question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p><a href="https://gist.github.com/1370032" rel="nofollow">This R code</a> simulates Gaussian mixed effects data with one random effect and one fixed effect. How would I modify that code to simulate Binomial mixed effects data with one random effect and one fixed effect? </p> | g21176 | [
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<p>If I am looking at an <code>ivreg2</code> equation where:</p>
<pre><code>ivreg2 y1 x2 x3 x4 (x1 = x5 x6)
</code></pre>
<p>and I know that <code>x5</code> and <code>x6</code> are endogenous variables (i.e. they are motivated by latent, unmeasurable characteristics) and there are no other viable alternatives, does I... | g63484 | [
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<p>I have the following statistical problem:</p>
<p>I have two boxes, each has exactly 10000 numbers in it. Each number is either 0, 1, or 3. What I need to know is if the average amount in one box is bigger or smaller than the average amount in the other box.</p>
<p>Unfortunately, picking numbers is very costly for ... | g63485 | [
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<p>Say I have multiple tests on N data points, for each I get a p-value ($0 < p < 1$).
If the null hypothesis is true, I would expect that the distribution of p-value to be uniform. If, however the empiric CDF is larger than the uniform diagonal ($\text{CDF}(p) > p$), e.g. there are 0.1 fraction of samples wit... | g63486 | [
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<p>Is there an R package that I can use to explore whether there exist relationships between variables?</p>
<p>Typically when I am looking for patterns I look at correlations, and then a facet plot. Then I manually apply some transformations to variables in the data. I was wondering if I could accelerate this process ... | g63487 | [
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<p>I'm very new to the concept of data mining. My background is from statistics in the social sciences, and my familiarity in the computer sciences is small.</p>
<p>Based on what I have read so far, it appears that data mining looks at "Big Data," and then uses a computer program to run lots of regressions/correlation... | g21181 | [
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<p>If we have a long, high resolution time series, with lots of noise, it often makes sense to aggregate the data to a lower resolution (say, daily to monthly values) to get a better understanding of what's going on, effectively removing some of the noise.</p>
<p>I've seen at least one paper that then applies some sta... | g63488 | [
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<p>I have a longitudinal data with multiple time points (measured twice every year). There was seasonal difference on the outcome variable of interest (BMIz) if using mixed model (where time points were nested within kids, and kids were nested within schools). </p>
<p>I also calculated the percentages of children tran... | g63489 | [
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<p>I understand that in the one sample case, z is employed where population variance is known and t for where it is unknown. </p>
<p>In the <strong>two sample case</strong>: we are trying to test $H_0: \mu_x=\mu_y$ against $H_1: \mu_x\not= \mu_y$, for finite variance; $\sigma^2_x$ and $\sigma^2_y$; while $n_x$ and $n_... | g63490 | [
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<p>How do you know when deseasonalization is not necessary? That is, from what I understand, if you want to just look at the trend and irregular components of a time series, then you just need to remove the seasonal component. However, let's say we're working with an irregular time series that is not affected by season... | g41576 | [
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<p>Apologies in advance, time series is not my strength.</p>
<p>Say I want to predict f(T+1) using f(T-1, T-2, ..., T-N) -- for example using a multi-level preceptron. </p>
<p>If I want to enhance this using some other signals say using weather data on times T-1, T2, ..., T-N</p>
<p>Would this still be considered Ti... | g63491 | [
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<p>In Gelman and Hill 2007 (<a href="http://www.stat.columbia.edu/~gelman/arm/" rel="nofollow">http://www.stat.columbia.edu/~gelman/arm/</a>), they mention that adding an $\epsilon \sim N(0,\sigma^2)$ term to a Poisson regression can be used to account for overdispersion. </p>
<p>On a number of different sites I've se... | g10371 | [
