question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I've written a program to simulate an <a href="http://cardshuffles.com/overhand-shuffle.htm" rel="nofollow">overhand</a> card shuffle. </p>
<p>Each card is numbered, with suit going from <code>CLUBS, DIAMONDS, HEARTS, SPADES</code> and the rank from Two up to Ten then Jack, Queen, King and Ace. Thus the Two of Cl... | 36,222 |
<p>My aim is to classify types of cars (Sedans,SUV,Hatchbacks) and earlier I was using corner features for classification but it didn't work out very well so now I am trying Gabor features.<br/></p>
<p><a href="http://www.mathworks.in/matlabcentral/fileexchange/38844-gabor-image-features" rel="nofollow">code from here... | 69,673 |
<p>The moment generating function of a random variable $X$ is defined to be the function $$M_{X}(t)=E(e^{tX})=\sum_{n=0}^{\infty}\frac{E(X^n)}{n!}t^n.$$ Let $I=\{t\in\mathbb R:M_{X}(t)<\infty\}.$</p>
<p>I wish to show that</p>
<ol>
<li><p>$I$ is possibly a degenerate interval and $0\in I$. (Degenerate means the in... | 49,553 |
<p>I have a matrix which looks like the attached image below, and I would like to know what's the statistically best educated guess for the missing steps (filled in orange) for the vector $\mathbf N$.</p>
<p>Please note that:</p>
<ul>
<li>The values are <em>binary</em>: they are always <code>0</code> or <code>1</code... | 438 |
<p>I created a matrix of dimensions 6X5 and applied the svd() function on it.</p>
<pre><code>>matrix_A
V W X Y Z
A 4 1 5 0 0
B 0 1 3 0 1
C 0 1 0 5 4
D 0 1 0 4 0
E 0 1 2 0 4
F 5 0 4 1 0
>svd_A <- svd(matrix_A)
</code></pre>
<p>When I see the 'U' matrix, it has dimensions 6X5.</p>
<pre><code>>svd_A$u
... | 69,674 |
<p>The following question is about an example from "The Elements of Statistical Learning" by Hastie, Friedman and Tibshirani</p>
<p>$X_1 = Z_1 $</p>
<p>$X_2 = X_1 + 0.001 * Z_2 $</p>
<p>$X_3 = 10 * Z_3 $</p>
<p>Where $ Z_1, Z_2 $ and $ Z_3 $ are independent standard normal variables.</p>
<p>According to Ex 14.15 ... | 30,259 |
<p>Disclaimer: I'm not a statistician but a software engineer. Most of my knowledge in statistics comes from self-education, thus I still have many gaps in understanding concepts that may seem trivial for other people here. So I would be very thankful if answers included less specific terms and more explanation. Imagin... | 69,675 |
<p>Is it feasible to use t-SNE to reduce a dataset to one dimension?</p>
<p>Suppose that I have a matrix, $X$, can I reduce it to a column vector, $Y$ with t-SNE?
