significantly different from ... | 73,684 |
<p><strong>UPDATE</strong> Original question was confused and poorly worded. I thought about it more and don't think I have a question any longer. After thinking a bit more I came up with:</p>
<p>For a distribution, such as the normal for example, the probability that the variable falls in a certain range is:</p>
<pr... | 73,685 |
<p>How can I interpret the main effects (coefficients for dummy-coded factor) in a Poisson regression?</p>
<p>Assume the following example:</p>
<pre><code>treatment <- factor(rep(c(1, 2), c(43, 41)),
levels = c(1, 2),
labels = c("placebo", "treated"))
improved ... | 49,412 |
<p>Let $X$ be a random variable from $f(x; \theta)$, where $\theta =(\theta_1,\theta_2)$.
I want to:</p>
<p>take a sample from this distribution using Metropolis Hastings algorithm and update the parameters simultaneously.</p>
<p>The proposal distribution is a bivariate normal distribution with mean the current value... | 29,780 |
<p>was wondering if someone could help clarify an ANCOVA for me, or maybe post me in the right direction.</p>
<p>I have a set of outcome measures that have been administered pre treatment and post treatment. I do not have a control group. My data is in a long format (i.e. each individual has data on 2 rows, one for pr... | 73,686 |
<p>I have a screen shot and the question asks if the sample size is blocked out, what is the most likely sample size that was used to generate these results. How do I do this? The possible answers are 5, 10 , 20 and 25 and 25 is the correct answer. It gives the mean 8.08, median 7, sd=6.22 skew=0.83 at the top.</p> | 73,687 |
<p>What kind of data analysis technique / formula would you use to describe which is the fastest OS in this chart, Windows or Linux? </p>
<p><img src="http://i.stack.imgur.com/uleOH.png" alt="enter image description here"></p>
<p>If Linux and Windows had equal speed on all tests, all bars would be 50% blue, 50% green... | 36,130 |
<p>What I mean is, constructing a decision tree where each node is not a single feature instead composition of multiple features, therefore the evaluation criteria should consider a metric over multiple numbers instead of single number. For the original case of decision tree we are looking for a feature's value compari... | 36,131 |
<p>Consider the following m regression equation system:</p>
<p>$$r^i = X^i \beta^i + \epsilon^i \;\;\; \text{for} \;i=1,2,3,..,T$$</p>
<p>where $r^i$ is a $(T\times 1)$ vector of the T observations of the dependent variable, $X^i$ is a $(T\times k)$ matrix of independent variables, $\beta^i$ is a $(k\times1)$ vector... | 73,688 |
<p>Previously I've read that adjusted-$R^2$ is not a measure of fit. Recently, though, I wanted to substantiate that piece of knowledge by understanding the reason why but I couldn't find any substantive sources to back this up. </p>
<p>The Wikipedia article on it states "while $R^2$ is a measure of fit, adjusted $R^2... | 36,133 |
<p>I was comparing the performance of pROC and AUC libraries when performing auc() calculations on random data:</p>
<pre><code>library("pROC");
library("AUC")
predictor <- rnorm(10000, 5);
outcome <- rnorm(10000) > 0;
print ("pROC:::auc() time & output")
system.time(x <- pROC:::auc(outcome, predictor... | 690 |
<p>I have a series of numbers, which are some survival probabilities that form a decaying curve. I would like to fit them with a "Pareto" distribution. I expect to have a smooth fitted curve, thus I can extrapolate it and have a rough prediction.</p>
<p>My data are like <code>1, 0.987, 0.972, 0.965, ...</code>.</p>
<... | 36,136 |
<p>I am currently working on a retrospective analysis where I am looking at patients to see if immune sensitization prior to a procedure has any bearing on outcomes after the procedure. The immune sensitization is a categorical variable (Hi vs Lo). </p>
<p>In regards to outcomes, one of the things I am looking is surv... | 18,991 |
<p>I would like to run a negative binomial regression, but also controlling for one of the variables. Similar to what you would do with a hierarchical regression. I am trying to predict violence (never, once, 3 times ...); and the literature says I should control for age, as aggression decreases with age.
