question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>There is an option for libSVM do an external validation (external data) like for cross validation (-v mode) ?</p>
<p>Thanks.
Andre</p> | 69,956 |
<p>I have developed a regression model, and found some issues with the overall process. As I do not have depth knowledge on regression, I need some expert advice. </p>
<p>I have n observations (4700+) from eight cases (C) for few years, and p candidate predictors (p=18). Assuming that the true model is a linear combin... | 69,957 |
<p>Am I looking for a better behaved distribution for the independent variable in question, or to reduce the effect of outliers, or something else?</p> | 49,325 |
<p>I know of Cameron and Trivedi's Microeconometrics Using Stata. </p>
<p>What are other good texts for learning Stata? </p> | 17 |
<p>We have a large number of (physical) legal files, and want to get an estimate of the average number of pages per file. I do not know what distribution of pages to expect, the number of pages will range from 1 to a large finite number.</p>
<p>My thought is to take a number of samples, count the number of pages in th... | 30,644 |
<p>Suppose that we have any social network (i.e. we know who is a friend of whom) and for some nodes in the network (i.e. the users), we also know their age (but not for everyone, as in a real network).</p>
<p>Now the question is, if we have no other information, what is the best way to estimate the age of any person ... | 69,958 |
<p>Lets say I have 10 different treatments and these 10 treatments can be considered combinations of 2 factors - as in a factorial design experiment. What do I miss if I treat this data as coming from a complete randomized design instead of a factorial design? What will be the consequences?</p> | 69,959 |
<p>In the comments of <a href="http://stats.stackexchange.com/questions/86887">this question</a>, it was pointed out that, when comparing two distributions, it is more natural and more general use the cumulative distribution (CDF) instead of the distribution (PDF).</p>
<p>The question is, why? I.e. what are the advant... | 69,960 |
<p>I'm a biologist with a very little statistical background and I've been encountering many questions during a recent dataset analysis.</p>
<p>I have two sets of values from measurement in different conditions plus one set of control measurement ('background').</p>
<p>I would like to remove the background from my 2 ... | 69,961 |
<p>In <a href="http://link.springer.com/article/10.1007/s11042-011-0938-3" rel="nofollow">this paper</a>, the author claimed there are three categories of spatial relations:</p>
<ul>
<li>Topological relations, which remain invariant under transformations
such as translation, scaling and rotating</li>
<li>Direction (or... | 30,646 |
<ol>
<li><p><a href="http://books.google.com/books?id=VHB4OSAmwcUC&lpg=PP1&pg=PA89#v=onepage&q&f=false" rel="nofollow">Brockwell and Davis's book</a> gives the autocovariance of a MA(q)
process. I wonder if the magnitude of its autocovariance
monotonically decreases before the lag $h$ increases over $q$... | 893 |
<p>I have some time series data, $X_t$, and I need to fit a heavy tail distribution to the first difference i.e. $Y_t=X_t-X_{t-1}$. Prior to fit this distribution, I need to test the iid (identical independent distribution) assumption. So far, I check the ACF (autocorrelation function) plot of $Y_t$ to see if there is ... | 69,962 |
<p>There are N players and M objects, each of the objects has a value. Each player has a strategy in choosing an object. Each round a player will choose an object, many players can choose the same object. However the value of each object is divided evenly among every player that has chosen it. There will be 9000 rounds... | 41,027 |
<p>I have data from a survey given to a patient group and control group. Both groups completed the same exact survey (Likert scale). One group has an n of only 5 or 6, the other n was about 15.</p>
<p>What test should I conduct to determine if there is a significant difference between the two groups answers on the sur... | 69,963 |
<p>I fitted my stress-strain data with cubic fits as shown in the figure below and added the corresponding straight lines (dashed and same color). The problem is I put these straight lines at my own discretion by means of visual inspection. So of course if someone else tries to add these tangent straight lines, that wo... | 30,650 |
<p>I want to develop a questionnaire. Because the target population are children, I used 3-point likert-type scale (0 1 2) for my items. Now I want to remove invariant items (i.e. the items not having enough variance). Are there any standards for determining minimum variance value according to different likert-type sca... | 69,964 |