Suppose that $X$ has 100 columns, how much information can I expect to lose by reducing it to just a column vector with t-SNE (if possible)?</p>
<p>Referen... | 69,676 |
<p>I am carrying a linear regression on some data. One of my variables is a factor (categorical). Using regression with an intercept leads to difficult interpretation, since one of the factor levels is taken as the intercept, and the remaining levels are given relative to that. Removing the intercept give me an effect ... | 41,190 |
<p>I am trying to sample from a Gamma distribution in JAGS</p>
<pre><code>gd[i] ~ dgamma(k,r)
</code></pre>
<p>where <strong>k</strong> and <strong>r</strong> are have priors such that they are positive. However I get the following error when I compile the model:</p>
<pre><code> Error in node gd[9]
Unobserved node ... | 30,262 |
<p>I think this is simple, and I am wrong-thinking it....</p>
<p>t-tests are used to test the null hypothesis that the means are equal;</p>
<p>$H_0 : \beta_1 = \beta_2$,
$H_1 : \beta_1 \neq \beta_2$</p>
<p>But I want to test the other way around;</p>
<p>$H_0 : \beta_1 \neq \beta_2$,
$H_1 : \beta_1 = \beta_2$</p>
... | 69,677 |
<p>I am having a hard time with what seems to be a very basic research design issue. </p>
<p>The study has 3 variables:</p>
<ul>
<li><code>Self-control</code> and <code>adjustment</code> are the main ones, since they were measured in pre and post tests, before and after a year long social and emotional program in two... | 69,678 |
<p>I'm doing a simulation study which requires bootstrapping estimates obtained from a generalized linear mixed model (actually, the product of two estimates for fixed effects, one from a GLMM and one from an LMM). To do the study well would require about 1000 simulations with 1000 or 1500 bootstrap replications each t... | 69,679 |
<p>I am trying to find a way to solve the following problem :</p>
<blockquote>
<p>I have some set <em>A</em>, which contains a set of <em>N</em> numbers, <em>X</em>, where <em>Xi</em> is a
number within <em>X</em>. The numbers in <em>X</em> are unique and they are in sorted
order.</p>
<p>I will draw <em>K<... | 69,680 |
<p>Our small team was having a discussion and got stuck. Does anyone know whether Cox regression has an underlying Poisson distribution. We had a debate that maybe Cox regression with constant time at risk will have similarities with Poisson regression with a robust variance. Any ideas?</p> | 69,681 |
<p>According to <a href="http://www.stat.psu.edu/online/courses/stat509/09_interim/09_interim_print.htm">this document</a>: <em>The estimated logarithm of the hazard ratio is approximately normally distributed with variance (1/d1) + (1/d2), where d1 and d2 are the numbers of events in the two treatment groups.</em></p>... | 69,682 |
<p>Suppose, I have a correlation coefficient of 0.6234 between Variables A and B, on a sample size of 20. My alpha threshold is 0.05. I want to do a power analysis on this result.</p>
<p>I found a calculator but it is asking for "Correlation p H1".</p>
<p>Does this refer to the correlation coefficient "r" (0.6234 as ... | 40,562 |
<p>I am not sure if this is an instance of vectorizing the operations in R, but this is where I am stuck:</p>
<p>I want to get: </p>
<pre><code>dpois(1, 0.1)
dpois(2, 0.2)
dpois(3, 0.3)
</code></pre>
<p>and I tried:</p>
<pre><code>dpois(1:3, 0.1:0.3)
</code></pre>
<p>and</p>
<pre><code>do.call(dpois, list(x = 1:3... | 69,683 |
<p>I have an idea for a lottery that is skewed in a fairly simple way:</p>
<p>The chance of winning is proportional to the square of each player's contribution, divided by the sum of the square of all players' contributions.</p>
<p>It might be expressed this way:</p>
<pre><code>Chance of winning = contribution^2 /
... | 69,684 |
<p>What inter-rate reliability test is best for continuous data? I am doing a study with one variable with continuous data, now the measurement involves measurements done by two people. I would wish to do inter-rater reliability test for the data, so far I have collected a few samples and a sample data I have given be... | 40,565 |
<p>I have a dependent variable which is ordinal, so based on logistic distribution. I need to run ordinal regression, but I have ratio scale independent variables as well as categorical: so how can I run this technique? Is it suitable? If yes, then, in which software?</p> | 69,685 |
<p>The Data:
The observed probability (proportions) of three mutually exclusive events for five species.</p>
<p>What is the best way to plot these data in R along with their standard errors? I'd like to avoid a "beside" bar plot with error bars (3 bars for each species). I was hoping to use a stacked bar plot, but I'm... | 69,686 |
