question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>The library languageR provides a method (pvals.fnc) to do MCMC significance testing of the fixed effects in a mixed effect regression model fit using lmer. However, pvals.fnc gives an error when the lmer model includes random slopes. </p>
<p>Is there a way to do an MCMC hypothesis test of such models?<br>
If so, ... | 31,048 |
<p>I am looking for help phrasing/reporting the results of a Generalized Linear Model. I have received some feedback that my current format is difficult to understand. I have multiple predictor variables and I repeatedly use the phrasing like "[predictor 1] was a significant predictor of [x]". "[Var 1] interacted signi... | 70,220 |
<p>The data I have is 20 sampling points in a water distribution network that have been sampled weekly during 4 months for different parameters (chlorine, turbidity, disinfection by-products, ...). Some parameters were measured once per week while others were measured three times (Morning/Midday/Evening) in a sampling ... | 31,050 |
<p>I've implemented a basic perceptron with a Heaviside activation function, and learned weights for a toy 2D data set with four instances.</p>
<p>The training instances and their labels are the following, where the first element is a bias term:</p>
<pre><code>X = np.array([
[1, 0, 0],
[1, 0, 1],
[1, 1, 0... | 70,221 |
<p>I am slightly confused by the the statement that <a href="http://en.wikipedia.org/wiki/Kullback%E2%80%93Leibler_divergence" rel="nofollow">Kullback–Leibler divergence</a> is the same as [information gain](Information gain in decision trees).</p>
<p>I cannot understand how $D_{KL}(P||Q) = H(P,Q)- H(P)$ can be repres... | 70,222 |
<p>As said in the title, what would non-ergodicity mean for Bayesian satistics, and if the process being investigated is non-ergodic, how would Bayesian methods tackle this process - would it be different from ergodic case or not?</p>
<p>So in classical(frequentist) statistic, if the world investigated is stochastic p... | 31,053 |
<p>We all know the mantra "correlation does not imply causation" which is drummed into all first year statistics students. There are some nice examples <a href="http://stats.stackexchange.com/questions/36/correlation-does-not-mean-causation">here</a> to illustrate the idea.</p>
<p>But sometimes correlation <em>does</e... | 49,340 |
<p>I have a longitudinal dataset, so for each company different year observations. The time period of the dataset is 1993 to 2008. I tested a FGLS model on the whole dataset.<br>
Now I want to test the FGLS model on three separate models (1993-1999)-(2000-2002)-(2003-2008).<br>
More specifically I want to compare the r... | 70,223 |
<p>In answering <a href="http://stats.stackexchange.com/questions/206/discrete-and-continuous" rel="nofollow">this question on discrete and continuous data</a> I glibly asserted that it rarely makes sense to treat categorical data as continuous.</p>
<p>On the face of it that seems self-evident, but intuition is often ... | 70,224 |
<p>I have a dataset with one binary target variable called “target” and many many factors “F1”, F2”… “F200”. I’m trying to come up with code to fit 200 single factor logistic regression models and return the model summaries. Here is what I have so far</p>
<pre><code>single <- function(df, factor){
s <- summa... | 70,225 |
<p>I was trying to do a test of reliability for my survey items. In addition to Cronbach's alpha I'm looking at communalities. My criteria is that survey items with communality below 0.4 will be dropped. But when I looked at my communality table, I saw that some items had .99 for communality. Is this problematic? What ... | 44,307 |
<p>After a cluster analysis I´m trying to plot for each cluster the Index plot of the Silhouette value instead of for the complete dataset
(like in the WeightedCluster Library Manual by Matthias Studer). First of all, is that theoretically correct? If yes...</p>
<p>I create the object "sil" with the wcSilhouetteObs ... | 31,057 |
<p>I am currently working on time series modeling, especially on stationarity tests. For this purpose, I am extensively using Pfaff's book "<a href="http://www.springer.com/statistics/statistical+theory+and+methods/book/978-0-387-75966-1" rel="nofollow">Analysis of integrated and cointegrated time series with R</a>" an... | 31,058 |
<p>our decision function e.g. in SVMs for binary classification (where the response is labeld by $y_i \in \{-1,1\}$) has the form:</p>
<p>$f(\mathbf{x}) = \text{sgn}(\mathbf{w}^\top \mathbf{x} + b)$ where $\mathbf{w}^\top \mathbf{x} + b =0$ is the equation of the separating hyperplane.</p>
<p>But what happens if a ne... | 31,059 |
<p>I need to calculate the MAP estimator of $ x $ in the following case:</p>
<p>$$ \left [ \begin{matrix}
{y}_{1}\\
{y}_{2}
\end{matrix} \right ] =
\left [ \begin{matrix}
x\\
x
\end{matrix} \right ] +
\left [ \begin{matrix}
{n}\\
{n}^{2}
\end{matrix} \right ] $$</p>
<p>Given the following distributions:</p>
<p>... | 30,297 |
<p>I have created 5 imputations of a dataset and have fit a survival model to them all in R. I want to combine the estimates of the coefficients and the standard errors of the coefficients. To do this I have taken the mean of the coefficients and combined the standard errors using Rubins formula, i.e.
