question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>Let $\mathbf{X}=(X_1,X_2,\ldots,X_{2k})$ be a sample from normal distribution $\mathcal{N}(0,1)$.</p>
<p>Prove that distribution of sample median (for even sample) is symmetric around 0.</p>
<p>$me(\mathbf{X}) = \frac{X_{k:2k}+X_{(k+1):2k}}{2}$, where $X_{i:2k}$ is $i$-th order statistic.</p>
<p>I was trying to u... | 74,468 |
<p>In a multiple regression analysis (with 4 continuous predictors and 2 categorical factors), we mean centered the data (for each continuous variable) due to issues of multicollinearity when the interaction terms are included. </p>
<p>My question is whether I can center the response variable too. </p>
<p>More specif... | 74,469 |
<p>I am studying disturbance caused by ship traffic to a small seabird. I observed focal animals for a set amount of time and record whether or not they fly from the water during the observation. This particular bird does not fly at high probabilities when not disturbed (about 10% of the time). Post hoc, I have appende... | 37,358 |
<p>How do you check ergodicity of a wide-sense stationary stochastic processes from its
sample path(s)? </p>
<p>Can we check ergodicity from a single sample path? Or do we need multiple sample paths? </p>
<p>One motivation of checking ergodicity is in time series to ensure that you could safely use the average of... | 74,470 |
<p>A new treatment for strokes is put on trial. There are two equal size groups,one group is given a drug, and one a placebo. The 95% confidence interval for the difference between the two proportion of subjects having strokes was (0.07,0.12). What can we infer:</p>
<p>1) not enough info to infer</p>
<p>2)at most 12%... | 74,471 |
<p>Is it possible to apply hurdle models (like the Craggit, probit and truncated models) to panel data, preferably with fixed effects to control for unobserved heterogeneity? </p>
<p>In Stata, the user-written command <code>craggit</code> only allows to use pooled panel data, but not to control for unobserved heteroge... | 37,360 |
<p>Asked a version of this question before but realized it needed some clarification.</p>
<p>I have a dataset with identical twin pairs and fraternal twin pairs. I want to examine the relationship between an outcome variable ("DEPENDENT") and a number of other variables ("INDEPENDENT"). However, I can't run a normal ... | 74,472 |
<p>Suppose that we have two data sets, <code>R</code> and <code>P</code>. <code>R</code> is larger than or equal to <code>P</code>. <code>R</code> can be negative or positive. <code>P</code> can be negative or positive. So in all cases <code>(R-P)</code> is positive or zero. the <code>R</code>and <code>P</code> are dol... | 7,030 |
<p>I am new to this area of machine learning. I am just walking myself through <code>UCB1</code> algorithm which seems to assume that the payoff can be learnt only for action that is taken. What I am curious about is if there is already analysis of the multi-armed bandit problem to the cases where the payoff can also b... | 74,473 |
<p>Given $n$ samples from a (continuous) distribution X, the obvious thing to do is sort them, and distribute them equally across $[0,1]$ by taking $(x_{(k)}, (k-1/2)/n)$ as estimates of particular points on the CDF, and doing some sort of interpolation between points, as necessary.</p>
<p>Is this the "right" way to ... | 74,474 |
<p>I'm doing a meta-analysis of some studies that report results variously as odds ratios, hazards ratios or rate ratios (all with confidence intervals). Is there any way to combine these together/convert between them so that I can do a meta-analysis of all the studies?</p> | 49,202 |
<h3>Overview:</h3>
<p>I want to test if "emotional numbing" is a significantly better predictor of "lower intimate relationship functioning" than "reexperiencing" or "hyperarousal"</p>
<p>It was suggested to me to use stepwise regression to analyze the data. However, one of my dissertation committee members suggested... | 293 |
<p>I am looking for a thesis topic for my Applied Economics degree where I can use Data Mining/Machine Learning for some kind of prediction.</p>
<p>Do you guys have any good ideas about what I could do?</p>
<p>My first thought was credit scoring, but that seems a little boring considering the number of papers out the... | 74,475 |
<p>Suppose that there is a Cricket match scheduled on Sunday, this weekend. We know that people do not arrive at the stadium at constant rate. Few hours before scheduled start of the match, people start arriving at very slow rate. This rate then, in general, keeps on increasing. A large number of people arrive just bef... | 37,366 |
<p>I fitted the Generalized Pareto distribution (GPD) using the <code>POT</code> package in <code>R</code>.</p>
<p>The fitted object provides shape and scale parameters, but not the location parameter. I need it to evaluate the quantile function with <code>qgpd(p, loc = 0, scale = 1, shape = 0, lower.tail = TRUE, lamb... | 74,476 |