<p>Is there any standard method to determine an "optimal" operation point on a <a href="http://en.wikipedia.org/wiki/Precision_and_recall" rel="nofollow">precision recall</a> curve? (i.e., determining the point on the curve that offers a good trade-off between precision and recall)</p>
<p>Thanks</p> | 69,687 |
<p>Supposing $\ X $ ~ $\chi_1^2 $ and $\ Y $ ~ $\chi_{10}^2$ and $\ X $ and $\ Y$ are independent. How would I calculate the probability that $\ X $ is bigger than $\ Y $?</p>
<p>I know that the ratio of $\ X/1$ and $\ Y/10$ would be $\ F$ distributed, but I don't know if that's helpful or not.</p>
<p>Can anyone help... | 69,688 |
<p>I need to predict the number of retweeets a tweet receives as a function of (1) whether there is a hyperlink within the tweet's text and (2) the position of the hyperlink within the tweet. If a tweet doesn't contain a hyperlink then the position of the hyperlink within the tweet is a null value. Example data for thi... | 5,865 |
<p>I collected data on the growth of juvenile fish from 4 different types of crosses using multiple distinct family blocks and I am trying to see if cross type has an effect on growth using linear mixed effects models. I have one fixed factor (Length), 3 categorical random factors (sire, dam and sire/dam interaction) a... | 11,889 |
<p>I would like to firstly smooth a periodogram with Daniell kernel, and then test if it is zero at some frequency of interest, following Shumway and Stoffer's book Time Series with R: </p>
<p><img src="http://i.stack.imgur.com/9042w.png" alt="enter image description here"></p>
<p>I wonder how to choose the window wi... | 69,689 |
<p>I am interested to learn about cognitive robotics and its application in situation assessment using natural language processing esp monitoring of human activities/disaster management.The processing would involve data visualization techniques. Can anyone suggest what is the starting point,which books to follow,the pr... | 69,690 |
<p>I am interested in understanding the graph plots we get after running <code>lm()</code> command (for linear regression) in R like, for example</p>
<pre><code>lm.mod1 = lm(y ~ x1 + x2)
</code></pre>
<p>I then get the do the summary by:</p>
<pre><code>summary(lm.mod1)
</code></pre>
<p>I get the result as: </p>
<p... | 30,277 |
<p>I have survey data that was recorded in a many different towns. I want to see for which variables is the data significantly more or less variable <em>within towns</em> than <em>across all towns</em>.</p>
<p>Currently, I'm thinking of conducting a Welch's t-test (for samples with unequal variance) on the difference ... | 30,278 |
<p>I have a question: how do I use rolling window forecasts in R:</p>
<p>I have 2 datasets: </p>
<ol>
<li>monthly data which I downloaded from Google. </li>
<li>monthly data I downloaded from the CBS (central bureau of statistics in Holland)</li>
</ol>
<p>I want to test whether I can build a valid forecasting model,... | 49,833 |
<p>As part of my master thesis, I'm performing several tests on panel data. One of these is a Fisher-type unit-root test, which works well with an unbalanced panel. I have performed the test, but I haven't managed to find an explanation of how to interpret the results.</p>
<p>This is the setup:</p>
<ul>
<li>Fisher-... | 49,932 |
<p>I'd like to build a predictive model for predicting churn for a website.</p>
<p>Here is the information I have for each customer :</p>
<p>What they did :</p>
<ul>
<li>visit the website </li>
<li>Buy something</li>
<li>Do not read thenewsletter</li>
<li>Read thenewsletter</li>
</ul>
<p>and when :</p>
<ul>
<li>th... | 30,282 |
<p>I have collected speech perception performance in children during one-year followed-up (four time points). A battery of speech perception measures (i.e., five measures) were used at each test interval. I want to examine the effects of three variables on speech perception performance (i.e., gender, chronological age,... | 30,284 |
<p>I am trying to run a Christiano FitzGerald band pass filter to estimate a long-run trend (with period in excess of 70 years). My data are the demeaned natural log of a commodity price index. My problem is that the asymmetric CF filter output does not look right around the start and end points. In particular my long ... | 30,286 |
<p>I am trying to find the association of BMI on the age at onset of hypertension in diabetes vs non-diabetes patients. Or in other words,
does diabetes (if the patient is already diabetic before the hypertension diagnosis) modify the association of BMI and age at onset of hypertension.</p>
<p>To find this, I have t... | 69,691 |
<p>I hope this is not a stupid question to ask. Let's say I have 5 years' data of 10 banks for 7 ratios; 1 ratio is dependent the other 6 is independent.