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<p>I want to fit a 1-parameter IRT model on a questionaire with 15 questions and about six million people. Considering the large N, standard errors aren't essential. It looks like the IRT world is sort of dizzying, and I was wondering if there were any tips as for what the proper software approach would be. </p> | g37951 | [
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<p>Ok, I'm having trouble with standard error, sampling distributions and confidence intervals.</p>
<p>The question I am trying to answer is: How many holes do I have to drill in the ground to get good idea of the fracture density (# of fractures / hole).</p>
<p>I simulated a computer model with theoretical fractures... | g63492 | [
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<p>I'm considering a two-part, member-level model for predicting Year 2 inpatient health care costs based on health care utilization, demographics, and diagnosis data from Year 1. A logistic regression to predict Year 2 inpatient utilization (yes/no) + a loglinear OLS to predict Year 2 log cost (with perhaps a Duan Sme... | g21188 | [
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<p>What are the odds of the following:</p>
<p>Great Grandmother was born <code>January 14 (1/14)</code></p>
<p>My Grandfather was born <code>April 11 (4/11)</code></p>
<p>I was born on <code>January 14 (1/14)</code></p>
<p>My son was born on <code>April 11 (4/11)</code> </p>
<p>FYI: My Great GrandMother lived to b... | g21189 | [
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<p>I am learning Maximum likelihood estimators for a inference class. And this is a problem I came across.</p>
<p>Let $X_1,X_2,X_3,\ldots, X_n$ be a random sample with p.m.f $$p(X)=\theta(1-\theta)^x; x=0,1,2,\ldots\quad \mathrm{and}\quad 0<\theta<1$$.<br>
As maximum Likelihood estimator I obtained $\hat{\theta... | g63493 | [
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<p>I am comparing two medical imaging analysis techniques, and I would like to assess the inter- and intra-rater reliability for using each method. I am planning the study design, and would like help with finding an appropriate statistical analysis method. A description of the analysis techniques follows: </p>
<p>For ... | g63494 | [
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<p>I have many categorical and numerical features and I sub-selected a few of them by a Random Forest. Now I'd like to determine which features probabilistically(/causally?) explain the target. Something that I can tell to business people which isn't a black box like a Random Forest.</p>
<p>I can plot the class densit... | g63495 | [
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<p>Say I have two random variables, X and Y. Their joint probability density function is a uniform distribution inside the triangle with vertices at (0,0), (0,1) and (1,2). The area is 1 so the joint pdf is 1. Calculating the marginal cumulative distribution function I get P_X = x^2 and P_Y = y - (y/2)^2. The question ... | g63496 | [
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<p>According to my notes, in a statistical model where </p>
<p>$$Y_i=\beta_0 + \beta_1(x) + u$$</p>
<p>(where $u$ is the error term) the predicted slope is $$\hat{\beta}_1 = \frac{\operatorname{Cov}(X, y)}{\operatorname{Var}(X)}$$
According to this Khan academy <a href="http://youtu.be/8RSTQl0bQuw?t=3m40s" rel="nofol... | g63497 | [
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<p>I am working on social influence based on frequency, meaning if a person repeatedly appears at a location many times then he/she is more influential at that location. In other words, he/she can influence other people at that location with a higher chance of success compared to someone who is not there often.</p>
<p... | g21191 | [
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<p><br><br>
I am using the function <code>svm</code> from the package <code>e1071</code> in <code>R</code> to generate a support vector machine model. I have a <b>very large</b> data set, and for the moment, while in an exploratory mode, want to simply read in small slices of the data that can be modeled on my single ... | g63498 | [
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<p>I'll try and explain where I am getting stuck.</p>
<p>I wish to model delay to treatment. I observe patients nested in hospitals. I have a mixture of patient and hospital level covariates. I suspect that there are unmeasured covariates that induce correlation between patients being treated in the same hospital. Thi... | g63499 | [
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<p>I'm looking at the change in vote shares for an election between two periods. I'd like to say something about the contribution of one variable in particular towards the election swing I document. I'm wondering if there is a standard approach in the literature.