Would welcom... | 20,443 |
<p>I'd like to see how not adjusting for confounders affects estimated coefficients in linear regression. Here is what my lecture notes say:</p>
<ol>
<li>Un-adjusted model: $E[Yi] = \beta_0 + \beta_1X_i$</li>
<li>Adjusted model: $\quad\ E[Yi] = \gamma_0 + \gamma_1X_i + \gamma_2W$, where $W$ is the confounder.</li>
</o... | 48,671 |
<p>I have created a vector of length 400 with 6 unique values of relatively equal proportions (1-6). I have drawn two random samples from the vector, each $n=26$, 10,000 times, performed $t$-tests, added the $p$-values to a list and output a histogram of the $p$-value frequency. The histogram of the $p$-values shows a ... | 73,689 |
<p>Say I have a data matrix of size $N \times P$ where $N$ is the number of samples and $P$ is the number of features. Now, if I do principal component analysis, I get another data matrix of size $N \times K$ where $K$ was chosen according to some criteria. My question: if I pick a row (sample) from the $\text{PCA}$ ma... | 73,690 |
<p>In the <a href="http://en.wikipedia.org/wiki/Pitch_%28card_game%29" rel="nofollow">game of Pitch</a> what are the odds of the jack of trump being dealt in the 24 cards?</p> | 73,691 |
<p><strong>Variogram</strong> is simple but effective way to investigated the spatial variation in the variable of interest in the field being studied. However it has been reported that variogram cannot be considered as the most satisfactory model especially where there are curvature <em>(e.g., permeable channels in re... | 73,692 |
<p>I've got two time-series, S (stress in a railway track) and T (temperature).
The time-series are several months long. The relationship is linear, however, it can change subtly or 'jump' at some points, due to work done on the rails.</p>
<p>Currently, I'm doing linear regression on a per-day basis, and then tempera... | 40,061 |
<p>I have a data set of 903 continuous observations, that I graphically visualize with a histogram. The bin and width values could be optimized, but it is logical from the distribution that I have a Gaussian function.</p>
<p>When I do the fitting, I use the frequency values of the data as the Y-values. For example, if... | 73,693 |
<p>I only found a example in which the constraind on $\beta_i, \ i=1,...k$ would make them sum up to one as well introduces a constraind such that all $\beta_i$ are all greater or equal zero. Since I dont need a condition for the summation of the $\beta_i$ I'm not quite sure how to deal with this problem.</p>
<p>Since... | 36,146 |
<p><strong>The short question:</strong></p>
<p>Are there any studies of systems described by several hidden stochastic time dependent variables and observed variables that are given by known deterministic functions of hidden variables?</p>
<p><strong>More Details:</strong></p>
<p>I have a time dependent stochastic p... | 73,694 |
<p>I am doing a one-way ANOVA of a response variable (Y) on a treatment factor (T) of 7 levels. However, for each treatment, I have only 2 observations (or replicates). The ANOVA result shows the the means across the treatment are highly significant (p<0.001). I have check the normal and constant-variance assumption... | 36,148 |
<p>Which of the following is the correct code for fitting a GARCH-M(1,1) model where the ARMA(0,0) is "removed"? Or what is the correct code?</p>
<ol>
<li><p><code>modm11 = ugarchspec(variance.model=list(model="sGARCH", garchOrder=c(1,1)),
mean.model=list(archm=T, archpow=2, include.mean=F))</cod... | 73,695 |
<p>This seemed to me to be basic, but I can't seem to find a solution online, so I wondered what I might be missing.</p>
<p>I wish to include the output of an lm summary object inside an Sweave (.Rnw) document. I can either output the summary.lm as is, or use the xtable/Hmisc packages (through xtable or latex command... | 73,696 |
<p>I'm concerned with Box-Jenkins-models and especially the first step, the prewhitening to obtain meaningful crosscorrelations for identifying transfer functions and building regression models.</p>
<p>I'm working with SAS and here one has to identify a suitable ARIMA-model for the input series to achive white noise a... | 73,697 |