If I ignore the time and bank effects in this cross-sectional data it is called "pooled data."</p>
<p>Is this pooled data different from the not-pooled data in term... | 69,692 |
<p>Is it possible to compare variable importance, obtained for different models, built on different datasets with simular variables, using caret package? The property are different, but close, and the variables used for modelling are the same. For example, one can calculate importance for pls and random forest model, t... | 69,693 |
<p>In R, Lets say that I have a set of x and y points, how can I get a <code>geom_polygon</code> to encapsulate all points, ie, what is the best way to create a 'bounding' polygon for the set?</p>
<pre><code>library(ggplot2)
set.seed(1)
x <- runif(100)
y <- runif(100)
mydata <- data.frame(x,y)
ggplot(mydata... | 49,834 |
<p>Consider a $M/E_2/1$ queueing system, where the customer arrival rate is $\lambda$ and the service time distribution has a gamma distribution with parameters $2$ and $\mu$, i.e. with p.d.f. $\mu^2te^{-\mu t}$ , $t ≥ 0$</p>
<p>(1) How can I determine the mean of the service time distribution?</p>
<p>(2) What is the... | 134 |
<p>Often in research articles you read the researchers have controlled for certain variables. This can be done by methods such as matching, blocking, etc.</p>
<p>But I always thought controlling for variables was something done statistically by measuring several variables that could be of influence and performing some... | 40,600 |
<p>I was wondering if there is an online algorithm like Welford 1962 algorithm exists for computing the variance of complex numbers.
Check these links for more information:</p>
<p><a href="http://www.johndcook.com/standard_deviation.html" rel="nofollow">Accurately computing running variance</a></p>
<p><a href="http:/... | 40,603 |
<p>What is a reference that describes the "generalized likelihood ratio" test to determine <strong>online</strong> (i.e., meaning that we add an observation, then check, then add an observation, then check) whether the mean of a time-series has shifted?</p>
<p>I need descriptions of algorithms to be implemented into ... | 41,507 |
<p>I was referring to this wikipedia article for calculating the variance of a variable X which is the linear combination of other variables. As given there</p>
<p>$$
Var(\sum_{i=1}^{i=N}a_iX_i) = \sum_{i=1}^{i=N}a_iVar(X_i) + 2\sum_{i<j}a_ia_jCov(X_i,X_j)
$$</p>
<p>Now suppose I have different parameters suppose ... | 44,684 |
<p>Most measurements have measurement errors.</p>
<ol>
<li>Should measurement errors and uncertainty be accounted for in every statistical test?</li>
<li>Are duplicates better than single measurements if the sample size is large enough?</li>
</ol> | 30,291 |
<p>I am analyzing a data set using a one-way, within-subjects anova with 12 levels. Each of the levels represents a unique trial type in a reaction time experiment. However, the trials can be reasonably grouped together into 4 equal groups, let us call them A through D. My primary interest is in showing that A differs ... | 69,694 |
<p>Heyo-</p>
<p>I just started fooling around with R and want to find a good tutorial. Suggestions? </p>
<p>Also, are there other things I should be doing to beef up my R chops? </p>
<p>Context: very little coding experience, intermediate knowledge of SPSS</p>
<p>Much obliged.</p> | 49,454 |
<p>I have a feed forward neural network (1 hidden layer with 10 neurons, 1 output layer with 1 neuron) with no activation function (only transfer by weight + bias) that can learn a really wonky sin wave (using a 2in1out window) with production usable accuracy trained via stochastic climbing in a couple seconds:</p>
<p... | 69,695 |
<p>Task : Unfair die(6 sides) is being rolled n times. Probability of 1 is p1, probability of 2 is p2 and so on. Write a computer program, that for given n (n<100), the probability of set (p1,p2,p3,p4,p5,p6) and $x \in [n,600n]$ would find the probability of sum of dice values is less than x. Program cannot work mor... | 69,696 |