I'd like to be able to say something like X accounts for... | g63500 | [
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<p>So I am looking at whether the effect of rainfall on crop yield for 8 different States is similar across these States i.e. I am testing whether the slopes between rainfall and yield is significantly different from each other among the eight States. For each State, I have yield and rain data for 48 years. I ran the f... | g21195 | [
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<p>I have a small doubt. My real data looks like this</p>
<p>Y values are random values of integers from 0 to 2000. X values run like 1,2,3,4,5,.. to 2 million.</p>
<p>Now, my task is to identify significant peaks and remove background noise.</p>
<p>To achieve this , I used 2 methods :</p>
<p>I created a sliding wi... | g63501 | [
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<p>Conceptually, I don't understand what is a least angle regression and why it solves LASSO</p>
<p><a href="http://www.cc.gatech.edu/~isbell/reading/papers/lasso_simple.html.pdf" rel="nofollow">http://www.cc.gatech.edu/~isbell/reading/papers/lasso_simple.html.pdf</a></p>
<p>We know that LASSO is </p>
<p>$$\min_x||A... | g12247 | [
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<p>I am analyzing marketing data and Y response are as follows. There are 2 different binary Y columns. Each row of the data has data about a customer and what he bought</p>
<pre><code>a customer bought product A - Yes or No
a customer bought product B - Yes or No
</code></pre>
<p>In order to build a decision tree, ... | g63502 | [
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<p>I've just started working with the GLM negative binomial and I was wondering if it's possible to carry out a leave-one-out cross-validation for negative binomial GLM as I'm having troubles doing it with R using {boot}. My variables are standardized!Can it be a problem?
Any help will be very very appreciated! Sorry i... | g63503 | [
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<p>My goal is to fit a custom logistic regression/survival analysis function using the <code>optim</code>/<code>maxBFGS</code> functions in R and literally defining the functions by hand and then extracting the betas.</p>
<p>I was always under the impression that for the packages <code>speedglm</code>, <code>biglm</co... | g63504 | [
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<p>There is one other question similar to mine (<a href="http://stats.stackexchange.com/questions/41182/compare-independent-numeric-vectors-means-in-r">Compare independent numeric vectors (means) in R</a>), but has not been answered (1 year has passed), so I'm repeating the question here.</p>
<p>I have obtained exam s... | g63505 | [
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<p>Basic statistics courses often suggest using a normal distribution to estimate the mean of a population parameter when the sample size <em>n</em> is large (typically over 30 or 50). Student's T-distribution is used for smaller sample sizes to account for the uncertainty in the standard deviation of the sample. When ... | g63506 | [
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<p>I have 11 variables in my data set.<br>
farmers Group(1,2,3,4 this is my dependent variable)</p>
<p>Independent variables<br>
Total holding ,Crop area , barn capacity.....and barn capacity extent match and YPH.<br>
These last 2 variables are calculated using the existing explanatory variables in the data set(e.g. Y... | g63507 | [
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<p>I am running a binomial mixed effects logistic regression in R using <code>glmer</code> for a sociolinguistics project. I was asked to used deviation (effect) coding. From what I gather, in deviation coding the last level in a factor is assigned -1, because this is the level that is never compared to the other level... | g63508 | [
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<p><a href="http://www.amazon.co.uk/McGraw-Hills-500-Statistics-Questions-ebook/dp/B00EHIEDVS/ref=sr_1_1?ie=UTF8&qid=1391981126&sr=8-1&keywords=500%20statistics%20questions" rel="nofollow">This book</a> gives 500 question and answers on introductory statistics.</p>
<p>Are there any books out there which gi... | g63509 | [
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<p>Suppose we have a task that can be a success or a failure. We pay a fee and get a success for any attempt at the task.