<p>I’m estimating a single equation time series model with yearly data (70 observations). To eliminate or reduce the influence of autocorrelated residuals and to obtain unbiased standard errors, I want to try out the HAC (Newey-West) variance estimator. There are a lot of options with respect to choosing the “right” ke... | 69,965 |
<p>I have two paired samples. </p>
<p>$\text{Group 1}: X_1,X_2, ...,X_n$<br>
$\text{Group 2}: Y_1,\;Y_2,...,\;Y_n$. </p>
<p>$(X_1, Y_1)$, $(X_2, Y_2), ..., (X_n, Y_n)$ are paired respectively. </p>
<p>The null hypothesis is $\mu_{|X-Y|} = 0$,<br>
the alternative hypothesis is $\mu_{|X-Y|} > 0$ </p>
<p>What i... | 69,966 |
<p>I have repeat measures at 2 times points in a sample of people. There are 18k people at time 1, and 13k at time 2 (5000 lost to follow-up). </p>
<p>I want to regress an outcome Y measured at time 2 (and the outcome is not able to be measured at time 1) on set of predictors X measured at time 1. All variables have s... | 69,967 |
<pre><code>x <- c( 9, 5, 9, 10, 13, 8, 8, 13, 18, 30)
y <- c(10, 6, 9, 8, 11, 4, 1, 3, 3, 10)
wilcox.test(y, x, paired=TRUE, exact=FALSE, correct=FALSE)
</code></pre>
<p>How do you compute the $V$-statistic and statistical test in R's <code>wilcox.test()</code> by hand? I need the algorithm, but I cannot find... | 69,968 |
<p>This question is of a previous one that has not been answered yet (see the details of our experiment and question <a href="http://stats.stackexchange.com/questions/50374/how-to-deal-with-two-time-variables-in-panel-data-modelling-using-plm-package-in">here</a>). </p>
<p>We are now exploring a <strong>GEE</strong> (... | 30,655 |
<p>I am testing CAPM, Fama-French & Carhart-models (so a 1-factor, 3-factor and 4-factor model) for financial portfolios (60 observations). There is one type of portfolio with low R²'s.</p>
<ul>
<li>The CAPM model shows an Adj. R² of: 0,1457</li>
<li>The Fama-French model shows an Adj. R² of: 0,1260</li>
<li>The C... | 69,969 |
<p>I have read from multiple sources (<a href="http://epub.ub.uni-muenchen.de/2100/1/tr015.pdf" rel="nofollow">like this pdf</a>) that in a linear regression model, an ordinal variable can be obtained by imposing linear restrictions on its dummy coding.</p>
<p>e.g. $x$ is an ordinal variable ranging from <code>1 to 5<... | 69,970 |
<p>The basic question here is whether the following situation would warrant a repeated measures approach with a mixed effects model or not.</p>
<p>Let's say I have a set of grocery stores in 5 different geographic regions and I am evaluating the effects of 3 interventions on customer wait time for a cashier. The store... | 30,665 |
<p>Let's say you are trying to choose between two models. One has two significant fixed effects. The other includes only one of the two fixed effects from the aforementioned model but has a lower AIC (and the fixed effect is still significant). Which model should I choose?</p> | 69,971 |
<p>I have a set of players. They play against each other (pairwise). Pairs of players are chosen randomly. In any game, one player wins and another one loses. The players play with each other a limited number of games (some players play more games, some less). So, I have data (who wins against whom and how many times).... | 30,667 |
<p>I have two stationery time series that I want to see are they correlated or not. I decided to work with cross correlation, there is a good answer in <a href="http://stats.stackexchange.com/questions/29096/correlation-between-two-time-series">Correlation between two time series</a> but I dont know how to calculate p-... | 36,309 |
<p>I have a finite-state, time-independent Markov chain with two absorbing states which models educational outcomes (the absorbing states are completing and not completing). The transition probabilities are estimated by taking the proportions of people who move from one state to another at successive time points (based... | 41,066 |
<p>I would like to learn a bit more on interactive data visualization (zooming, pointing, brushing, point-mapping and so on). I would welcome any:</p>
<ol>
<li>Tutorial/guide/book(?)/video on <strong>how to use</strong> such methods for statistical exploration.</li>
<li>Pointers for good/interesting <strong>interacti... | 69,972 |
<p>I have hourly data for a variable for several years. I want to analyse each month separately. How do I arrange the data for the same month of different years?</p>