<p>I have to cluster a movie dataset of 10000 movies. A movie has attributes like Genres, Actors, Directors, Year. Earlier I thought that we can use a simple clustering algorithm like k-medoids and the distance can be pre-computed between two movies by subtracting genres & actors.</p>
<pre><code>Initialise d(movie... | 30,295 |
<p>In the last months I have read intensively about quantile regression in preparation for my master thesis this summer. Specifically I have read most of Roger Koenker's 2005 book on the topic. Now I want to expand this existing knowledge to quantile regression techniques that allow for instrumental variables (IV). Thi... | 69,697 |
<p>If we have a generative model: $X_2=X_1a_1+\varepsilon$, where $\varepsilon \sim \mathcal{N}(0,\sigma_2^2)$, do we have $X_1=X_2a_2+\varepsilon '$, where $\varepsilon \sim \mathcal{N}(0,\sigma_1^2)$ meaning unidentifiability?</p>
<p>The context is the search of a structure (more complex than 1-1) between correlate... | 69,698 |
<p>I have a formal model from which I'm deriving some parameters that I would like to estimate. I haven't done this kind of thing before, and I'd like to have some help to solve this issue in R. I observe $z_i$ (money) and four characteristics of population. I want to regress these characteristics on $z_i$. My regressi... | 40,618 |
<p>My question relates to recent work on correlated random effects probit models (see these <a href="https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCwQFjAA&url=http%3A%2F%2Fecon.msu.edu%2Ffaculty%2Fwooldridge%2Fdocs%2Fcre1_r4.pdf&ei=2EtRU-yNH... | 69,699 |
<p>Assume that I have a log transformed model as follows:</p>
<p>Model 1: Y = a + b*ln(x) -> Interpretation: A 1% increase in X is associated with an average b/100 units increase in Y.</p>
<p>If I add 1 to X to avoid having 0 values and get:</p>
<p>Model 2: Y = c + d*ln(x+1)</p>
<p>Should I interpret the model as "... | 30,300 |
<p>i'm not sure what statistical test to use to compare a scenario like this:</p>
<p>I have a list of candidate regions A (560k regions) and I want to know if my candidate regions enrich for a particular set of attributes X (14k items). So I did an overlap with A and X and the overlap is 3300 of X overlapping A. </p>
... | 69,700 |
<p>I am doing some self study on statistics and noticed that in the notes that I was using the $|Z|$ expression as attached in the photos below. I am confused with the "$|$" that is being used. The only logical conclusion that I was able to draw was that $P(|Z|\le 2)$ represents $P(-2 < Z < 2)$. </p>
<p>I would ... | 69,701 |
<p>Suppose that $X_1$ and $X_2$ are two random variables sampled from a Poisson distribution with parameter $\mu$. Let $T_1=\bar{X}$ be the sample mean and let $T_2=(1/3)X_1 +(2/3)X_2$.</p>
<p>Are T1 and T2 both unbiased estimators?</p> | 69,702 |
<p>I was reading Andrew Ng's <a href="http://cs229.stanford.edu/notes/cs229-notes12.pdf" rel="nofollow">lecture notes</a> on Reinforcement learning and was trying to understand why policy iteration converged to the optimal value function $V^*$ and optimum policy $\pi^*$. </p>
<p>Recall policy iteration is:</p>
<p>$
\... | 69,703 |
<p>I am trying to evaluate how well (or bad) a semi-supervised algorithm is performing on a given dataset. The algorithms assigns one of 10 labels to each data point. The dataset is huge, and it's not possible to obtain gold standard labels to each data point. Up until now, I have only come across papers where the eval... | 30,304 |
<p>I meet this real life problem. The simplified version is this:</p>
<p>Assuming I have 10000 apples, either good or bad. What is the sample size if I want to be 95% sure that all the apples are good?</p> | 69,704 |
<p>I cannot understand how step 2 transformed to step 3,
anybody help me please ??? </p>
<p><img src="http://i.stack.imgur.com/bsghu.png" alt="enter image description here"></p> | 112 |