We can pay more in order to get a higher success rate. Given sufficient resources, we can guarantee success. For my example this shows the percentage success (i.e. probability of success on any atte... | g40939 | [
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<p>So I have N=147 control time-series signals and N=134 treatment (THC) signals. I want to compare if there are any significant differences in frequency power in the two groups. </p>
<p>The top part of the figure below shows the median frequency power for each frequency of the two groups. </p>
<p>Thus for each frequ... | g13710 | [
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<p>In their book "Robust Statistics", Maronna et al. consider the following model for robust regression: $y_i = \beta x_i + u_i$, where $u_i$ are independent of the $x_i$, and are i.i.d, with finite variance. They go on to provide a robust estimate $\hat{\beta}$ of $\beta$ which is asymptotically normal and give the co... | g63510 | [
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<p>When we perform experiments (on small sample sizes (usually the sample size per treatment group is about 7~8)) on two groups, we use a t-test to test for difference. However, when we perform an ANOVA (obviously for more than two groups), we use something along the lines of Bonferroni (LSD/# of pairwise comparisons) ... | g15396 | [
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<p>I'm a first year postdoc in pure mathematics (geometry/topology with strong background in analysis) with undergraduate statistics and probability background (with also measure theoretic probability). I also have some programming knowledge in ForTran, C and Matlab, but I never used them in my pure mathematics career ... | g21207 | [
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<p>Correcting exams is probably the most boring task of a teacher.</p>
<p>But it might be amusing for us to collect funny statistics exam answers.</p>
<p>One entry per answer. </p> | g40512 | [
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<p>I am seeing some promising results with this method for my 'nutrition' dataset but am wary about modelling on results of a model.</p>
<p><strong>Problenms with this data</strong>
I cannot seem to reduce my many correlated variables in a way that is acceptable.
-PCA factorises the variables and indeed does successf... | g63511 | [
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<p>I found similar topic but it dealt with the question whether it's better to discretize numerical dependent variable or leave it as it is.
I'd like to find out what are your experiences with training decision trees using continous explanatory variables. Is it better to convert them to categorical/ordinal values? If ... | g49675 | [
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<p>I am interested - mostly just for my own knowledge, and not for any real problem - in the use of weighted least squares to estimate a model on individual-level data and aggregated versions of those same data. Here's some simple R code to show what I'm talking about. Basically, I estimate a regression model <code>lm1... | g63512 | [
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<p>I need to classify URLs into categories. Say I have 15 categories that I'm planning to zero down every URL to. </p>
<p>Is a 15-way classifier better? Where I have 15 labels and generate features for each data point. </p>
<p>Or building 15 binary classifiers, say: Movie or Non-Movie, and use the numbers I get from ... | g63513 | [
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<p>Disclaimer: I have a very minimal stats background and am just getting into this stuff. Corrections to any terminology I use or an improved rephrasing would be super appreciated.</p>
<p>I have a simple science/perception experiment that I've run, testing a single group of subjects on 2-dimensions of conditions: spe... | g63514 | [
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<p>For which distributions x, other than beta, is the x-binomial distribution nice? The beta and binomial distributions are famously conjugate but I am curious if other non-conjugate distributions will give comparably simple compound pmfs. By nice I mean that the pmf is nice to compute without resorting to numerical ... | g40978 | [
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<p>Suppose $X$ is non-central exponentially distributed with location $k$ and rate $\lambda$. Then, what is $E(\log(X))$.</p>
<p>I know that for $k=0$, the answer is $-\log(\lambda) - \gamma$ where $\gamma$ is the Euler-Mascheroni constant. What about when $k > 0$?</p> | g63515 | [
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<p>I want to build a standard topic classifier. I was told gensim is the way to do it. I have difficulty training the gensim system. How do we provide a training data in a fast way. Some forum suggested Wikipedia training, and I used it. But the code
WikiCorpus('....en.bz2')
is running since last 6 days with no resul... | g63516 | [
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<p>I'm trying to figure out what is the most appropriate statistic test for use with my data and was hoping for some advice.</p>