<p>I have 4 latent variables each with 3-7 indicators. I created a composite for each variable by summing the data and then mean-centering (variables have some collinearity issues, highly related). Thus I have Var1, Var2, Var3, Var4.</p>
<p>I then wanted to create a master composite of all four variables. I thus su... | 74,477 |
<p>I have an experiment with two treatments. It is a split plot experiment, with the structure Block/Treatment1/Treatment2. Each treatment has 2 levels. The dependent variable is presence/absence data for functional speceis groups. I am analysing the data using mixed models via lme4 and afex.</p>
<p>The model st... | 74,478 |
<p>I'm trying to optimise model parameters for times series data using k-fold cross-validation. I'm using the forward chaining strategy described here:</p>
<p><a href="http://stats.stackexchange.com/questions/14099/using-k-fold-cross-validation-for-time-series-model-selection">Using k-fold cross-validation for time-se... | 74,479 |
<p>Let's say I'm computing some model parameters my minimizing the sum squared residuals, and I'm assuming my errors are Gaussian. My model produces analytical derivatives, so the optimizer does not need to use finite differences. Once the fit is complete, I want to calculate standard errors of the fitted parameters.</... | 74,480 |
<p>My study design involves a control and 2 test groups plus some covariates. Each group consists of around 20 observations. In total I look at around 1,000 variables.</p>
<p>I created a linear model using the <code>lm()</code> function in R including 2 covariates. After that I thought I would include another covariat... | 49,662 |
<p>I have a list of records with fields that can be seen as two sets of variables: dependent and independent. There are say 100 fields in each record and we consider 10 of them as dependent variables and 90 as independent. </p>
<p>What are the methods to find all the correlations that exist between the two sets?</p>
... | 49,217 |
<p>Please first have a look at the following little problem:</p>
<blockquote>
<p>There are two indistinguishable light bulbs A and B. A flashes red
light with prob .8 and blue with prob .2; B red with .2 and blue .8.
Now with .5 prob you are presented with either A or B. You're supposed
to observe its flash co... | 37,370 |
<p>I'm reading the results of an individual patient data (IPD) meta-analysis. The outcomes of the study is expressed in standard deviations (SD's). Comparisons between groups are stated as 0,23 (95% CI 0.15-0.33), SD 0.34, etc. I can't grasp how to interpretate this. Can somebody help?</p> | 74,481 |
<p>Documentation states that R gbm with distribution = "adaboost" can be used for 0-1 classification problem. Consider the following code fragment:</p>
<pre><code>gbm_algorithm <- gbm(y ~ ., data = train_dataset, distribution = "adaboost", n.trees = 5000)
gbm_predicted <- predict(gbm_algorithm, test_dataset, n.t... | 74,482 |
<p><em>I am not a statistician, so please excuse my lack of statistics knowledge/terminology.</em> </p>
<p>I have bunch of network nodes that I want to run cluster analysis on and identify clusters. So as far as I understand, I can follow the following steps to run a hierarchical agglomerative analysis (HAC):</p>
<ol... | 37,373 |
<p>I have a techincal issue with Stata: I need to calculate the SSE of a regression model, but the automatic output just gives me RMSE; I need SSE of this constrained model because I have to test if this model is better than the completely-free model.</p>
<p>SPSS gives me the SSE value in the regression output, but I ... | 40,405 |
<p>I have a large dataset from a survey that describes what web pages people use. So for each person I have a list of pages that they visit and how frequently they visit them. What methods can be used to cluster both the webpages (based on similar users who use them) and the users (who use similar webpages).</p>
<pre>... | 74,483 |
<p>I would be interested in finding ways in R for efficiently updating a linear model when an observation or a predictor is added. biglm has an updating capability when adding observations, but my data are small enough to reside in memory (although I do have a large number of instances to update). There are ways to do ... | 74,484 |
<p>Suppose I observe <em>i.i.d.</em> $x_i \sim \mathcal{N}\left(\mu,\Sigma\right)$, and wish to test $H_0: A\ $<a href="http://en.wikipedia.org/wiki/Vectorization_%28mathematics%29#Half-vectorization">vech</a>$\left(\Sigma^{-1}\right) = a$ for a conformable matrix $A$ and vector $a$. Is there known work on this problem... | 74,485 |
<p>I am confused how gaussian processes and kriging are related? Can anyone please give me some simple explanation. I tried to go through the wiki but I didn't get it</p> | 74,486 |
<p>I wanted to know what the <em>n.minobsinnode</em> parameter means in the GBM package. I read the manual, but it is not clear what it does.