<p>I have data collected on five species of fish at half a dozen locations in a lake over four years. The categories are not (at all) fully crossed, and I have a lot of empty cells due to logistical challenges with the sampling. I'm interested in comparing the effect of location and year on the variance. Despite the... | 69,705 |
<p>There are three breeds of total 80 animals, timed with 200 repeated observations/animal; response variable is milk yield (MY), predictor is day from birth (DFC) . I performed a mixed model on this data set, considering animal as random effect, also I included the interaction term between DFC and breed to see if the... | 69,706 |
<p>If the Kullback-Leibler distance between f and g is zero then f = g almost surely. I am really having trouble solving this. It should be simple!</p> | 69,707 |
<p>Which statistical test can I use to test if DNA damage is different between 4 cell types with respect to each other (comparing 2 cell lines at one time). The data does not seem to be normally distributed, and I have 3 experiments for each condition.</p> | 69,708 |
<p>I have 21 items that should load onto four factors. Several of these items had been reverse-coded. However, in a factor analysis, all the reverse coded items load onto one factor (when they actually should load onto four separate ones). I had reverse coded those items prior to running the CFA, but a previous questi... | 69,709 |
<p>Why and when we should use Mutual Information over statistical correlation measurements such as "Pearson", "spearman", or "Kendall's tau" ?</p> | 69,710 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/3115/cross-correlation-significance-in-r">Cross-correlation significance in R</a> </p>
</blockquote>
<p>How can I test the significance of the correlation coefficient? I have two time series and I want to ... | 49,323 |
<p>I've used a wide array of tests for my thesis data, from parametric ANOVAs and t-tests to non-parametric Kruskal-Wallis tests and Mann-Whitneys, as well as rank-transformed 2-way ANOVAs, and GzLMs with binary, poisson and proportional data. Now I need to report everything as I write all of this up in my results.</p>... | 30,313 |
<p><strong>In plain English:</strong>
I have a multiple regression or ANOVA model but the response variable for each individual is a curvilinear function of time. </p>
<ul>
<li>How can I tell which of the right-hand-side variables are responsible for significant differences in the shapes or vertical offsets of the c... | 69,711 |
<p>I know, this may sound like it is off-topic, but hear me out. </p>
<p>At Stack Overflow and here we get votes on posts, this is all stored in a tabular form.</p>
<p>E.g.:</p>
<pre>
post id voter id vote type datetime
------- -------- --------- --------
10 1 2 2... | 69,712 |
<p>I am working through a problem on CI for a sample mean and I cannot get the answer listed in the text I have. I am wondering if I am missing something or whether the text may be incorrect.</p>
<p>We are given a sample of 10 scores: </p>
<pre><code>45,38,52,48,25,39,51,46,55,46
</code></pre>
<p>I get a mean of 44... | 69,713 |
<p>this question started as "<a href="http://stats.stackexchange.com/questions/9739/clustering-spatial-data-in-r">Clustering spatial data in R</a>" and now has moved to DBSCAN question.</p>
<p>As the responses to the first question suggested I searched information about DBSCAN and read some docs about. New questions h... | 69,714 |
<p>is anybody familiar with the <code>tobit()</code> command using the package AER? I'm searching for a command to compute the marginal effects for y (not for the latent variable y*). It seems to be $\phi(x\beta/\sigma)\beta$, where $\phi$ is the std.normal cumulative distribution function. But how can I compute those ... | 30,317 |
<p>In my experiment, I have 312 separate samples, each of which is made up of several different food items. I multiply each food by a specific multiplier to convert it to energy, and then sum the energy in each sample to get a total energy value for the sample. There are several different multipliers possible to select... | 69,715 |