<p>The primary data consists of a binary independent variable (patient test - positive or negative; there are some missing values which are being excluded for now) for which we want to deter... | g63517 | [
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<p>Say you are given two multivariate data sets, say an old one and a new one, and that they are supposed to have been generated by the same process(that you have no model for) but perhaps, somewhere along the line of collecting/creating the data, something went awry. You wouldn't want to use the new data as, say, a va... | g37431 | [
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<p>I have been running a regression analysis in SPSS where my dependent variable is a composite. By this I mean that it is built up of 7 different items. How can I make it one dependent variable? Because in SPSS you have to give only one dependent variable but I have 7 items for one dependent variable. Is there a way t... | g63518 | [
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<p>I know how to plot confidence intervals (CI) to a plot based on their values, but I'm not sure if there's a proper way to plot CI on a plot based on fraction above/below; e.g.</p>
<pre><code>#dummy data
d1=c(20,30,50,80,70,40,4,7,9,11,14)
d2=c(22,32,51,90,100,30,14,71,19,12,1)
data=list(d1,d2)
#calculating the frac... | g63519 | [
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<p>I have survey data from approximately 500 companies, and on one question they were asked to rate their priorities from 1 to 8. It's a forced ranking so you can't answer with two 8s. The issue that I'm now facing is to make some logical groupings or of the companies analysis. </p>
<p>What are typical strategies for ... | g63520 | [
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<p>I am reading <a href="http://rads.stackoverflow.com/amzn/click/0521284147" rel="nofollow">Judgement under Uncerntainty</a> and in p.65 it is stated that in the normal linear model, correlation of input variables decreases the predictive accuracy (in contrast to the human perception which is exactly the opposite). I ... | g21218 | [
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<p>I'm trying to estimate the predicted probabilities of an observation being a particular integer, $y$, after a negative binomial regression model. Long's <em>Regression models for categorical and limited dependent variables</em> gives this predicted probability as (pg.237):</p>
<p>$$
\hat{\text{Pr}}(y \mid x) = \fra... | g21220 | [
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<p>A child must learn a poem by heart. The poem has 200 lines. To test the child, the teacher asks the child to complete ten lines of the poem given the first half of the sentence. If the child gets, say, seven lines correct, the teacher assumes that the child knows 140 lines of the poem correctly.</p>
<p>What is the ... | g21221 | [
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<p>I have recently learnt about kernels in machine learning. And I have been introduced to many different processes e.g. Gaussian process, Wiener process. Now my question is why a set of functions has been named as a process? For example this is the definition of Gaussian process:</p>
<p>Let $\mu: X \to R$ be any func... | g63521 | [
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<p>Suppose one has a deck of cards. If one reshuffles it using a discrete probability model (based on combinatorics) one will still have the same probability of getting a particular card on each draw.</p>
<p>This seems to be a little bit naïve for real cards, since reshuffling is somewhat non-random. Suppose you know ... | g63522 | [
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<p>While drawing graphs that compare the silhouette measure of different clustering algorithms, what unit should I specify for the silhouette width?</p> | g40534 | [
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<p>I have a history of purchases from different clients and I'm trying to calculate a threshold in days after which the probability of the client making another purchase is below 50% (asumming that this means that it's more improbable for him to purchase again).</p>
<p>My current approach was to create an histogram wi... | g21223 | [
-0.006115555297583342,
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0.0029729625675827265,
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0.051156166940927505,
0.07535836100578308,
... |
<p>I'm using <code>glmnet</code> package to learn regression models,it works fine, but for some models, I face an error and my script stops running.</p>
<p>Here is my effort:</p>
<pre><code># goal : build a model for every row of T
# T: matrix
#MI: matrix feature matrix
model <- vector("list", nrow(T))
for(i in 1... | g21224 | [
0.014940188266336918,
-0.030750980600714684,
0.00009859077545115724,
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0.06835301220417023,
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0.029397107660770416,
-0.020722994580864906,
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-0.059167563915252686,
0.01544763520359993,
0.06121670454740524,
0.01617005653679371,
0... |
<p>I am curious that why in CFA model, observed measures operate as dependent variables.