<p>I'm attempting to answer a general question about a method of musical comparision which is generalizable beyond western music but uses western music scales as a nearly sufficient subspace for dimensional reduction. What is a good probability model of the distribution of frequencies as represented by western sheet mu... | 73,698 |
<p>1)
Suppose, I have 25 sample values. I have no idea as to which distribution, the observation comes from. How will I proceed?</p>
<p>2)
With regard to the same question:
Suppose, though I have no idea, I pretend that it comes from normal distribution and estimate its mean and variance, do a P-P or an Anderson-Darli... | 73,699 |
<p>I have a random forests model with which I am trying to predict species presence or absence.<br>
This is my code:</p>
<pre><code>#read in dataframe containing observations of species presence/absence & predictor variables
mydata <- read.csv('mydata.csv')
#fit random forests model
fitmodelA <- randomFores... | 73,700 |
<p>I have a merged database from two cross-sectional surveys for distinct years ($t_1$ and $t_2$). If all questions were exactly the same, I could just stack the data horizontally and run a normal panel data OLS.</p>
<p>The problem is that some variables exist only for $t_1$, while other variables exist only for $t_2$... | 17,840 |
<p>I am implementing the ARIMAX model and need to implement feature selection. I have >100 features and a lot of data, so I need a method that isn't too computationally expensive. I tried a wrapper, backward feature selection algorithm but that was too expensive. Is there a less computationally expensive approach towar... | 37,223 |
<p>When running an OLS regression with a squared term,
$$
y = a + b_1(X) + b_2(X^2) + e
$$
I know that the partial effect of $X$ is $b_1 + 2b_2(\bar X)$ to get the overall effect of $X$ on $Y$ evaluated at the mean. Using</p>
<pre><code>reg y x c.x#c.x
margins, dydx(*) atmeans
</code></pre>
<p>does this in Stata and ... | 36,152 |
<p>I am working on classification of audio files. It is a binary classification and I plan to use SVM. I have used SVM before for face matching and other image analysis and retrieval stuff. </p>
<p>I have extracted the required feature vectors from the audio files, i.e., the training and test dataset and reduced their... | 73,701 |
<p>I have 5 years worth of mean wind speed meteorological data. I want to compare the observed wind speed data against a Weibull distribution on a graph of <strong>the probability density distribution.</strong></p>
<p>I have read about the different methods to find parameters $k$ (shape) and $c$ (scale) of a Weibull d... | 49,339 |
<p>Given an (infinite) data population from which you repeatedly draw samples of a fixed size. On each sample you learn a classifier which you then evaluate by computing the prediction error on a large independent test set.
The prediction error is defined as the average over all instances in the test set of the zero-o... | 73,702 |
<p>I am doing a project on sexual selection (male-male competition) in the turquoise killifish Nothobranchius furzeri. </p>
<p>There are two morphs of male in the population from which my fish are obtained from- one has a red tail and the other has a yellow tail. </p>
<p>My null hypothesis is: Tail colour is not rela... | 73,703 |
<p>How does a computer algorithm set up to take as input an arbirary bivariate probability density function, generate pairs of numbers from that distribution? I have found a routine called simcontour that is part of LearnBayes in R that performs that operation. </p> | 36,154 |
<p>I found a formula for pseudo $R^2$ in the book <a href="http://www.maths.bath.ac.uk/~jjf23/ELM/" rel="nofollow">Extending the Linear Model with R, Julian J. Faraway</a> (p. 59).</p>
<p>$$1-\frac{\text{ResidualDeviance}}{\text{NullDeviance}}$$. </p>
<p><strong>Is this a common formula for pseudo $R^2$ for GLMs?</st... | 73,704 |
<p>I am having trouble understanding the different estimators that can be used in an impact evaluation. I know that the intention-to-treat (ITT) estimator compares differences between eligible individuals without the program, and eligible individuals with the program, regardless of compliance. However, I thought the av... | 73,705 |
<p>I would like to find a reference, preferably free on the internet, where I can read about the theoretical or practical justification for the use of parametric / analytic probability distributions.</p>