<p>I have some microarray data (~15 samples) which I've clustered via pam, with a range of cluster sizes and I want to find out the optimal k with BIC.</p>
<p>I basically want to re-implement the BIC score from the x-means paper and <a href="http://stats.stackexchange.com/questions/13103/x-mean-algorithm-bic-calculati... | 31,168 |
<p>My dependent variable are reaction times (RTs) in a psychological experiment. The experiment features a control condition and an experimental condition and for each subject, I have several hundred realizations of each condition (the variance in this experiment is pretty large, both the intra- and inter-individual). ... | 69,716 |
<p>I was wondering whether you have a suggestion on how to program a specific R-program for (a lot of) d20 testing.</p>
<p>I have the null hypothesis that the face-up value of any dice (I'm mostly interested in d20, but the mechanic is the same) does not have any effect, positive or negative bias, on the coming roll. ... | 40,634 |
<p>My website has advertising for various companies - say 10,000 companies. Each company has it's own page but all the pages are currently similar except by which company is on the page. A success/response/dependent variable is a visitor clicking on the advertisement. Each company's page has a different success rate... | 69,717 |
<p>There is an NPR podcast called Intelligence Squared. Each episode is a broadcasting of a live debate on some contentious statement such as "The 2nd amendment is no longer relevant" or "Affirmative action on college campuses does more harm than good". Four representatives debate-- two for the motion and two against.<... | 69,718 |
<p>Suppose I have an MLE estimate $\hat{\theta}$ for a parameter $\theta$, and $\hat{\sigma}$ is the sqrt of the inverse of the negative of the Hessian of the log likelihood at $\hat{\theta}$. Can I write $\hat{\theta} \pm \hat{\sigma}$?</p>
<p>In general, if I have an estimate $\hat{\theta}$ for a parameter $\theta$,... | 69,719 |
<p>In the <a href="http://www.gaussianprocess.org/gpml/code/matlab/doc/" rel="nofollow">documentation for GPML</a>, the author trained a GP with an affine mean function and isotropic squared exponential covariance function. Then there is an exercise to the reader:</p>
<blockquote>
<p>Try training a GP where the affi... | 30,324 |
<p>I have a set of count data that seems to fit "Poisson" = not overdispersed, alpha = 0.</p>
<p>The problem is, I get different results using <code>gamlss</code> vs <code>glmer</code>. Any help explaining the difference would be appreciated:</p>
<p><code>Treatment</code> is a factor with 6 levels. <code>Trial</code>... | 69,720 |
<p>I have a set of variables that parameterize a logistic equation bacterial growth model. The parameters change based on temperature (e.g., growth speeds up at higher temperatures) and so it is necessary to fit some secondary models in order to be able to estimate growth under a variety of temperatures. Only five temp... | 69,721 |
<p>After searching for this question, I did find <a href="http://stats.stackexchange.com/questions/6067/does-an-unbalanced-sample-matter-when-doing-logistic-regression">this</a> -- but it didn't seem to be asking the same question and I'd like to extrapolate on it if possible to get more into fixing it generally and th... | 30,327 |
<p>I am comparing the rate of specific Response Patterns A through L among students in Group 1 vs. Group 2 (rates for the first five patterns are exemplified in the table). These are response patterns that a research assistant and I coded from student interviews. I also created a code for Multiple Patterns, as I wan... | 69,722 |
<p>Below I show two equivalent ways to write a mixed model in R and SAS. The two R models as well as the two SAS models yield the same estimates of the random and fixed effects and the same standard errors of the estimates of the fixed effects. But the two SAS models do not give the same confidence intervals of the fix... | 69,723 |