In my understanding, observed measures served as data point that estimating other parameters, such as latent variables and errors.</p>
<p>Thanks,</p> | g63523 | [
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0.004933866206556559,
0.004560547880828381,
0.0... |
<p>in the formula for t test, t = (mean1 - mean2)/sqrt[(var1 + var2)/N]</p>
<ol>
<li><p>is N the total number of subjects in both groups being compared or the number of subjects in each group or condition?</p></li>
<li><p>df = N-2
is N the total number of subjects in both groups being compared or the number of subjec... | g63524 | [
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... |
<p>I was reading through <a href="https://github.com/jpfrench81/files/raw/master/changepoint.pdf" rel="nofollow">this</a> one page paper on using Gibbs sampling for detecting a change point in a time series like data. While I understand the part where the $\lambda$ and $\phi$ are chosen from a gamma distribution I do n... | g63525 | [
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0.031279683113098145,
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0.0739421620965004,
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0.00... |
<p>I'm wondering what distribution results in adding two (or more) type-one Pareto distributions of the form $x^{-\alpha}$. Experimentally, it looks like a two-mode power-law, asymptotic to the difference of alphas.</p> | g63526 | [
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<p>I am computing the MLE values of some parameters of a likelihood function, subject to non-negativity constraints. Given these constraints, some of the MLE values for my parameters are exactly in the boundary (i.e. they are equal to zero). Is it still valid to estimate the variance of the MLEs using the Hessian of th... | g21227 | [
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<p>I am interested in estimating an endogenous treatment effects model of the following form:
\begin{eqnarray}
Y_i = \alpha + \beta_x X_i + \beta_{z1} Z_{1i} + e_i \\
X_i = a + \beta_{z2} Z_{2i} + v_i
\end{eqnarray}
where $Y$ is a continuous variable, $X$ is a binary variable that is endogenous in the first equation a... | g63527 | [
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... |
<p>Please consider this data set:</p>
<pre><code>y <- c(2, 4, 6)
x <- c(1, 2, 3)
</code></pre>
<p>Now calculate a linear model using lmp():</p>
<pre><code>library(lmPerm)
lmp(y ~ x)
</code></pre>
<p>What I get, but don't understand, is this:</p>
<pre><code>Coefficients:
(Intercept) x
... | g63528 | [
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-0.... |
<p>I am currently working with quantitative data in the form of user-provided keywords which means the same idea can be expressed differently (e.g. "teachers, teaching, university, students" are related to the same "Education" subject area).</p>
<p>I am currently using excel which is totally inadequate as Excel is inc... | g63529 | [
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<p>I am programming an ARIMA model. The MA part of the model uses past forecast errors. How do I calculate these errors? Should I use any other model?</p> | g500 | [
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0.024015583097934723,
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<p>I want to test a model using discriminant function analysis. My question, as the title states, is very basic: <em>What is a discriminant function?</em> That is, how can I interpret the different discriminant functions?</p>
<p>I'll briefly explain this question. I have several continuous variables, and a categorical... | g21234 | [
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... |
<p>I have a pair of data sets, and I want to know whether the medians of these two sets differ significantly. I've calculated the median of each set and subtracted them from each other. How can I determine appropriate error bars for that point?</p>
<p>I was thinking I would take the median absolute deviation (MAD) of ... | g63530 | [
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<p>I'm currently doing a modelling project. However, I haven't taken a bunch of statistics classes, so I have to teach myself generalized linear models. I'm reading <em>Generalized Linear Models for Insurance Data</em> (Heller and de Jong, 2008, CUP), and I have two questions:</p>
<p>1. On page 64, it says: </p>
<blo... | g63531 | [
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<p>I am investigating the effect of genomic dysmethylation on cancer survival time, with data from multiple different cancers with very different survival curves. </p>
<p>Normally, I would split the cases into high and low dysmethylation, and do a log-rank test on the Kaplan-Meier curves. This isn't possible because f... | g63532 | [
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<p>I have heard of the "<strong>false discovery rate curve</strong>" (e.g <a href="http://people.inf.ethz.ch/bkay/publications/Brodersen_2010a_ICPR.pdf" rel="nofollow">here</a>) but never seen an example.</p>
<p>If I recall correctly from a conversation with a colleague, the <code>y-axis</code> in the FDR curve measur... | g21236 | [
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<p>I'm using ANOVA to test for differences between different values of the same factor for a mixed effects model which I produced. My model is: <code>m2 <- lmer (ovsize ~ d.sheetratio + (1|nid), REML=FALSE)</code>.