Should that number be small or large to improve the results? </p> | 49,224 |
<p>I heard that the F-test is to advice you whether to use fixed effects or pooled OLS. However, I didn't find any details about it in books. Only in a very few studies. What is the hypothesis of the test? After I run my fixed model I got</p>
<pre><code>F test that all u_i=0: F(100, 389) = 2.98
Pro... | 7,034 |
<p>I am reviewing my time series knowledge and looking for a document that has the commonly-used time series tests, what they are used for, how to use them, etc. e.g. Augmented Dickey–Fuller test, PACF tests, etc. </p>
<p>I found a wikipedia page of common statistical tests, but I am looking for a list of such that is... | 74,487 |
<p>I was reading <a href="http://en.wikipedia.org/wiki/Gaussian_process_regression" rel="nofollow">this wikipedia article</a> related to kriging . I didn't understand the part when it says that</p>
<p>Kriging computes the best linear unbiased estimator, $\hat Z (x_0)$, of $Z(x_0)$ such that kriging variance of is min... | 74,488 |
<p>I have been looking for an alternative to Google Docs as a web based spreadsheet application as my employer's corporate firewall now blocks this application. I kicked around a few alternatives such as Zoho.com. I found the latter practically unusable. All its applications took a long time to load and really did n... | 74,489 |
<p>I am looking for methods which can be used to estimate the "OLS" measurement error model.</p>
<p>$$y_{i}=Y_{i}+e_{y,i}$$
$$x_{i}=X_{i}+e_{x,i}$$
$$Y_{i}=\alpha + \beta X_{i}$$</p>
<p>Where the errors are independent normal with unknown variances $\sigma_{y}^{2}$ and $\sigma_{x}^{2}$. "Standard" OLS won't work in ... | 37,379 |
<p>I'm looking at doing text classification/spam filtering using naive Bayesian classifiers with the e1071 or klaR package on R. Is there a good tutorial out there to describe this? I'm kind of stuck because I'm not sure what to use as the data to input into the NaiveBayes function.</p>
<p>Some help very much apprecia... | 74,490 |
<p>This is closely related to a question I asked yesterday but I've now got a much more complete answer on which I was hoping to get feedback. The previous question was just looking for conceptual advice and was very helpful. You can find the relevant data and introduction <a href="http://stats.stackexchange.com/questi... | 31,358 |
<p>I came in a new post because I’m quite confused with the use of an offset in gam() function (mgcv package). I’m actually working on predicting marine top predator’s distribution using aerial surveys (predators’ observations) and secondary production model outputs. My data are shaped in a 0.25° resolution grid, over ... | 41,855 |
<p>It is well known that most model selection algorithms can easily fall into a multiple comparison trap. To quote Friedman:</p>
<blockquote>
<p>Consider developing a regression model in a context where substantive
theory is weak. To focus on an extreme case, suppose that in fact
there is no relationship betwee... | 74,491 |
<p>So I have data like:</p>
<pre><code>Cost 20 30 10 5
Rating 5 3 2 5
</code></pre>
<p>I want to make a chart of rating vs. cost, so the points would be </p>
<pre><code>[(5,20), (3,30), (2,10), (5,5)]
</code></pre>
<p>I can't seem to get excel to do anything other than put the two rows as independent... | 74,492 |
<p>How to interpret the Null and Residual Deviance in GLM in R? Like we say the for AIC that smaller AIC is better, is there any similar and quick interpretation for the deviances also?</p>
<p>Null deviance: 1146.1 on 1077 degrees of freedom
Residual deviance: 4589.4 on 1099 degrees of freedom
AIC: 11089</p> | 37,385 |
<p>I am using the R 'multcomp' library (<a href="http://cran.r-project.org/web/packages/multcomp/" rel="nofollow">http://cran.r-project.org/web/packages/multcomp/</a>) to calculate Dunnett's test. I am using the script below:</p>
<pre><code>Group <- factor(c("A","A","B","B","B","C","C","C","D","D","D","E","E","F","... | 74,493 |