<p>By parametric distributions I mean the named ones like Normal, Weibull, etc. </p> | 36,156 |
<p>I have a nested-case control study that I have been using for analysis. At the end of my work I have deduced a set of variables that I use later to to classify new cases. One example of a simple classifier I am using is a naive Bayes, which will output simply a probability. </p>
<p>So here is my question:</p>
<p>C... | 73,706 |
<p>I guess this means that omitting some variables in a certain interval, say, $(x_1, x_2, x_3, x_4, x_5) \to (x_1, x_5)$ in AR(4) model. </p>
<p>Is it right? Or does this means eliminating autocorrelations by adjusting autocorrealated variables by a certain method?</p>
<p>Thanks in advance!</p> | 73,707 |
<p>I would like to conduct a multivariate meta-analysis (multiple treatment arm meta analysis) comparing the effect of different drugs. My outcome measure is discrete and describes the number of occurrences of a specific side effect during the period of observation. The studies that i would like to include report the o... | 73,708 |
<p>I'm writing an essay on the effects of M&A announcements on stock prices. I understand most of the requirements perfectly fine, but I'm stumped on one particular part of the essay.</p>
<p>I have for every target and acquiror stock prices in the range [-170, 10] days, where day 0 is the announcement date. I use ... | 73,709 |
<p>I'm reading about convolutional neural networks. As I understood a feature map is a set of neurons (i.e like a single hidden layer in traditional ANN). So why feature maps are indexed by (i,j)? Shouldn't a feature map be indexed only by one index because it's just a set of neurons?</p>
<p>In the following picture l... | 36,160 |
<p>I am running into an error </p>
<pre><code>Error in node Y1[5]
Observed node inconsistent with unobserved parents at initialization
</code></pre>
<p>trying the following bugs model in JAGS accessed from R:</p>
<p>Apparently <code>Y1[5] = 2</code> causes problems in <code>dcat</code>. But I can't seem to figure o... | 37,450 |
<p>@Dmitrij Celov posted an answer to the question <a href="http://stats.stackexchange.com/questions/8303/how-to-do-logistic-regression-subset-selection">How to do logistic regression subset selection</a> saying that <a href="http://www.jstor.org/discover/10.2307/2531779?uid=3739256&uid=2&uid=4&sid=21102415... | 73,710 |
<p>I recently read the article "<a href="http://scholar.google.com/citations?view_op=view_citation&hl=de&user=TeaZX90AAAAJ&citation_for_view=TeaZX90AAAAJ%3ad1gkVwhDpl0C" rel="nofollow">Is It Really Robust?</a>" (Schmider, E., Ziegler M., Danay, E., Beyer, L. & Bühner M., 2010)
The authors of the articl... | 36,162 |
<p>I have near about 50 files(each file corresponds to a patient) with 4 columns -</p>
<pre>chromosome start.position stop.pos value</pre>
<p>First 3 columns in all 50 files are same and fourth column is value which is different (or can be same for some) for all patients. Basically this value correspo... | 36,163 |
<p><em>(Apologies for the ASCII tables, Stackexchange doesn't allow HTML tables and since I'm not supposed to link to an image, this is the only way I know of showing the data)</em></p>
<p>I'm learning about ANOVA F-testing and stumbled upon this problem:</p>
<p>There exists the following set of data regarding four t... | 73,711 |
<p>Imagine picking a 1 when any real number is equally likely. What is the pdf? Does this idea have a known use? What is its name?</p>
<p>There could be a use for a uniform random real number. It could end up always being integrated. It could be a prior for a number that is completely unknown. </p>
<p>It would ... | 36,164 |
<p>I am just wondering what kind of things could cause power to be lost in general (the opposite of reducing the noise of the data to increase the power of the test). </p>
<p>Could anyone give some summary or ideas how to think of the power issue?</p> | 30,010 |
<p>I am working on a business research paper. The hypothesis is that the sales rep influences the customer's decisions. Independent variables consist of the sales rep's: knowledge, pushiness, friendliness, etc. Dependent variable is the customer's willingess to buy.