Following this, I subsetted the data so that each separate model described just data values for just o... | g642 | [
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<p>I have already used the logit transform on my outcome variables (which are displayed in percentages). However, this obviously gives me -INF values and since my data includes a lot of zeros in some instances, this makes it hard to analyse. </p>
<p>I have now tried an empirical logit transform, adding the smallest no... | g63533 | [
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0.014825460501015186,
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... |
<p>I am running a multiple regression looking at whether TV viewing predicts waist circumference (WC). When I ran through the tests with my tutor we placed WC as the dependant and TV as independent, then ran it again with some of the potential confounders. However, the TV variable is ordinal (1- never, 2- 0 to 59 mins,... | g21237 | [
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0.03517016023397446,
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0.... |
<p>I want to estimate parameters of VARMA model using maximum likelihood estimation using real data. The problem I face with is that I don't know how to set the initial values for the parameters. I tried to choose randomly but the objective function is always undefined at initial point.</p>
<p>Please, is there any t... | g63534 | [
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0.05980810150504112,
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0... |
<p>When making predictions with a random forest model, is it possible to associate the probability of a test case belonging to a class? For example, for a given test case, can we say that the probability of that test case belonging to the <code>setosa</code> class is 90%, <code>versicolor</code> class is 7% and <code>... | g21238 | [
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0.0... |
<p>Iterative proportional fitting is a way of adjusting 'internal cells' in a multidimensional matrix to optimise fit. It is also known as 'raking' and can be seen as a subset of 'entropy maximisation'.</p>
<p>The purpose for which I use IPF is to allocated individuals to zones. My code iteratively adjusts a weight fo... | g21239 | [
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-0.00191... |
<p>The standard exponential density is only defined for $x>0$ and scale parameter $\lambda > 0$ where the density is given by $f(x) = 1/ \lambda * exp(-x/ \lambda)$. </p>
<p>My question is, does a similar density where $\lambda < 0$ and $x < 0$ make any sense and have any interpretation? Similarly, what ab... | g63535 | [
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<p>I'm rusty on my stats. I am wondering what the prerequisites are for including covariates in my regression. I'm not looking for a prediction model but just the effect of the "treat". The sample was randomized and the demographics appear pretty similar with a couple of exceptions.</p>
<p>Do I include all or only tho... | g21241 | [
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0.04708327725529671,
0.031065920367836952,
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... |
<p>Suppose we are interested in an outcome variable $Y$. It can take four values $1,2,3,4$. These are categories. What would a probit link function do as opposed to a proportional odds model? Would a probit link model the outcome as $1 \ \text{versus} \ 2$, $2 \ \text{versus} \ 3$ and $3 \ \text{versus} \ 4$? Whereas t... | g21242 | [
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0.015358010306954384,
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<p>I have 3 covariates for 100 observations. How can I separate each of my 100 observations into groups as determined by the data. I was thinking clustering. However, apparently, I need more than 3 dimensions to do hierarchical clustering. Would some other clustering method work? How about PCA?</p>
<p>I've attached th... | g21244 | [
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<p>In the Arima package, using a Box-Cox transformation give wrong results when later applied to the forecast method.</p>
<p>For example, consider this data:</p>
<pre><code>library(forecast)
data<-c(2,3,2,3,2,3)
</code></pre>
<p>And for the sake of simplicity, consider an ARIMA(0,0,0) model. (The mean of this ser... | g63536 | [
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0.04251585528254509,
0.10156363993883133,
-0... |
<p>I am using a double model with log transformed independent variables and have calculated average partial effects. Now I am now not sure how to interpret the coefficients; particularly those from the first stage which is supposed to be capturing the probability of participation using a probit model. </p> | g63537 | [
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0.030131887644529343,
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0... |
<p>Let's say I have an experiment where I repeatedly measure something over Time (1:10), say 10 days. </p>
<p>Here I simulate some data...</p>
<pre><code>set.seed(101)
N = 10 # number of repeats