<p>For example, suppose I have Jan 1997, Jan 1998m and Jan 1999. Do I have to find a mean for say 18 Jan 1997, 18 Jan 1998 and 18 Jan1999. </p>
<p><stro... | 894 |
<p>I know this question might have been around before like in this SO <a href="http://stackoverflow.com/questions/2804001/panel-data-with-binary-dependent-variable-in-r">thread</a>, but maybe (hopefully) its answer has changed over time.</p>
<ul>
<li>Is there any package in R or an outline how to do panel regressions ... | 69,973 |
<p>How can the following tables be computed:</p>
<ul>
<li>Chi-Square table</li>
<li>Student t-table</li>
</ul>
<p>I'm looking for a formula or procedure used to make these tables.</p>
<h3>For example:</h3>
<p>If I have a given 'x'-value, as df(degree of freedom) with some confidence percentage 'y', I should be able... | 69,974 |
<p>I am writing my master´s thesis in finance on the topic of voluntary disclosure of financial targets in annual reports of manufacturing firms. </p>
<h3>Context</h3>
<ul>
<li>I have created a dependent variable that is an index of level of disclosure. </li>
<li>At the moment I am gathering firm characteristics as i... | 30,670 |
<p>I would like to use GLM and Elastic Net to select those relevant features + build a linear regression model (i.e., both prediction and understanding, so it would be better to be left with relatively few parameters). The output is continuous. It's $20000$ genes per $50$ cases. I've been reading about the <code>glmnet... | 69,975 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/10115/describe-how-a-domestic-fast-food-chain-with-plans-for-expanding-into-china-would">Describe how a domestic fast food chain with plans for expanding into China would be able to use a forecasting model.</a... | 69,976 |
<p>I have been doing multinomial logistic regression analysis using SPSS 19.
I have encountered the following problem when I run the analysis procedure:</p>
<blockquote>
<p>"Unexpected singularities in the
Hessian matrix are encountered. This
indicates that either some predictor
variables should be excluded or... | 69,977 |
<p>Is there a function in R that given a vector of numbers, returns another vector with the standard units corresponding to each value?</p>
<p>where...
standard unit: how many SDs a value is + or - from the mean</p>
<p>Example:</p>
<pre><code> x <- c(1,3,4,5,7) # note: mean=4, sd=2
su(x)
[1] -1.5 -0.5 0.... | 69,978 |
<p>Suppose we have two linear models:</p>
<p>\begin{align}
y &= \beta_0 + \beta_1 A + \beta_2 B + \epsilon & (1)\\
y &= \beta_0 + \beta_1 A + \epsilon & (2)
\end{align}</p>
<p>in which $A $ and $B$ are independent variables
uncorrelated to each other (i.e. zero collinearity).
I suspect that ... | 69,979 |
<p>My problem is that : I have the daily closed values of the initial index for DJUSER, MSCI, SP500, SPGSCI from 1 January 1999 to 31 December 2011. I want to transform them in to data of rolling annual returns.
How to do it using R? which package do I need to use?</p>
<p><img src="http://i.stack.imgur.com/frFJr.png" ... | 69,980 |
<p>I am using <code>LIBSVM</code> package (Matlab version) in order to perform wind power forecasting. My training dataset is quite big, approx. 52000 values of 4 parameters.</p>
<p>The code seems to run correctly but is quite slow and I get the following message:</p>
<pre><code>WARNING: using -h 0 may be faster
</co... | 69,981 |
<p>There is a large literature about the estimation of bayes factor using e.g. importance sampling (e.g. <a href="https://www.rocq.inria.fr/axis/COMPSTAT2010/TU-marin_paper.pdf" rel="nofollow">https://www.rocq.inria.fr/axis/COMPSTAT2010/TU-marin_paper.pdf</a>). Most (all?) of them investigate their properties on small ... | 30,672 |
<p>I've read that Minitab does not perform the Augmented Dickey-Fuller test; I can't find it myself. Is there an alternative function in the package that will run a unit-root test?</p> | 69,982 |
<p>This question is closely related to <a href="http://stats.stackexchange.com/questions/7969/how-to-quickly-sample-x-if-expx-gamma">this post</a></p>
<p>Suppose I have a random variable $X \sim \text{Gamma}(k, \theta)$, and I define $Y = \log(X)$. I would like to find the probability density function of $Y$.</p>
<p>... | 30,673 |
<p>I am constructing several degree day models using linear and non linear models. I need to compare my linear models to each other to see if they significantly differ. I also need to compare my non-linear models to see if they significantly differ. Further, I also need to see if my linear vs non-linear models differ.... | 49,112 |
