question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I have three dependent random variables $X_1$, $X_2$, $X_3$, ($X_i\in\left[0, 1\right]$) that satisfy additional condition $\sum_i{X_i} = 1$.</p>
<p>If (marginal) distributions of $X_i$ ($i = 1, 2, 3$) are given, I need to determine likelihood of a certain combination of those variables. More formally, if $a_1, a_2... | 72,563 |
<p>Can SEM be conducted with a rank-based dependent variable? If so, which software package would be the way to go?</p>
<p>Obviously, you'll get LISREL output and such, but I'm concerned as to how the rank-based DV would affect parameter estimates and was wondering if something can be done to combat any bad things tha... | 34,549 |
<p>Suppose I want to model dependence between $d$ r.v.´s $Y_1,...,Y_d$ with the copula $C_\theta$, where $\theta$ are the corresponding parameters of that copula. I've also determined the correlation using Kendall's tau $\tau(Y_i,Y_j)=\gamma$ for all $i\neq j$. Now I want to generate samples from this joint distributio... | 34,550 |
<p>I asked on stackoverflow but they suggest me to move here for better answers. I copy paste the question.</p>
<p>I decide to play a little with similarities and clustering text.</p>
<p>I have already create the tf-idf and symmatrix matrix of similarities. Now I want to implement something for clustering into groups... | 72,564 |
<p>When I generate a random number using the following procedure:</p>
<pre><code>set.seed(123)
rnorm(1)
</code></pre>
<p>I would like to know what exactly is happening in this case?
Is R reading from a table of random numbers? What exactly is 123 referring to?
Is it possible to access this table to see how it looks... | 72,565 |
<p>I conducted a regression analysis using R's lm() function. One of the independent variables shows no significance (p = 0.89), which contradicts the hypothesis that is should have a significantly positive effect on the dependent variable. </p>
<p>How do you interpret that? Can you say that it has no positive effect ... | 34,552 |
<p>I am analyzing how users of specific service affect each other by observing communication between them and changes in membership plans. </p>
<p>The social network consists of 3M users and 40M connections among them. To determine the influence of a specific user I observe the sequence of membership plans changes. Fo... | 72,566 |
<p>I have a zero-inflated negative binomial model. I have used incidence rate ratios and I'm trying to interpret the coefficients in relation to my predictors. Most of my predictors are continuous variables of census data -- ie: % of the population that is Hispanic; % of the population less than age 18, etc. I know ... | 45,709 |
<p>I am looking for some references on weighted regression when we have only dummy variables for predictors. I would appreciate it. Thanks.</p> | 49,901 |
<p>I ran across a new paper from the Berkeley NLP group on statistical testing, <a href="http://www.cs.berkeley.edu/~tberg/papers/emnlp2012.pdf" rel="nofollow">An Empirical Investigation of Statistical Significance in NLP</a>. </p>
<p>There is pseudocode for computing a p-value in the paper, basically, the idea is tha... | 34,554 |
<p>Suppose we have $10$ boxes and we are interested in measuring the number of apples, oranges and pears in each. What is a good way to visualize how the boxes relate to each other in terms of the distribution of fruits? For example, box 1 might have 5 apples, 10 oranges, and 6 pears while box 10 might have 1 apple, 1 ... | 72,567 |
<p>I have a distribution of visitors to a website on Monday to Sunday like this: </p>
<pre><code>M T W Th F S Su
345 467 560 350 430 689 490
</code></pre>
<p>I know that if I have a hypothesis of distribution that I suspect such as (M 20%, T 30%, W 10%, Th 5%, F 5% S 20% Su 10%) etc, I can use a Chi Squa... | 72,568 |
<p>I am trying to estimate the surface (isochrone), $z_i(x)$ for which $T(x,z)=0$ from noisy measurements of $T(x,z)$ everywhere and 3 almost noise free control points:
<img src="http://i.stack.imgur.com/6eDJG.png" alt="isochrone"></p>
<p>Instead of using the $T(x,z)$ data directly I first estimate the gradient: $T_x$... | 72,569 |
<p>In 2012 we collected data at our university about retention of students from first semester to second semester along with some other variables. The retention variable is binary, 'retained' or 'did not retain'. </p>
<p>In 2013 we introduced a new system. Student success advisers were assigned and any student when ne... | 34,558 |
<p>Let $X$ be an integrable random variable defined on probability space $(\Omega , \mathcal F,P)$, and let $\mathcal F_{n},n\ge0$ , be a filtration on this space.<br>
show that $X_{n}= E[X|\mathcal F_{n}]$ is an $\mathcal F_{n}$-martingale.</p> | 34,559 |