n = 10 # number of individuals
# Data
Time = rep(1:N,n) # measured over time
</code></pre>
<p>Note that I set the fixed ... | g21251 | [
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<p>Can some one give me some conceptual insight on the potential advantages of disadvantages of adding features that are (nonlinear) functions of existing features in training an SVM model with an RBF kernel? </p>
<p>For example, if I include area and perimeter as features then technically all of the information in s... | g63538 | [
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<p>If you have three quantile regression models with taus of 0.25, 0.5 and 0.75 and their coefficients how do you use these models to forecast a set of data not used to calculate the coefficients. In other words how do you do a cross validation quantile regression.</p> | g63539 | [
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0.033738162368535995,
-0.00... |
<p>So Here is the LDA Generative Model
<img src="http://i.stack.imgur.com/oW48y.png" alt="enter image description here"></p>
<p>The $\alpha$ and $\beta$ nodes represent the parameters for two Dirichlet distributions. The $\theta$ and $\phi$ nodes represent the parameters for two multinomial distributions. My questio... | g21254 | [
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0.043836526572704315,
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-0.0035371507983654737,
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0.026440592482686043,
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... |
<p>In my regression, I have a predictor (measured in proportions) with very low variance (.002). It had no significant effect on the outcome due to a very high standard error of the regression coefficient. </p>
<p>When reporting on the effect in a paper, is it right to say there was no effect of my predictor in my stu... | g10380 | [
0.03798612952232361,
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0.01942252740263939,
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0.05562867969274521,
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-0.06494124978780746,
0.011520447209477425,
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0.005503853317350149,
0.00... |
<p>I have used a random walk model and Gibbs sampling (more specifically RJAGS) in order to obtain posterior of the state given the observations. In this case the state is the true proportion of the population that will vote one way or the other.</p>
<p>I have used diagnostics to make sure that the Markov chains have ... | g63540 | [
-0.010538632981479168,
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-0.009517539292573929,
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0.02346882037818432,
0.030487388372421265,
-0.00... |
<p>The particle data group (PDG) has a particular rule to round the value of a measurement. You can find the complete description at this <a href="http://pdg.lbl.gov/2011/reviews/rpp2011-rev-rpp-intro.pdf" rel="nofollow">link</a> (page 13).</p>
<p>Summarizing:</p>
<blockquote>
<p>... if the three highest order digi... | g63541 | [
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-0.02055097557604313,
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0.07064637541770935,
0.04319131746888161,
-0.... |
<p>I was implementing a simple scheme of Bernoulli distribution sampler. $ X \sim B(p) $.
I have a function that generates a uniform random number $r \in (0,1)$. Then, I set $ X = 1 $ if $p > r $, and $X =0$ otherwise. Is this correct?</p> | g63542 | [
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-0.03411078080534935,
0.0359802171587944,
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... |
<p>I am using SAS to do clustering analysis on a huge dataset. Since my dataset contains various types of variables, I am confused about the appropriate method to perform the analysis. Here are my questions:</p>
<ol>
<li>How to deal with nominal variables?</li>
<li>I standardize the data to be analyzed using <code>PRO... | g63543 | [
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-0.0425841249525547,
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0.059202954173088074,
0.0219... |
<p>I conducted an experiment which measured a binary response for each subject. The subjects were in 1 of 3 groups. There were two other fixed factors, each of which were continuums (cont1, cont2) ranging from 0 to 10. In other words, for each step in cont1, there was a corresponding 0-10 step continuum (cont2). Cont1 ... | g63544 | [
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... |
<p>I am currently pursuing research in management, but I have a serious problem with selecting the right statistical method. </p>
<p>I have quarterly data for a couple of financial ratios (for example Return on Equity) for two groups of companies: those with CEOs with MBAs and those without MBAs. I want to test whethe... | g63545 | [
0.04087608680129051,
0.026389434933662415,
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-0.0005773382727056742,
0.09808235615491867,
-0.010902240872383118,
0.0007431177655234933,
0.0... |
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