<p>Say I have two conditional media for bacteria growth: a bacteriocidal drug and control. I want to see the effect of my bacteriocide on culture growth, so I set up 6 flasks: three with drug, three without. I take three independent measurements from each flask at each of many timepoints. I model the growth of my bacte... | 30,674 |
<p>Suppose that $(X_1, Y_1)$ and $(X_2, Y_2)$ are independent and have the same joint distribution $F_{X,Y}$, which is a known copula $C_{X,Y}(F(X), F(Y))$. Also, suppose that $V = X_1 + X_2$ and $W = Y_1 + Y_2$.</p>
<p>It would be great if someone could point me to a procedure for computing the copula $C_{V,W}(F(V), ... | 69,983 |
<p>I've been back-testing a trading system that balances a portfolio between the S&P (via SPY) and 20-year Treasury bonds (via TLT). Through data mining, I've been able to identify a trading strategy that produces a Sharpe ratio of 2.06 over a 6-year back-test.</p>
<p>I'm now trying to test my strategy against bo... | 69,984 |
<p>If $x_1, x_2, \ldots, x_n$ are i.i.d. negative binomial, then what is the distribution of $(x_1, x_2, \ldots, x_n)$ given</p>
<p>$x_1 + x_2 + \ldots + x_n = N\quad$?</p>
<p>$N$ is fixed. </p>
<p>If $x_1, x_2, \ldots, x_n$ are Poisson then, conditional on the total, $(x_1, x_2, \ldots, x_n)$ is multinomial. I am n... | 5,925 |
<p>I have a matrix of pairwise correlations between n items. Now I want to find a subset of k items with the least correlation. Thus there are two questions:</p>
<ol>
<li>Which is the appropriate measure for the correlation within that group?</li>
<li>How to find the group with the least correlation?</li>
</ol>
<p>Th... | 69,985 |
<p>On Twitter, I would like to assign weight to users based on how similar their bios are to a topic (e.g. technology would be a topic, the training set would be the bios of users who are known to be interested in technology). I was thinking of using LDA, where I would get the theta value (document-topic association) o... | 30,677 |
<p>I have a question about the generation of statistics from cross validation schemes for performance estimation (two classes classification in my case).</p>
<p>Before each experiment (K iterations) I randomly generate K folds from my pool of examples. Then I run the usual K-fold cross validation scheme to obtain perf... | 69,986 |
<p>Suppose we have $N$ users that can vote for a given question by "Yes" or "No". Each user have a probability which is considered as the confidence that we have in that user (e.g. a user may have a probability of 0.8 to answer the question correctly, and a probability of 0.2 to answer it wrongly). Each user requesst a... | 69,987 |
<p>As it is know local sensitivity analysis attempt to quantify the local impact of input factors on the model, through partial derivatives: a derivative of the outputs accordingly to the inputs, when the last ones are slightly perturbed. Many methods are used to estimates this derivatives: Direct method, Green Functio... | 69,988 |
<p>Suppose we fit a simple mixed / multilevel model with no predictors, which some call a <em>variance components model</em>:</p>
<p>$$ y_{ij} = \beta_0 + u_j + e_{ij} $$</p>
<p>where $u_j$ are the level-2 residuals and $e_{ij}$ are the level-1 residuals, and we obtain estimates, $\hat{\sigma_u^2}$ and $\hat{\sigma_e... | 30,678 |
<p>The book I read (Davidson,MacKinnon - <a href="http://rads.stackoverflow.com/amzn/click/0195123727" rel="nofollow">Econometric Theory and Methods</a>) describes the definition of "optimal instrument variables" as the following:</p>
<blockquote>
<p>Usually, and this is seen very often in other textbooks which cope... | 41,092 |
<p>I am trying to predict the probability that someone's vehicle fails its emission inspection a discrete number of times using a Poisson count model (actually a negative binomial hurdle model, but the same logic applies),
$$ P(y_i | X_i) = \dfrac{\exp(-e^{X\beta})(e^{X\beta})^{y_i} }{y_i!} $$
where the probability of... | 222 |
<p>When computing the Pearson correlation coefficient between a vector $X = \{x_1,...,x_n\}$ and a vector $Y = \{y_1,...,y_n\}$, we need to compute it as</p>
<p>$$\frac{1}{n}\sum_{i=1}^{i=n}(x_i-\bar{x})(y_i-\bar{y}).$$</p>
<p>Here $\bar{x} = (1/n)*\sum_{i=1}^{i=n}x_i$.</p>
<p>My question concerns the case where $x_... | 69,989 |
<p>The data consist of optical spectra (light intensity against frequency) recorded at varying times. The points were acquired on a regular grid in x (time) , y (frequency). In order to analyse the time evolution at specific frequencies (a fast rise, followed by an exponential decay), I would like to remove some of the... | 65 |
<p>We have two groups ($\mathbf{X}$ and $\mathbf{Y}$)
to test the equality of the means.