$$(1+1/m) \times... | 47,088 |
<p>Using glm, I have fitted a model with a gamma response distribution and tested all the model diagnostics so everything looks to be a good fit. The only problem is that the model's deviances point to the inverse link function being the most appropriate, however, I not too sure how to interpret the parameters. If I w... | 31,061 |
<p>I am acquiring samples that are Gaussian distributed and I need to calculate</p>
<p>$$ p(x_n | x_{n-1}, x_{n-2}, \ldots , x_1) $$</p>
<p>for each sample $x_n$ as it comes in. I am trying to break this expression down so that I can calculate this recursively. I can not store past variables indefinitely as the syste... | 3,421 |
<p>I'm looking through my notes on importance sampling.</p>
<p>$\mu = \int h(x)\pi(x)dx = \int [h(x) \frac{\pi(x)}{g(x)}]g(x)dx$</p>
<p>draw $x^{(1)},...,x^{(m)}$ i.i.d. from proposal distribution $g(x)$</p>
<p>Calculate the importance weights:</p>
<p>$w^{(i)}=\frac{\pi(x^{(i)})}{g(x^{(i)})},$ for $i = 1,...,m$</p>... | 70,226 |
<p>I have a data set which consists of large number of data points. However, there are some outlier points that can be considered be noise. If I include all data points to approximate the Gaussian distribution, the standard deviation is apparently larger than expected. How can I fit this data set with a Gaussian distri... | 70,227 |
<p>I was reading some notes on machine learning when I came across the following sentence:</p>
<blockquote>
<p>First, we may have a large <strong>estimation error</strong>. This means that, even if
the true relationship between x and y is linear, it is hard for us to
estimate it on the basis of a small (and pote... | 70,228 |
<p>In my formula I have several terms with the categorical variable <code>color</code> and <code>color</code>'s interaction with other variables. Color can be either white or red. When looking at the summary of my model, color is replaced by colorwhite with no mention of colorred. Can someone explain the mechanics behi... | 49,846 |
<p>The book "Elements of Statistical Learning" describes Principal Components Analysis through SVD as follows:</p>
<p>$ X = UDV^T $</p>
<p>Then $ UD $ are the Principal Components and $ V $ are the directions.</p>
<p>However, later in the book, in section 14.7.1, there is also "Latent Variables and Factor Analysis":... | 70,229 |
<p>What is the significance of using conditional expectation E(Y|X=x) in regression and not just use the regular expectation E(y). What will be the consequence if we use E(Y) instead? ( can we do this since we know one of the assumptions of regression is that X is a known quantity and it is fixed). So, what is wrong he... | 70,230 |
<p>I'm working on a time series problem where the spacing between observations is usually 12 or 24 hours, but this is not guaranteed. I'd really like to estimate the auto-correlation function, and I've coded up a solution in R (shown at the bottom of this question). Basically, I'm looping through all the observations... | 31,070 |
<p>I am having trouble building my model properly, and I was hoping I could get some advice here. </p>
<p>I have a 2 (S: P vs. D) x 3 (ET: CA vs. CO vs. AD) between-subjects design. Participants were run in pairs (one P was always matched to one D and they were in the same ET condition), so I know I need to nest by pa... | 70,231 |
<p>I was on page 66 of ESL. I don't know how equation 3.49 on that page is derived. Where does the $N$ in the denominator come from ? Can someone kindly show me the steps in between the lines of equation 3.49? In particular, why is $Var(Xv_1) = \frac{d^2_1}{N}$ ? And where does the $N$ come from ? Thanks. </p>
<p><im... | 70,232 |
<p>I am aware that there is a matched-pairs t-test between two lists of counts. However, I cannot find any matched-pairs t-test of proportions. For example, list a may be [1/2, 24/30, 5/8] and list b may be [51/100, 4/9, 4/8].</p>
<p>If not, how can I go about comparing two lists like this?</p> | 70,233 |