<p>i have a new data set which is basically as bad as the last (same sort of data) and have been asked to try non linear regression on it, with the focus on partition (I will be using boosting and bagging). The dependent variable is continuous however.</p>
<p>I require the input variables intact (as in not factorized)... | 37,388 |
<p>Say we have $N$ time series $X_t^i$ for $i=1...N$and we want to predict a separate time series $Y_t$. Let's consider the following model: $Y_t = \sum_{i} \beta_i X_{t-1}^i $</p>
<p>I am just trying to figure when such a model makes sense</p>
<ul>
<li>Does this model have a name? Is there an interpretation in terms... | 74,494 |
<p>Let's say I am using a logistic model to predict whether it rains (yes or no) based on the high temperature and have collected data for the past 100 days. Let's say that it rains 30/100 days. Furthermore, let's say that 70/100 days the temperature is actually 50 degrees. So there were only 30/100 days where the temp... | 37,390 |
<p>I am looking for a certain multivariate probability distribution function to fit to my data, but the usual multivariate normal distribution is unfit, since my data has a dent (antimode) instead of a peak in certain cases. (In other cases the data does have a peak.)</p>
<p>My data consists of data points with multip... | 74,495 |
<p>In my research I am working on some data (let’s call it sales data), however we almost have no information on the original sample. My goal is to come up with possible explanations on how it could be sampled by consistency arguments. </p>
<p>In more detail, the data provided is composed of sales transactions and it ... | 37,392 |
<p>I want to understand how the sampling distribution of the whole covariance matrix behaves for large $n$. I am trying to use the delta method and multivariate CLT. I am trying to show that when the $X$'s are IID with nonzero finite fourth order moments then the operation (sample variance) takes place, as in this equa... | 49,248 |
<p>After fitting a coxmodel it is possible to make predictions and retrieve the relative risk of new data. What I don't understand is how the relative risk is computed for an individual and what is it relative to (i.e. the average of the population)? Any recommendations for resources to help understand (I not very adv... | 74,496 |
<p>Should false discovery be controlled at the data acquisition level, or should this be at the data interpretation level?</p>
<p>I have an experiment in which microarrays were used to quantify the expression of about 30,000 genes (variables) in two groups of biological tissues (group-sizes of 75 and 76). Raw array da... | 49,249 |
<p>I am reading the article of wikipedia about <a href="http://en.wikipedia.org/wiki/Bayesian_average" rel="nofollow">bayesian average</a>. This seems very interesting about on developing rating systems, but I have a doubt. How to fix the weight C of the average?</p> | 74,497 |
<p>I am doing a regression analysis which troubled me. </p>
<p>My independent variable are 4 interplanetary condition components, and the dependent variable is the latitude of auroral oval boundary.
So far, the specific relationship is still unknown in physical principle, what we want to do is to get a model (functio... | 74,498 |
<p>This is a problem from the "7th Kolmogorov Student Olympiad in Probability Theory":</p>
<blockquote>
<p>Given one observation $X$ from a $\operatorname{Normal}(\mu,\sigma^2)$ distribution with both parameters unknown, give a confidence interval for $\sigma^2$ with a confidence level of at least 99%.</p>
</blockqu... | 37,394 |
<p>Stats noob here. I've been trying to find out if there is a technique to perform a certain type of analysis but so far a lot of searching hasn't yielded anything.</p>
<p>My question is, if a large peak or trough is identified in an organisation's overall rate, is there a way of identifying which of the organisation... | 74,499 |
<p>I want to know I often I need to crawl certain webpages, to make sure I have the newest content as fast as possible.
The naïve approach to this, is to simply calculate the average over a certain period of time. However, different web pages are updated at different rates, so this wouldn't be a good fit.