In all, I have 12 questions that I asked on a Likert... | 36,166 |
<p>For homework I have been given a 20-dimensional input $x \in \mathbb{R}^{20}$, many of which are suspected to be irrelevant. I tried using L1-norm Lasso regularization to uncover which dimensions contribute to the output: </p>
<p>$$L(\beta) = \sum_{i=1}^n (y_i - \phi(x_i)^T \cdot \beta)^2 + \lambda \sum_{j = 1}^k l... | 36,167 |
<p>We recently studied a model with a likelihood function of the form</p>
<p>$$\Pr(d_i|\omega,t_i)=(1-d_i)+(2d_i-1)\cos^2(\omega t_i),$$</p>
<p>where $d_i\in\{0,1\}$, $\omega$ is an estimation parameter, and $t_i$ are determined by the experimenter. This is a set of independent but non-identically distributed Bernou... | 36,168 |
<p>my project is identification of factors influencing motor bikes for home to office trip. there are some attiributes like gender,age,marital status,education qualification,job type,working sector, no. of members in household,working members in household,monthly income,total household income,no. of motor bikes,members... | 36,169 |
<p>For the lasso problem
$\min_\beta (Y-X\beta)^T(Y-X\beta)$ such that $\|\beta\|_1 \leq t$. I often see the soft-thresholding result
$$ \beta_j^{\text{lasso}}= \mathrm{sgn}(\beta^{\text{LS}}_j)(|\beta_j^{\text{LS}}|-\gamma)^+ $$
for the orthonormal $X$ case. It is claimed that the solution can be "easily shown" to be... | 73,712 |
<p>I have worked out a naive approach for clustering different variables, and I wonder what better approaches are there. I have data with many more dimensions (variables) than observations (samples), and I wish to cluster the variables by their correlation. However, the observations correspond to different groups, for ... | 73,713 |
<p>I remember once in our Statistics class, our professor mentioned an interesting problem, that is:</p>
<blockquote>
<p>In our class, consisting of 30 students, I bet that there are two students born on an exact day of year.</p>
</blockquote>
<p>It was quite clear to all of us that he will lose the bet, but then h... | 49,922 |
<p>I have just started learning these things, and I would really appreciate any help on this.
There are 4 nodes in a network (say $A,B,C,D$), and each node has certain failure probabilities, namely ${\rm Pr}(F_A)$, ${\rm Pr}(F_B)$, ${\rm Pr}(F_C)$, ${\rm Pr}(F_D)$.
Then, I have a $4 \times 4$ correlation Matrix which c... | 73,714 |
<p><img src="http://i.stack.imgur.com/gVwaj.png" alt="Probability plot of standardized residuals."></p>
<p>I go to Stat from main menu then Regression -> Regression...</p>
<p>Although I have selected almost everything I cannot plot the extra info (p-value, mean, N, etc ) above in circle. I use Minitab 16.2.0.</p> | 30,051 |
<p>I recently became interested in <em>Cognitive Diagnosis Modelling</em>, which classifies respondents to skill profiles based on their responses and a hypothesized relation between skills and items (Q- or Transfer-Matrix).</p>
<p>I had a look at at <a href="https://pslcdatashop.web.cmu.edu/" rel="nofollow">https://p... | 73,715 |
<p>In a linear mixed model, you take the covariance between data into account by adding a random intercept per cluster.</p>
<p>For example, you measure the effect of a drug campaign over time on students, and add a random intercept per school and a random intercept per student within a school:</p>
<p>$Y_{ijk}=\beta_{... | 73,716 |
<p>According to Bayes' theorem, $P(y|\theta)P(\theta) = P(\theta|y)P(y)$. But according to my econometric text, it says that $P(\theta|y) \propto P(y|\theta)P(\theta)$. Why is it like this? I don't get why $P(y)$ is ignored. </p> | 73,717 |
<p>Some authors eg Hunter et al (1982) propose that we must correct sample correlations for the measurement error.It seems measurement error need not be corrected for when we take a recourse to the meta-analysis of sample-correlations In a meta-analytic perspective, measurement error(here it is construct bias) has a li... | 73,718 |
<p>We just started learning asymptotic theory, and to prove the lindberg-levy central limit theorem, weak law of large numbers etc, we 'scale and standardize' the RVs so it ends up having a standard normal distribution when sample size T tends to $\infty$. The math behind it is straightforward but can someone give a qu... | 36,178 |
<p>I am looking for different types of regression models for such data in which the dependent variable is always decreasing with the independent variables.</p>