<p>Consider two real-valued random variables $Y_1: \Omega \rightarrow \mathbb{R}$ and $Y_2:\Omega \rightarrow \mathbb{R}$. Even if they have the same domain and codomain, $Y_1 $ and $Y_2$ generate different $\sigma$-algebras, $\sigma(Y_1)$ and $\sigma(Y_2)$, and are defined in different probability spaces, $(\Omega, \m... | 30,329 |
<p>Here is my situation. I have a corpus of over 500,000 news. Now I need to cluster the news based on closeness in time and cosine similarity, using vector-space model and TF-IDF weights. I want to cluster the news that report the same event. Clustering performance is beyond time efficiency.</p>
<p>I think about usin... | 30,330 |
<p>I have an unbalanced panel model and I need to check it for stationarity. So, I need to perform a Unit Root test (I think I will use a Fisher Type Test?). But I am a bit confused whether
(1) I need to perform a panel unit root test separately for each variable I have in my model; or
(2) I need to perform a kind of... | 890 |
<p>I analyze the correlation between a change score in a variable A (A_t2-A_t1) that has been measured twice (A_t1; A_t2) and another variable B that has been measured once (at t1).</p>
<p>1.) Is it OK to assess whether there might be regression towards the mean by correlating the change score (A_t2-A_t1) with the bas... | 30,331 |
<p>I'm having problem understanding effect sizes in one-way MANOVA model.</p>
<p>In my case, I'm having a 13 variables which I used for clustering and then the produced <code>clusterID</code> variable with 5 levels serves as IV together with other four DVs(count measures) in one-way MANOVA model. I'm using R so my mod... | 69,724 |
<p>I have a set of observation from two parameters, let say $x$ and $y$ and then I want to make the conditional probability of $x$ for the given $y$, $p(x|y)$. So first I use <code>scipy.stats.gaussian_kde</code> to obtain the joint probability distribution of $p(x,y)$ and use <strong>normalized histogram</strong> and ... | 69,725 |
<p>I am trying to determine significant differences between groups of data using a k-nearest neighbor randomization test in R. This test basically looks for similarity amongst homogenous groups and separates them out using random clustering. In the literature, this test is called a "K-nearest neighbor (kNN) randomizati... | 69,726 |
<p>I am running a logistic regression in SPSS with a sample that uses survey weights. The sample size is 1000 and the weights are along the lines of .86 or 1.23 depending on the case. I am using the weights option in the <code>Data</code> command to weight my sample before I run my logistic regression but then I get th... | 69,727 |
<p>In his up-voted answer to <em><a href="http://stats.stackexchange.com/questions/14437/software-needed-to-scrape-data-from-graph/72974">Software needed to scrape data from graph</a></em>, <a href="http://stats.stackexchange.com/users/25283/alexey-popkov">Alexey</a> writes (with respect to the need for data scraping o... | 69,728 |
<p>There are <a href="http://stats.stackexchange.com/questions/40598/restricted-boltzmann-machines-vs-multilayer-neural-networks?lq=1">several</a> <a href="http://stats.stackexchange.com/questions/36247/how-to-get-started-with-neural-networks">resources</a> describing these types of networks, but none of them explicitl... | 69,729 |
<p>Generally, the sign test is used to test the hypothesis that the difference median is zero between two continuous distributions (<a href="http://en.wikipedia.org/wiki/Sign_test" rel="nofollow">Sign test</a>).</p>
<p>I am trying to understand whether it can be adapted to prove that the values from one distribution a... | 69,730 |
<p>I would like to make an enquiry regarding the use of ML or REML for GLMM. At the moment, I'm focusing on doing model selection to evaluate the effect of four fixed effects and one random effect on a response variable (continuous data) in a study of behavioural ecology. My global model is close to a Gaussian distribu... | 69,731 |
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