I did some go... | 74,500 |
<p>We have a small dataset (about 250 samples * 100 features) on which we want to build a binary classifier after selecting the best feature subset. Lets say that we partition the data into:</p>
<p>Training, Validation and Testing</p>
<p>For feature selection, we apply a wrapper model based on selecting features opti... | 49,252 |
<p>My understanding is that a hazard ratio from a Cox <a href="http://en.wikipedia.org/wiki/Proportional_hazards_model" rel="nofollow">proportional hazards model</a> compares the effect on the hazard rate of a given factor to a reference group. Does that actual group have to exist in the data?</p>
<p>Say we enroll pe... | 74,501 |
<p><em>Mathematics and Statistics are quite far behind in my educational curriculum, and yet now I seem to need them again, so this set of questions is very basic I suppose:</em></p>
<h2>What is a trend line? What various types of trend lines are there? And what are their respective use or relevance?</h2>
<h3>Backgro... | 37,397 |
<p>As science must be reproducible, by definition, there is increasing recognition that data and code are an essential component of the reproduciblity, as discussed by the <a href="http://reproducible-research.googlegroups.com/web/CISE-12-5-News.pdf">Yale Roundtable for data and code sharing</a>.</p>
<p>In reviewing a... | 74,502 |
<p>I am using SVM to predict diabetes. I am using the <a href="http://www.cdc.gov/BRFSS/">BRFSS</a> data set for this purpose. The data set has the dimensions of $432607 \times 136$ and is skewed. The percentage of <code>Y</code>s in the target variable is $11\%$ while the <code>N</code>s constitute the remaining $89\%... | 13,014 |
<p>I am working on a stock prediction model which predicts next day Open High Low and Close stock prices, my question is how to use RMSE and MAD to measure the error or accuracy for the entire model say 500 stocks? Or to clarify is the concept of RMSE and MAD useful only when looking at a single stock prediction error ... | 74,503 |
<p>I have about $50$ Bernoulli random variables $X_i$ whose joint distribution is unknown, but I can generate a sample of size on the order of $10^4$.
They are not independent, but I think the dependence is rather weak.
I would like to get some idea of ${\rm Pr}({\rm all}\ X_i = 1)$, which I expect to be
considerably... | 74,504 |
<p>I'm looking for insights on how to test the accuracy of a model I built to predict next days stock price - Open, High, Low and Close next day prices.</p>
<p>Is there a unique indicator of accuracy or standard approach that should be used to represent the accuracy of this system ? </p>
<p>This is a predictive model... | 74,505 |
<p>We have the following solar meteorology parameters through satellite data with resolution of 100 km$^2$ (10 km x 10 km). </p>
<p>Insolation on horizontal surface </p>
<p>Diffuse radiation on horizontal surface </p>
<p>Direct normal radiation </p>
<p>Like this we can have about 4-5 more paramet... | 74,506 |
<p>Let's say I have a grid of cells from a satellite image that take on the value of 0 or 1, with 1 being forest.</p>
<p>There are many spatial pattern metrics that measure things about this pattern such as some dimension of forest fragmentation.</p>
<p>A common one is the join-count statistic which is simple enough ... | 74,507 |
<p>I was just recently using the Student t-Test to check whether values from two samples could have an identical mean or not. I was wondering whether there is a complementary technique in bayesian statistics that does a similar thing.</p>
<p>Especially I am wondering about the $P$ values that I obtain as a result (<a ... | 74,508 |
<p>I am working on multi class imbalance data.I want to divide my classes based on one verus one method and then perform sampling techinque
How can I do that I just want to divide the classes not classification.
Is it possible in libsvm</p> | 22,166 |
<p>Suppose that the sample space S of some experiment is finite.
Show that the collection of all subsets of S satisfies the three conditions required to be called the collection of events:</p>
<ol>
<li>$S \in \beta $</li>
<li>$ if \; A \in \beta, \; A^\complement\in\beta$</li>
<li>$if A_{1},A_{2},\cdots,A_{n}\in\beta... | 43,009 |
<p>In many financial models we are interested in measuring the correlation between variables, returns etc. However, research shows that during crises times we observe "Correlation Breaks" where previously un-correlated variables become correlated.</p>
<p>What is the best way to quantify "stability of correlation" by e... | 37,407 |
<p>My data is as follows. I have two groups of patients. Patients in each group had a different type of eye surgery. 5 variables were measured on patients in each group. I want to compare those variables between the two groups using a permutation test or MANOVA. The eye on which the surgery was done does not really mat... | 37,408 |