<p>I just found out that machine learning also has logistic regression as one of its methods. Can someone please tell me the differences between logistic regression in statistics and machine learning? I've seen lecture slides on logistic regression from a machine learning course, but I can't see the difference with the... | 72,570 |
<p>I'm trying to use the <code>train</code> function from the caret package to tune the parameters of the <code>rxDForest</code> from RevoScaleR package (I can't use the random forest because my dataset is too big), but I can't manage to make my code work with resampling:</p>
<pre><code>library(caret)
library(doParall... | 18,713 |
<p>I am very new to statistic analysis and I am having some problems with my data. Basically, my categorical variables are the following: grammatical structures (four of them) and languages (five of them). The total number of these structures is 1218. </p>
<p>I want to answer the research question if the observed pref... | 72,571 |
<p>I am conducting research on the relationship between a person's birth order and later risk of obesity using data from several 1-year birth cohorts (e.g. <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908417/">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908417/</a>). </p>
<p>A key challenge is that birth ord... | 72,572 |
<p>I have a problem where I am trying to group observations (most likely using k-means or a similar unsupervised learning tool) where each observation includes <em>n</em>-variables, with the total sum of these variables equal to one. We are therefore grouping observations, based on the probabilities of each of <em>n</... | 34,563 |
<p>I am experimenting with a mixture of binomial models. Consider a binary variable $y_i$. Furthermore, there are two sub-groups in the population (not known a priori and not observable): $z_i=0$ or $z_i=1$.
For one sub-group of the population, the following holds true:
\begin{equation}
P(y_i=1|z_i=0)= \xi,
\end{equa... | 72,573 |
<p>Let $y_t$ a stochastic process and $\tau_t$ presents the time duration between the $t$ and $t-1$ event.The ARMA(p,q,r) with exogenous variables is defined as:</p>
<p>$$
y_t = \varepsilon_t + \sum_{i=1}^p \alpha_i y_{t-i} + \sum_{i=1}^q \theta_i \varepsilon_{t-i} + \sum_{i=0}^b \eta_i \tau_{t-i}.\,$$ </p>
<... | 6,572 |
<h2>Background</h2>
<p>I'm trying to understand the <em>first</em> example in a course on fitting
models (so this may seem ludicrously simple). I've done the calculations by hand and they match the example,
but when I repeat them in R, the model coefficients are off. I thought
the difference may be due to the textbook... | 72,574 |
<p>great site!</p>
<p>I have collected monthly deals data for how new ships are being finance from 2005-2012. The data consists of "deals" made by different shipping companies and the amount raised in each deal. The deals can split into the following categories: Bank Loans, Bonds, IPOs and FOs. </p>
<p>Bank loans ha... | 72,575 |
<p>I'm doing a multivariate linear regression with R, and i find myself with the following residuals vs fitted plot:</p>
<p><img src="http://i.stack.imgur.com/1azOo.png" alt="plot"></p>
<p>As you can see there is a very regular line of points that seems to follow a precise pattern.</p>
<p><strong>My questions are:</... | 34,567 |
<p>I am just wondering what we can infer from a graph with x-axis as the actual and y axis as the predicted data?</p>
<p><img src="http://i.stack.imgur.com/dwlOW.png" alt="signups"></p> | 34,568 |
<p>I am performing a significance test on the gain score between a Pre-Test (say Y1) and a Post-Test (say Y2) for a Treatment Group and a Control Group.</p>
<p>Let me give a brief background on the experiment. My client is working with a large group of schools on improving the learning levels of kids in Math. Out of t... | 34,569 |
<p>I have a set of cities ranked 1-10 based on several criteria. I also have the percentage of the total population living in these cities. I want the cities with smaller populations to be able to compete with larger cities, so I want to give the population percentages a weight that will compensate for smaller populati... | 72,576 |
<p>In preparation for my end of semester R exam, I've been working on the following CSV file which was modelled on R, which I'm currently having problems figuring out. The excercise is from the textbook'Applied Statistics: Principles and Examples' by D. David Roxbee Cox. </p>
<p><img src="http://i.stack.imgur.com/6wvq... | 72,577 |
<p>Suppose two sets of data $\mathbf{X}$ and $\mathbf{Y}$ have a correlation of $\rho_0$. Can anything be said about the correlation between $\mathbf{X}_1$ and $\mathbf{Y}_1$ and $\mathbf{X}_2$ and $\mathbf{Y}_2$ where $\mathbf{X}_1\cup \mathbf{X}_2=\mathbf{X}$ and $\mathbf{Y}_1\cup\mathbf{Y}_2 = \mathbf{Y}$ and $0<... | 72,578 |
<p>I am a CS undergraduate student and for my final project i developed a regression algorithm that is suited for large-scale datasets (i wouldn't say 'Big Data', but still large scale).</p>