Suppose
$$
\mathbf{X}_i \sim MVN(\boldsymbol{\mu}_\mathbf{X},\boldsymbol{\Sigma}_\mathbf{X}),
\qquad
\mathbf{Y}_j \sim MVN(\boldsymbol{\mu}_\mathbf{Y},\boldsymbol{\Sigma}_\mathbf{Y})
$$
where $1 \leq i \leq n_\mathbf{X}$ and $1 \le... | 30,686 |
<p><strong>Question:</strong>
In one faculty the distribution of the heights of the students is N(180,25)
In the second faculty it's N(160,20)</p>
<p>We take some students from both faculties and put them together in a class.
There are 2 hypothesis regarding how they are distributed:</p>
<p>$H_0$: $\frac 14$ of them ... | 69,990 |
<p>I want to solve the
stochastic differential equation $$\mathrm dX(t)=X(t)^2 \mathrm dt+X(t)\mathrm dB(t)$$
with condition $X(0)=1$.</p> | 69,991 |
<p>Which is the most used classifier applied once PCA is performed?</p>
<p>I computed PCA on my data, and now I have the points projected on a line, I was wondering what is the preferred classifier. Is it a discriminant function for the normal density a good choice? Or is it better to use SVM? </p> | 69,992 |
<p>One estimate of the 'quality' of a portfolio of stocks is the <em>Sharpe ratio</em>, which is defined as the mean of the returns divided by the standard deviation of the returns (modulo adjustments for risk free rate, etc). The sample Sharpe ratio is the sample mean divided by the sample standard deviation. Up to a ... | 44,483 |
<p>I came across a <a href="http://www.citeulike.org/user/yaroslavvb/tag/information-geometry">large</a> body of literature which advocates using Fisher's Information metric as a natural local metric in the space of probability distributions and then integrating over it to define distances and volumes.</p>
<p>But are ... | 30,691 |
<p>Say I'm doing stats on the height of adults from various countries.</p>
<p>I assume the heights of adults from one country are normally distributed, and ignore sex differences (I also ignore the fact that neighbouring countries tend to have similar populations).</p>
<p>I have a bunch of data by country, but for so... | 30,692 |
<p>I am new to Gibbs Sampling, and have been using WinBUGS, but I find that it is not well-suited towards storing/presenting results, so I have been calling it from R using the R2WinBUGS package. The data is apparently stored as a "bug" class. </p>
<p>I converted it to coda to run diagnostics, and it displays each o... | 41,110 |
<p>In a recent paper, I fitted a three-way fixed effects models. Since one of the factors wasn't significant (p > 0.1), I removed it and refitted the model with two fixed effects and an interaction.</p>
<p>I've just had referees comments back, to quote:</p>
<blockquote>
<p>That time was not a significant factor
i... | 41,111 |
<p>How are the values in a z-table computed? Is it possible to compute confidence without looking up a z-table?</p> | 41,112 |
<p>I'm working with panel data. This panel dataset includes data from pupils of two kinds of schools: </p>
<ul>
<li><p>State schools (G1) where pupils change to secondary school when they are 12 years old.</p></li>
<li><p>Private schools (G2) where pupils remain in the same school. They can follow studying in the same... | 36,314 |
<p>With some great help from this forum, I have been able to get up and running with some basic time series analysis in R. Right now, my needs are mostly univariate time series. Here is my question:</p>
<p>I can read in daily data from database into a data frame. I have two columns, date which is understood by R as... | 69,993 |
<p>I am currently working on a linear classifier, which uses the statistical learning paradigm; that is, no knowledge about the distribution from which that training data are drawn from is available.</p>
<p>The resulting optimal solution is a hyperplane of the form $\mathcal{H}: \mathbf{w}\cdot\mathbf{x}+b$, where $\m... | 69,994 |
<p>Can someone explain what 'correlation among repeated measures' in G*power exactly means? I believe it is the test-retest reliability, but why is it important and what are the effects on the inferred sample size?</p> | 69,995 |
<p>My research is on "Effectiveness on Audit Committee Practices". I have collected the data using Five point Likert scale (1=Strongly Disagree to 5= Strongly Agree). Both Independent and Dependent variables are Five point Likert scale data type. Also each variable include 2 or 3 questions with Five point Likert scale.... | 49,595 |