<p>I am creating a small webapp and a part of it is generating a number (I like to call it diversity coefficient) that would represent how "diverse" someones listening habits are. The problem is - I am not sure how to create a valid formula for what I want. I will try my best to explain what information I have, and wha... | 74,509 |
<p>I'm trying to make sense of these two statements about UMP (uniformly most powerful) tests: </p>
<ol>
<li><p>If $g(t\mid\theta)~$ is a UMP then $~g(t\mid\theta_1)>k g(t\mid\theta_0)~\forall~t\in C$ and $g(t\mid\theta_1)<k g(t\mid\theta_0)~\forall~t\in C^c$</p></li>
<li><p>For $\mathbf X~i.i.d.~f(x\mid\the... | 74,510 |
<p>In the following example:</p>
<pre><code>x <- rnorm(100)
y <- rpois(100, exp(1+x))+10
g1 <- glm(y ~ x, family = Gamma(link = "log"))
par(mfrow = c(2,2))
plot(y~x)
plot(y,resid(g1))
plot(y,resid(g1$lm))
</code></pre>
<p>I am trying to look at the pattern in the predictor variable, i.e. if the model is 'co... | 74,511 |
<p>I came across a paper that uses the abbreviation "p.e.":</p>
<p><a href="http://www.jstor.org/stable/10.2307/2984884" rel="nofollow">Khatri and Madria, The Von Mises-Fisher Matrix Distribution in Orientation Statistics. 1976.</a></p>
<p>It's in Section 7 on page 105. I'm including a short excerpt:</p>
<blockquote... | 43,010 |
<p>Under the GARCH($m$,$s$) model, it can be shown that $ E(\eta_t\eta_{t-j}) = E[(a_t^{2}-\sigma_t^{2})(a_{t-j}^{2}-\sigma_{t-j}^{2})] = 0 $.</p>
<p>In my proof attempt, I came across $ E(\epsilon_t^{2}\epsilon_{t-j}^{2}) = 1 $ where $ \epsilon_t \sim^{iid} (0,1) $.</p>
<p>Is it indeed true that if $ \epsilon_t \sim... | 37,414 |
<blockquote>
<p>Let $X_{1},..,X_{n}$ be a sample from normal distribution with mean ${\theta}$ and variance 1. Let $H_{0}:{\theta}={\theta}_{0}$ and $H_{1}:{\theta}={\theta}_{1}$. Use the Neyman-Pearson lemma to show that the best test for $H_{0}$ vs $H_{1}$ has a critical region of the form mean$(X_{1},..,X_{n}){\ge... | 74,512 |
<p>I am trying to understand the relative behavior of the following rank correlation statistics:</p>
<ol>
<li>Spearman coefficient</li>
<li>Kendall Tau / Concordance percentage</li>
<li>Normalized Gini coefficient (area under curve of percentage captured versus percentage observations)</li>
<li>Normalized Area under R... | 74,513 |
<p>A rather elementary question: If we have:</p>
<p>$X = X_1 + X_2 + ... + X_n$ and $X_i \sim N(0,\sigma^2)$ and independent, </p>
<p>can we express $X$ as $\sqrt n X_i$ for any $i = 1,...,n$ ? </p>
<p>I think since all the components $X_i$ follow the normal distribution and we are summing $n$ of them up, the result... | 74,514 |
<p>What is the impact of data dimensionality on computation complexity of SVM? I found on the literature that the complexity of SVM is $O(N^3)$, where $N$ is the number of training examples. If the number of dimension (e.g., $D$) does not impact the training time why it s better to reduce the dimensionality for trainin... | 74,515 |
<p>I am running a pooled OLS regression and Random effects regression. </p>
<p>I have tested for autocorrelation for both methods. In the pooled OLS model I find serial correlation but for the RE model I find no serial correlation. </p>
<p>How is this possible? Is it possible that the unobserved time invariant variab... | 74,516 |
<p>In Frank Harrell's <a href="http://biostat.mc.vanderbilt.edu/wiki/Main/RmS" rel="nofollow">RMS Short Course</a> today, I became aware that multiple imputation with <code>Hmisc:aregImpute</code> is not invariant to the ordering of terms in its formula argument, and that one therefore ought to check results of imputat... | 37,417 |
<p>For an application I'm working on, I need to go from some uniformly distributed variables to an uniform distribution on an n-sphere. The standard way to do this seems to be choose (n+1) normal distributed variables, and then divide by the norm.</p>
<p>However, I need to be able to, given a point on the sphere, extr... | 74,517 |
<p>$X_{1}$ and $X_{2}$ are independent, chi-square distributed random variables. I've managed to show that $Z=X_{1}+X_{2}$ is independent of $\frac{X_{1}}{Z}$. How do I conclude then that $Z=X_{1}+X_{2}$ is independent of $(\frac{X_{1}}{Z},\frac{X_{2}}{Z})$? </p> | 37,421 |
<p>Regression: Wage=b0+b1collegegrad, where collegegrad is a dummy variable. Suppose you want to estimate the wage ratio between college graduates and non-college graduates. Is the estimator theta=b0/b1 consistent?</p>
<p>My thinking is that if we could increase our sample size to infinity, we would cover the entire p... | 74,518 |
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