<p>For the final results, i'm looking for regression algorithms that are known to successfully work on such large datasets, so i... | 777 |
<p>I've got a serious problem when trying to analyse the data of my psychological experiment. Here are the details of the experiment:</p>
<p>In each trial, subjects were presented with lateralized colored circles. They had to press a right button when the circle was red, or a left button when the circle was blue. The ... | 45,746 |
<p>I have came across a question in job interview aptitude test for critical thinking. It is goes something like this:</p>
<blockquote>
<p>The Zorganian Republic has some very strange customs. Couples only
wish to have female children as only females can inherit the family's
wealth, so if they have a male child ... | 231 |
<p>I am trying to write a prediction algorithm for a set of temperature data. I settled on Holt-Winters since it seemed to be a simple time series prediction algorithm and I can easily code it up in python to understand what is going on with it. </p>
<p>When I am plotting the smoothing function as it learns this is ho... | 72,579 |
<p>I have some items described by 43 categories like this:</p>
<pre><code>Dataset Item Category1 Category2... Category43
D1 Item1 1 0 0 ... 1 ...
D1 Item3 1 0 0 ... 1 ...
D2 Item4 1 0 0 ... 1 ...
..
</code></pre>... | 38,018 |
<p>How does Adaboost select best features from the sample data (or a unit feature vector)?</p>
<p>It would be nice if someone can explain if the above statement is true or not.</p>
<p>I've seen the term <em>features</em> and <em>classifiers</em> being used in place of each other in documentation that's available of A... | 34,575 |
<p>I am implementing random forest in my code, I find that when I build one tree, the oob error(mean square error since I do regression) is close to zero, while more tree is build, the oob error stablized, this is counter-intuitive, since the textbook teaches me that the oob error should decline as more trees builds, I... | 45,749 |
<p>I am building a model in R using support vector machine (SVM) with KBF kernel.
The model seems to work quite well. I would like to assess the relative importance of predictor variables.</p>
<p>Can anyone tell me how this can done. Does there exist an R script for that?</p> | 34,576 |
<p>I have a dataset consisting of two groups tested across three days. Therefore I run a linear mixed model as follows:
<code>model1 = lme(response ~ day*group, random=~1|ID, data)</code>, that reveals a significant interaction. </p>
<p>I would like to know if there is a difference between the groups in how they ... | 72,580 |
<p>I have a question:</p>
<blockquote>
<p>Does a sufficient statistic have to be one to one? For example, can $T(x) = x^2$ or $T(x) = |x|$ be sufficient statistics? I know that one to one functions of sufficient statistics are sufficient.</p>
</blockquote> | 72,581 |
<p>I am confused in the use of t-test. I monitored physical parameters of a river water two time (from the same site)- during winter and summer. Now I want to see the seasonal difference on physical properties, say for example water temperature. Should I use Independent Sample t-test; or paired sample t-test??</p> | 72,582 |
<p>At what point can very large samples, as a proportion of the population, be treated as a census? For example, if your sample contains 90% of the population units, can one dispense with inferential statistical inferences? What about 80%? And so on . . ..</p> | 72,583 |
<p>Using sample moments, how can the mean and variance estimators be improved if e.g. skewness and kurtosis are known exactly? And what about using estimates for these instead, which should imho be of no help?</p>
<p>In general then I would like to know if there are analogous approaches for other kinds of location and... | 72,584 |
<p>Say the minimum of k is 0 and the maximum of k is 4.</p>
<p>k is being derived from the <a href="http://en.wikipedia.org/wiki/Binomial_distribution#Example" rel="nofollow">probability mass function</a>, though I'm not using the formula because I do not have p of the distribution.</p>
<p>If I have
k(0) = 0.1852
k(... | 72,585 |
<p>Suppose that one investigates the two sources of variability with data $y_{ij}$ acquired from $j$th subject under $i$th session ($i=1,2; j=1,2..., n$). A linear mixed-effects model can be formulated as follows,</p>
<p>$$y_{ij} = \alpha_0 + b_i + c_j + \epsilon_{ij}$$</p>
<p>where $\alpha_0$ is a constant, $b_i$ an... | 72,586 |
<p>I am currently using the R package <a href="http://cran.r-project.org/web/packages/lme4/lme4.pdf">lme4</a>.</p>
<p>I am using a linear mixed effects models with random effects:</p>
<pre><code>library(lme4)
mod1 <- lmer(r1 ~ (1 | site), data = sample_set) #Only random effects