<p>There are three boxes of gold coins. In the first box, 1 out of 3 coins are cursed, in the second 2 out of 3 are cursed, and in the third 1 out of 4 are cursed. Furthermore, the first box is ornate, and so has 3/5 chance of being picked, while the other two boxes have a 1/5 chance. The experiment consists of selecti... | 69,996 |
<p>I have a question regarding methodology in Machine Learning.</p>
<p>Assume we have a classification problem, the size of training set is 100 every instance in training set is represented by 200 features. In order to eliminate meaningless features we evaluate Information Gain / Mutual Information of every feature an... | 69,997 |
<p>This might sound like a trivial question, but I just can't get my head around it! </p>
<p>I am trying to evaluate the performance of different risk models (linear factor models), by computing the <strong><em>bias statistic</em></strong>. It is simply a function of estimated variance of the asset you are testing for... | 69,998 |
<p>The bivariate normal distribution with mean $\mu$ and covariance matrix $\Sigma$ can be <a href="http://www3.alcatel-lucent.com/bstj/vol26-1947/articles/bstj26-2-318.pdf">re-written in polar coordinates</a> with radius $r$ and angle $\theta$. My question is: <strong>What is the sampling distribution of $\hat{r}$, th... | 69,999 |
<p>What is a good way to visualize high dimensional (say n=10) <strong>binary</strong> data? I remember reading something about that a few years ago.</p>
<p>Say for instance, you want to plot / cluster pizzas based on their topping, e.g. ham, chicken, mushrooms etc.</p> | 41,124 |
<blockquote>
<p>Skulls were excavated from a dig. The sex of each skull was determined
by anatomical appreciation. For Sites A, the data was Male=162,
Female=110.</p>
<p>a) Find the exact p-value for a hypothesis test about whether the sex
ratio of the population buried at this sites was 1:1.</p>
<p>... | 70,000 |
<p>I have two groups of subjects (9 and 13 people). And data from two condition for this groups. In each condition for each subjects I have some measurements. But number of measurements are different for conditions (for second condition more then for first). First I use Wilcoxon-Mann-Whitney test for every subject to f... | 70,001 |
<p>I used a Monte-Carlo approach to estimate the prediction interval for a new observation from a GLM using a Negative Binomial distribution. I used this method for linear models and got reliable estimations of the prediction interval but I am not enough confident with statistics to know if this method could also be ap... | 49,839 |
<h3>Background:</h3>
<p>I have two groups of children - one group with normal hearing and one with permanent hearing losses - call them NH and PHL.</p>
<p>Each child has had a hearing test, consisting of 6 different sounds (.25, .5, 1, 2, 4, and 8KHz) assessed under three different test conditions (classic, remote, a... | 340 |
<p>I am studying individual differences in sound perception where I ask participants to listen to a pair of sounds and judge whether they are the same or different.</p>
<p>The answer choice and scoring are as below:
(number) is the score</p>
<pre><code>[Correct answer = Same]
Definitely Same (1) Probably Same (0.5) ... | 70,002 |
<p>I know some questions have been made for example between gentle and ada, but I was wondering about gentle and the others.</p>
<p>For instance, I saw two different works talking about AdaBoost.M1 and AdaBoost.M2 and another work only addressing Gentle, Real and the original Adaboost.</p>
<p>It seemed to me that the... | 44,557 |
<p>I recently analyzed an experiment that manipulated 2 categorical variables and one continuous variable using ANCOVA. However, a reviewer suggested that multiple regression with the categorical variable coded as dummy variables is a more appropriate test for experiments with both categorical and continuous variables... | 70,003 |
<p>I have not had much luck explaining my question so please do make a comment if you don't understand what I am asking.</p>
<p><strong>Core Question:</strong> How can I approach the problem of clustering text[not text document] based on the similarity of each word.</p>
<p><strong>Example :</strong> If I have a docum... | 41,133 |
<p>I have circular data such that multiple human participants were, each shown a color from a color wheel, asked to remember it for a "retention interval", then report it back by clicking a color wheel. Each participant was tested many times in each of two conditions testing conditions (short retention interval vs lon... | 30,708 |
<p>similar questions have been asked but have not managed to get a conclusion from them.