<p>The two's, I know and have used so for are</p>
<pre><code>Y = C + C_a A + C_b B
</code></pre>
<p>and </p>
<pre><code>Y = C + C_a A + C_b B + C_a2 A^2 + C... | 73,719 |
<p><strong>Figure A</strong> demonstrates a point process (object=rectangle) with marks as the length and width of the rectangle. <strong>Figure B</strong> shows a realization of the point process regarding the information extracted from the input data.<br>
The <strong>question</strong> is:<br>
How to condition (using ... | 73,720 |
<p>I want to make a linear regression where the dependent variable is the amount spent on some good and the independent variables are some characteristics of the consumer (age, gender, wage, etc). Specifically, I want to know how much this characteristics influence the annual spending on this good. </p>
<p>But the way... | 73,721 |
<p>I have a data set consisting of 166 observations on 24 variables (<code>a1</code>, <code>a2</code>, <code>a3</code>, <code>a4</code>, <code>b1</code>, ..., <code>b4</code>, ..., <code>f4</code>). Responses where made on a 6-point scale from 1 to 6:</p>
<pre><code>d <- read.table("http://pastebin.com/raw.php?i=m1... | 73,722 |
<p><strong>Simulated Annealing</strong> is a method of simulation in which each entity in the system is perturbed in some characteristics e.g., location due to increasing and decreasing the heat (the energy) of the entire system.<br>
My question is about the application of simulated annealing approach to conditioning s... | 73,723 |
<p>Our professor keeps on writing in his slides that when you test different ARIMA models on your time series, one always has to keep T fixed.</p>
<p>I assume he is talking about fitting your model using the same number of observations. If you try a model with a higher lag, you loose one observation to fit the data on... | 36,181 |
<p>So, some algorithms were motivated by theoretical work, such as in the case of boosting.
Adaboost was introduced as an <a href="http://www.face-rec.org/algorithms/Boosting-Ensemble/decision-theoretic_generalization.pdf" rel="nofollow">algorithm for solving</a> the <a href="http://www.cs.princeton.edu/~schapire/paper... | 73,724 |
<p>X,Y are independent random variables.
X's pdf = f(x)
Y's pdf = g(x)
if Z= X+Y
what is the Z's pdf?
Can it be calculated?</p> | 36,182 |
<p>I want to measure the inner correlation of the occurrences of events i.e. I want to distinguish between the two (drawn) and say "in the second sample events occur more conglomerate compared to the first":</p>
<p><img src="http://i.stack.imgur.com/NxRBP.png" alt="enter image description here"></p>
<p>Isn't this dif... | 36,184 |
<p>I have a microarray data which I ran through a continuous covariate (say "X"). I did this using 4 different methods.</p>
<p>For the results obtained from each of the 4 methods, I have the following from each of the 4:</p>
<ol>
<li>p-value, </li>
<li>FDR significant value, </li>
<li>"Bonferonni significance" (sayin... | 43,114 |
<p>I want to check various classification model like random forest, tree, knn,etc. I used some bench marking data set but now I need to simulate my own data set with a binary response variable.</p> | 73,725 |
<p>According to <a href="http://blog.gribblelab.org/2009/03/09/repeated-measures-anova-using-r/" rel="nofollow">this post</a> the best way to do post hoc analysis in ANOVA in R is t-test + ptukey. Because lme + glht "essentially assumes the sphericity assumption holds".</p>
<p>How are t-test + ptukey "concerned about ... | 73,726 |
<p>I have a problem with this exercise in probability and statistics:
Calculate the probability density function (PDF) of
$$Z=X+Y$$
where $Y$ is discrete random variable which is equal to $-1$ and $1$ with equal probability;
$X$ is a standard gaussian random variable independent of $Y$.</p>
<p>I know that the PDF of ... | 73,727 |
<p>I am having trouble understanding the plot below (taken from <a href="http://blog.echen.me/2012/03/20/infinite-mixture-models-with-nonparametric-bayes-and-the-dirichlet-process/" rel="nofollow">Edwin Chen's blog</a>). </p>
<ul>
<li>What is the <strong>x-axis</strong> supposed to represent? Shouldn't color be a cate... | 73,728 |