mod2 <- lmer(r1 ~ p1 + (1 | site)... | 72,587 |
<p>In multiple comparisons, suppose we have calculated $q$-values. Is it a $q$-value for each test, or a $q$-value for all the multiple comparisons?</p>
<p>Given a false discovery rate (FDR) threshold on FDR, are $q$-values used to determine whether to accept or reject each null? For an individual test, is it rejected... | 72,588 |
<p>Sometimes researchers (especially in collaborations) have two opposite but sound theories: There is a difference between two groups or there is only negligible difference. Now they ask their statistician. How should he approach the situation?</p>
<p>If he does a point hypothesis test, he favours the difference part... | 72,589 |
<p>I would have expected this to be covered in detail by the LIBSVM tutorial but after hours of wasting time googling for answers I've had to throw in the towel. What I am trying to do is rather trivial really. Right now I have a financial data set in CSV format:</p>
<pre><code>time,indicator1,indicator2,indicator3,ro... | 72,590 |
<p>I've been using GEEs in SPSS 22 to analyze my dissertation data and have discovered an interesting problem: when trying to figure out which subset of model factors have the lowest QICc, and therefore best fit my data, the QICc just keeps decreasing as I eliminate factors. Now, I know QICc penalizes for more factors ... | 72,591 |
<p>I Want to know how to use time and country dummies in fixed effects model?</p> | 49,902 |
<p>Lets say you give a set of users a set of polls, or give them a choice of foods to eat, or let them listen to a group of songs (guess like pandora). So looking at the choices that all the users make you can match user 1 with user 5 based on the the 1st 10 choices they make. </p>
<p>So you taking user 1 you presen... | 72,592 |
<p>I am studying the effect of social capital on households' income. I am doing multiple regression to estimate this effect. For this, I have households' income as dependent variable and social capital as explanatory variable. I have also included human capital and some other household characteristics as control variab... | 72,593 |
<p>I have conducted a research in which 120 people participated. For my survey I created two visual images (casual and clown). </p>
<ul>
<li>Sample 1 (n=60) conducted the interview with the casual person </li>
<li>Sample 2 (n=60) conducted the interview with the clown</li>
</ul>
<p>The first part of the survey (which... | 34,583 |
<p>I need to implement a backward stepwise regression. I read the chapter from "The Elements of Statistical Learning" however the explanation is poor here:</p>
<blockquote>
<p>Backward-stepwise selection starts with the full model, and
sequentially deletes the predictor that has the least impact on the
fit. The ... | 72,594 |
<p>I know that 95% of the observations under a normal distribution fall approximately under 2 standard deviations from the mean. Does this change when the distribution has fat tails? What is the name of the theorem that guarantees this?</p>
<p>Thanks beforehand.</p> | 72,595 |
<p>Today I was asked, whether a p-value of 0.05 (exactly) is considered significant (given alpha=5%) or not. I did not know the answer and Google turned up both answers: (a) the result is significant if p is less than 5% and (b) if p is less than 5% or equal to 5%.</p>
<p>Of course, none of these websites cited anyone... | 72,596 |
<p>Excuse my dumb question, but I did an univariate logistic regression where the sign of the coefficient of my variable was negative (and it was significant). Once I have input it into a multivariate regression, the sign of the coefficient of the same variable became positive (still significant). Why does this occur? ... | 34,584 |
<p>I had to repeat the analyses after dropping out one of the between-subject factors (order of the questionnaires) and the new means I got for other effects were different from those I had before. Can it be like that? Is that because the degrees of freedom changed?</p> | 72,597 |
<p>I'm working on a web app, and I'm creating some data viz tools for it. For one particular series, I've got an extremely wide variance in data values (0 to millions). We're using a column chart to view the data now, which of course results in some columns that are a pixel high or smaller. We already have some ways to... | 72,598 |
<p>I am not sure how this should be termed, so please correct me if you know a better term.</p>
<p>I've got two lists. One of 55 items (e.g: a vector of strings), the other of 92. The item names are similar but not identical.</p>
<p>I wish to find the best candidate*<em>s</em>* in the 92 list to the items in the 55... | 45,770 |
<p>I am running LOESS regression models in R, and I want to compare the outputs of 12 different models with varying sample sizes. I can describe the actual models in more details if it helps with answering the question. </p>