I am comparing two sets of samples, where ratios have been obtained for several analytes per sample. So the values are restricted to be in the [0,1] interval. One set of samples has been used as reference to set the limits for each... | 70,004 |
<p>I have two time-varying covariates (Residence Status [1 = In Residence, 0 = not in residence], and cumulative GPA. I would like to incorporate these variables into my Excel sheet before importing it into Stata and performing some survival analysis. However I am unsure about how to lay the data out.</p>
<p>I current... | 140 |
<p>I am running a factor analysis and have a couple of questions.</p>
<p>I have 10 variables, all of them come from a survey, with each answer is in the scale of 1 to 7. I have calculated a correlation matrix between the 10 variables, and looked for correlations of 0.5 or higher. These made me notice of 4 groups of co... | 30,711 |
<p>I want to analyse the effects of percentage mortality from two sources (a predator and a disease) on the population abundance of a host measured at 12 sites for 8 years, with the main aim being to look for any delayed density-dependent effects of the predator or disease on the host population. I plan to use GLMMs/GA... | 70,005 |
<p>I have read that $\chi_n^2 / n \to 1$ as $n \to \infty$. Is this true? If so how could I go about proving it?</p> | 70,006 |
<p>This question is a follow up for this one: <a href="https://stats.stackexchange.com/questions/27750/feature-selection-and-cross-validation">Feature selection and cross-validation</a></p>
<p>If I do cross-validation of a process that includes model (features) selection (so I re-do model selection for each fold), can... | 70,007 |
<p>In a regression, the interaction term wipes out both related direct effects. Do I drop the interaction or report the outcome? The interaction was not part of the original hypothesis. </p> | 49,395 |
<p>I am trying to figure out how to get odds based on a few factors and running into a few problems since I am a developer that is terrible at statistics/probability. My problem seems to be much like how the McDonalds Monopoly game functions with a few other variables.</p>
<p>Here is what I am working with:</p>
<ul>
... | 70,008 |
<p>All,</p>
<p>I am <em>trying</em> to study the GBM package in R. </p>
<p>I. I wanted to try and figure out where the deviance, initial value, gradient and terminal node estimates came from. Please see this snippet:</p>
<p><img src="http://i.stack.imgur.com/xeCwF.jpg" alt="alt text"></p>
<p>To start out, I was no... | 70,009 |
<p>Let's say you have a process that generates data according to r = sin(t) + epsilon, where epsilon ~ N(0,V) is Gaussian noise. The unconditional variance of r is 0.5 + V. </p>
<p>Let's say we're forecasting r with a model m, and that our forecast is "perfect" in that m = sin(t). Construct v = r - m, which is the for... | 33,636 |
<p>Many income surveys (especially older ones) truncate key variables, such as household income, at some arbitrary point, to protect confidentiality. This point changes over time. This reduces inequality measures associated with the variable. I am interested in fitting a Pareto tail to the truncated distribution, repla... | 70,010 |
<p>This question has been bugging me for some time, and I was going to write a blog post about it. However, I think it is better left for discussion in this forum. </p>
<p>Back in April, I attended a talk at the UMD Math Department Statistics group seminar series called "To Explain or To Predict?". The talk was given ... | 49,292 |
<p>When I tell my non-statistical friends I am a grad student pursuing a PhD in statistics they naturally say "oh so you want to be a professor?". I tell them no I actually plan to work in industry. Then they respond with, "and do what?". I have not found a good response to this question. I want to give them a rang... | 70,011 |
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