<p><a href="http://en.wikipedia.org/wiki/Factorial_experiment" rel="nofollow">Factorial experiments</a> have several advantages when one wants to examine the effect of several independent variables (factors) on an outcome. Perhaps most importantly, they often allow additional factors without major increases in sample s... | 73,729 |
<p>If you're training a model using cross validation on one set of data, and then you're scoring that model on a separate set of data, is it advised to score, say, 1000 times on subsets of your data? </p>
<p>I'm thinking taking bootstrap samples or something, and then scoring the model, then another boot strap, etc. ... | 73,730 |
<p>Suppose $U, W, V, S$ are four independent normal random variables with mean $0$ and variance $1$. Let $X=W+U$, $Y=2W+S$, $Z=3W+V$. What is $f(X, Y, Z)$?</p>
<p>Thanks!</p> | 47,733 |
<p>I was wondering if any of you could help me understand the response I got from this clustering algorithm (Metis). As you probably can see, I'm trying to cluster IP addresses based on common records accessed. The graph file contains one node per IP, and weighted edges, where the weight is equal to the number of commo... | 73,731 |
<p>I am analyzing data from an experiment in which treatment levels increase quadratically, e.g. the treatment levels are $0, 1, 4, 9$.</p>
<p>When analyzing the response using regression, would it make sense to use the square root of the treatment level as a predictor? </p>
<p>If so, how would this affect interpreta... | 36,188 |
<p>I really enjoy this resource -- its been super helpful to learn and read along as I explore some concepts for a new venture. But now I need real help -- in the short term contract, and in the long term statistical pros. What are the best sites were folks look for side projects and gigs? What is the best advice you ... | 73,732 |
<p>I am exploring different classification methods for a project I am working on, and am interested in trying Random Forests. I am trying to educate myself as I go along, and would appreciate any help provided by the CV community.</p>
<p>I have split my data into training/test sets. From experimentation with random fo... | 73,733 |
<p>(Apologies if the notations are "unusual", I'm not sure what the correct notations should be. I'm putting an example at the end of the question.)</p>
<p>Let's assume there was an initial dataset of an n by m matrix $M=(x_{ij})$ with $1<=i<=n$ and $1<=j<=m$, from which the following two vectors have been... | 73,734 |
<p>I'm having problems understanding the concept of a random variable as a function. I understand the mechanics (I think) but I do not understand the motivation...</p>
<p>Say $(\Omega, B, P) $ is a probability triple, where $\Omega = [0,1]$, $B$ is the borel-$\sigma$-algebra on that interval and $P$ is the regular le... | 36,192 |
<p>I was wondering if you can share your experiences on what you feel is the best method to test lead / lag relationships between I(1) time series variables (i.e stock prices) and advantages and disadvantages of your proposed method(s). Also if you have links to academic papers that further describe these methods I wou... | 73,735 |
<p>I am sitting on a pile of data concerning wages at a local company and other information, such as the gender, whether the person in question belongs to a minority group etc. What I would like to investigate is whether an additional year of education gives the same relative increase in wages for lower and higher educ... | 36,193 |
<p>I would like to calculate the value of bacteria on 4 surfaces $i=\{1..4\}$. A person touches some of those 4 surfaces at random and a count is made on their finger after each surface contact ($x_i$). </p>
<p>Someone lost the bacteria count ($x_i$) after each surface but I do know the total count (X) on a persons's ... | 36,194 |
<p>I have set of 16 questions that have been answered on a numerical scale, from 1 to 7. They are answered by 200 couples, and I want to show there is a difference in the answers on gender. On a casual glance at the data, I see there is little difference between the genders for 6 of the questions, but is for the other.... | 73,736 |
<p>We have a potential biomarker for predicting whether a patient has cancer or not. The biomarker test result is binary being positive or negative. We want to get some sense of the amount of patients that need to be tested to determine whether this biomarker is a good predictor or not.</p>
<p>From reading on the int... | 36,196 |
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