<p>Here are the sample sizes: </p>
<pre><code>Fastballs vs RHH 2008-09: 2002
Fastballs vs LHH... | 72,599 |
<p>I am analyzing a data set concerning intertidal communities. The data are percent cover (of seaweed, barnacles, mussels, etc) in quadrats. I am used to thinking about correspondence analysis (CA) in terms of species <em>counts,</em> and principle component analysis (PCA) as something more useful for linear environme... | 72,600 |
<p>I'm looking at changes in child obesity prevalence as well as other weight categories following an intervention. I'm trying to figure out which test to use for changes in a categorical dependent variable (I assigned values of 1-5 for children who were severely obese, obese, overweight, normal, underweight) pre and p... | 72,601 |
<p>Although I was trained as an engineer, I find that I'm becoming more interested in data mining. Right now I'm trying to investigate the field further. In particular, I would like to understand the different categories of software tools that exist and which tools are notable in each category and why. (Note that I d... | 72,602 |
<p>I have been reading a good book called <a href="http://gseacademic.harvard.edu/alda/" rel="nofollow">Applied Longitudinal Data Analysis: Modeling Change and Event Occurrence</a> by Judith Singer and John Willet. The book shows that by modeling in 2 levels, we can model the individual change in level 1 and in level 2... | 72,603 |
<p>How can I rewrite an AR(p) model in state-space form?
Max(p)=5 and I want to use Kalman Predictor.</p> | 72,604 |
<p>I am looking through articles citing an article I'm reading - and I wish to judge how much that citing article is "important" or "good" by itself.</p>
<p>one way of knowing would be if I had known how "distinguished" that journal was. Which leads me to my question:</p>
<p><strong>What measures are there (and wher... | 72,605 |
<p>In Logistic Regression, is there a need to be as concerned about multicollinearity as you would be in straight up OLS regression? </p>
<p>For example, with a logistic regression, where multicollinearity exists, would you need to be cautious (as you would in OLS regression) with taking inference from the Beta coeffi... | 72,606 |
<p>I'm trying to precompute the distributions of several random variables. In particular, these random variables are the results of functions evaluated at locations in a genome, so there will be on the order of 10^8 or 10^9 values for each. The functions are pretty smooth, so I don't think I'll lose much accuracy by on... | 45,780 |
<p>Wikipedia suggests that one way to look at <a href="http://en.wikipedia.org/wiki/Inter-rater_reliability#Intra-class_correlation_coefficient" rel="nofollow">inter-rater reliability</a> is to use a random effects model to compute <a href="http://en.wikipedia.org/wiki/Intra-class_correlation_coefficient#.22Modern.22_I... | 72,607 |
<p>I have run a survey with many respondents. There was a pool of questions, and each respondent was asked 3 of the questions (chosen uniformly at random and independently for each respondent).</p>
<p>Now I'm interested in comparing the fraction of respondents who answered question $i$ correctly to the fraction who a... | 20,425 |
<p>Where can I find resources to learn about change-point analysis ?</p>
<p>Hopefully, someone can advise me a <strong>textbook</strong> to read and it will cover both univariate change-point analysis and <em>multivariate</em> change-point analysis. </p>
<p>It will also be very helpful if someone can point me to some... | 72,608 |
<p>Say that you're making a political research, and you want to know how many people vote to Party A and how many vote to Party B. (There are only two choices.)</p>
<p>You make a random survey of 10 people, and find that 1 out of your 10 votes A, while the other 9 vote B.</p>
<p>What would you conclude is the average... | 72,609 |
<p>I'm working on improving a random forest model. I've done some clustering of the data using the <code>pvclust</code> package in R. I use ward and euclidean distances. My question is how do I go from the results of the clustering analysis to a better random forest. Do I need to run multiple <code>rf</code> object... | 39,633 |
<p>Perhaps my question is very simple, however I could not get a reliable solution for my problem. </p>
<p>Here is my problem:
Consider something as 'event' if this causes me a monetary loss equal to or above $x$ amount (say in USD). The number of such events (in a particular time interval, like say 10 years) follows ... | 34,597 |
<p>I asked this question on Stackoverflow:
<a href="http://stackoverflow.com/questions/8142118/incidence-rate-ratios-in-r-poisson-regression">http://stackoverflow.com/questions/8142118/incidence-rate-ratios-in-r-poisson-regression</a>
and was advised to post here instead.
I have data that looks like this</p>
<pre><co... | 34,598 |
<p>I would like to estimate the statistical significance of a Gaussian Mixture model that is calculated by <a href="http://cran.r-project.org/web/packages/mclust/index.html" rel="nofollow">Mclust</a>.</p>
<p>The output of Mclust includes both the optimal Bayesian information criterion (BIC) used to select the optimal ... | 34,599 |
<p>What would be an appropriate way to compare two logistic regression models with the same number of parameters (i.e., model 1 is not nested in model 2)? In my case, I cannot compare the models to a superset model with all predictors of both models, because including the differing parameters of both models results in ... | 34,600 |
<p>If I have a mean time to repair (MTTR) of 3 days and a mean time between failures (MTBF) of 9 days, and so an availability of MTBF/(MTTR + MTBF) = 9/12= 75%, can I expect that, on average, 75% of my machines will be available per day, lets say I have a large number machines? Do any assumptions need to be upheld in ... | 72,610 |
<p>I built a simple app that grabs events using eventbrite and meetup.com APIs and displays it based on your zip code. Now I'm trying to build a simple event recommender that will use events that you marked as interested/not-interested as a training set. Two main questions here:</p>
<ul>
<li>What would be the best way... | 34,602 |
<p>It is easy to produce a random variable with Dirichlet distribution using Gamma variables with the same scale parameter. If:</p>
<p>$ X_i \sim \text{Gamma}(\alpha_i, \beta) $ </p>
<p>Then:</p>
<p>$ \left(\frac{X_1}{\sum_j X_j},\; \ldots\; , \frac{X_n}{\sum_j X_j}\right) \sim \text{Dirichlet}(\alpha_1,\;\ldots\;,\... | 72,611 |
<p>What methods exist to test for the existence of any sort of dependence in a time series? This is in contrast to something like auto-correlation, which tests for a particular type of dependency. Is there something that can say if dependencies exist, in general, without necessarily determining what kind?</p>
<p>I h... | 72,612 |
<p>So I'm trying to determine a semi-efficient way to calculate the optimal (recurring) frequency of a set of data. The data only exists at random time periods, but it is assumed that the data set is complete.</p>
<p><strong>For example:</strong> Say that we had data recorded every time a movie was watched, for which ... | 72,613 |
<p>I am trying to find the local maxima for a probability density function (found using R's <code>density</code> method). I cannot do a simple "look around neighbors" method (where one looks around a point to see if it's a local maximum with respect to its neighbors) as there is a large volume of data. Furthermore, it ... | 72,614 |
<p>I've a distribution of numeric scores computed using real data ( my reference distribution ). After that I generated 100000 random distributions of numeric scores computed using points picked at random in a space of possible points.
So now I want to compare my reference distribtuion with these random distributions a... | 72,615 |
<p>I have pre - post data on quality of life, depression, and self-esteem. I hypothesize that changes in self-esteem from pre to post cause changes in depression, which in turn cause changes in quality of life, from pre to post. </p>
<p>This looks to me like two separate multiple regressions, but I am unsure whether ... | 34,604 |
<p>I have a proposed a model for Corporate Social Responsibility determinants (not important).
Among my independent variables I obtain two that are statistically not significant.
Following Wooldridge approach, in order to know if I should take out these two variables from the model, I should run a F-test, with the rest... | 72,616 |
<p>I have a dataset that I can collect some quantities from, eg. sum,mean,variance...
I want to perform a simple regression on column(x,y). According to Wikipedia, the closed form for $\alpha,\beta$ is</p>
<p>\begin{equation}
\alpha=\frac{Cov(x,y)}{Var(x)}
\quad \mbox{and} \quad
\beta=\bar{y}-\beta\bar{x}.
\end{equat... | 34,606 |
<p>I would like to check how two time series are correlated - how one of them predicts the other one. I have data for 27 years. I conduct my analysis in SPSS (Forecasting command, ARIMA) and I get:</p>
<p><img src="http://i.stack.imgur.com/lMJpN.png" alt="enter image description here"></p>
<p>Could somebody please te... | 34,607 |
<p>I have a variable whose values vary between $-\infty$ and $\infty$.<br>
I'd like to change its limits from $0$ to $1$. I want to give extremely low values when the values are less than $-1$ or greater than $1$ and want to give the highest value to the value $0$.</p>
<p>Which distribution would be the best here, and... | 72,617 |
<p>Normally the marginal probablity is computed as</p>
<p>$p(x) = \sum_y p(x | y) \cdot p(y) $</p>
<p>Now, suppose I have all these probabilities at the right-hand side in logspace (so as logprobabilities).</p>
<p>How do I do this?!?</p> | 72,618 |
<p>I would like to be able to predict when I will exhaust a particular resource.</p>
<p>My situation is analogous* to a water tank. Each day zero or more rain will fall, filling up the tank. I can not tell in advance how much rain will fall each day, if any at all. There will never be any outflow from the tank. Ea... | 72,619 |
<p>I'm trying to calculate the bias and variance of $\hat{\lambda}_{MLE}$ where $X \sim exponential(\lambda)$. </p>
<p>Secondly, does it attain the CRLB?</p>
<p>Attempt:
$$f_x(X) = \lambda e^{-\lambda x}$$
$$L(\lambda; x_1,...,x_n) = \lambda^n e^{-\lambda \sum^n X_i}$$
$$\ell(\lambda; x_1,...x_n) = n ln(x) - \lambda ... | 30,870 |
<p>The Goldman Sachs model was already discussed <a href="http://stats.stackexchange.com/questions/100715/can-goldman-sachs-economists-predict-who-will-win-the-world-cup">here</a>. I wonder whether there are other statistical forecasts publicly available, or even better, models including raw data. Specifically, I thoug... | 34,609 |
<p>I have a series of data points that consist of 1) a time, and 2) a win or a loss. I would like to be able to determine the aggregate win rate for particular time periods, and graph it.</p>
<p>For instance, let's say I am dealing with boxers. I would like to be able to say the boxer Bill tends to peak in boxing ma... | 72,620 |
<p>I've created a regression model on my data using random forests in R. The output is quite large, I'm wondering if there's any way to reduce this to only the necessary pieces to make a prediction?</p>
<p>The training data set contains 20 variables and ~45,000 rows, which is also large. My code is listed below.</p>
... | 72,621 |
<p>My colleague and I are fitting a range of linear and nonlinear mixed effect models in R. We are asked to perform cross-validation on the fitted models so that one can verify that the effects observed are relatively generalizable. This is normally a trivial task, but in our case, we have to split the whole data into ... | 49,822 |
<p>I have some data that I am really uncertain how to analyse. Each subject who all begin as healthy/normal will undergo a series of imaging examinations during therapy: scan 1 (baseline), scan 2, scan 3, ... scan N. These scans will then be processed and the gold standard parameter, say G, is measured. Now if G change... | 72,622 |
<p>Is a moment-generating function <a href="http://en.wikipedia.org/wiki/Moment-generating_function#Relation_to_other_functions" rel="nofollow">a Fourier transform of</a> a probability density function?</p>
<p>In other words, is a moment generating function just the spectral resolution of a probability density distrib... | 34,611 |
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