<p>Has anyone written a brief survey of the various approaches to statistics? To a first approximation you have frequentist and Bayesian statistics. But when you look closer you also have other approaches like likelihoodist and empirical Bayes. And then you have subdivisions within groups such as subjective Bayes objec... | 31,074 |
<p>I have a few (e.g. 10) observations of travel times for a route.</p>
<p>A commuter needs to arrive to his destination before t0 (given).</p>
<p>I want to say: The commuter should depart before <code>t0 - x</code> to arrive to his destination at <code>t0</code> with probability 95%.</p>
<p>Can I do this just by ca... | 70,234 |
<p>I have three Pearson correlation coefficients (.8978, .5676 and .7865) for three age groups (i.e. 21 to 30 years, 31 to 40 years and 41 to 50 years) whose behaviour I am studying in regard to their shopping habits versus weight gain.</p>
<p>Can I say .8978 is the strongest relationship between shopping habits and w... | 49,596 |
<p>I want to predict inter-day electricity load. My data are electricity loads for 11 months, sampled in 30 minute intervals. I also got the weather-specific data from a meteorological station (temperature, relative humidity, wind direction, wind speed, sunlight). From this, I want to predict the electricity load until... | 70,235 |
<p>I have a problem with my mixed effects model where I found that both subjective evaluations of my stimuli (valence - positive or negative and self-relevance - highly self-relevant or not self-relevant) are highly correlated with one another. Theoretically this is not too surprising but poses a problem in my model. T... | 70,236 |
<p>I'm currently working on audio data trying to perform a recognition for given classes (for example grinding coffee etc.). However, I have some trouble distinguishing the null class from interesting sound segments.
Currently, I simply look at the audio intensity. As I have a limited, known number of classes I want to... | 70,237 |
<p>So I have these data points and I know the ground truth/labels of these points. I want to use Hierarchical clustering on the dataset given that all of the points that have the same labels are clustered together. I know this somewhat defeats the purpose of clustering where I use a clustering method on a dataset and c... | 70,238 |
<p>I have time series data of credit card transaction volumes for different companies. For example:</p>
<p>week1: \$5000
week2: \$6000
week3: \$6200
week4: \$7000
week5: \$9000
...</p>
<p>Is there a simple method in R to determine if the number series has a linear trend upwards, downwards or like a normal distributio... | 70,239 |
<p>I have read up on Bayesian methods enough now to feel that I would rather use Bayesian analysis over Frequentist, the trouble now is finding the correct tools...</p>
<p>I have data from an experiment with two groups of inbred fly lines and the measured variable is a continuous numeric value. Each group contains 40 ... | 70,240 |
<p>In a simple linear regression</p>
<p>$SSR = \sum(\hat{y} - \bar{y})^2$</p>
<p>$SSXY = \sum(x - \bar{x})(y-\bar{y})$</p>
<p>$SSX = \sum(x - \bar{x})^2$</p>
<p>$SSR$ can be computed by dividing $SSXY^2$ by $SSX$. Namely, $SSR = SSXY^2/SSX$</p>
<p>Could someone illustrate mathematically how this is obtained? Thank... | 70,241 |
<p>How are the results of the Spearman-Brown prophecy formula affected by having test questions of differing difficulties or raters who are easy or hard graders. One respected text says the S-B is affected, but does not give details. (See quote below.)</p>
<p>Guion, R. M (2011). Assessment, Measurement, And Predict... | 70,242 |
<p>I am checking an implementation of Logistic Regression from <a href="http://msdn.microsoft.com/en-us/magazine/jj618304.aspx">here</a>.</p>
<p>After I reading that article, it seems the important part is the find the best coefficients to determine the sigmoid function. So I just wonder why this method is called "Log... | 70,243 |
<p>Let the model be $\log(W) = a + bX + U$ where $E(U) = 0$. We are allowed to assume that $\operatorname{Cov}(X,U) = 0$, and want to show $e^{xb^\text{ols}}$-1 is a consistent estimator for $e^{xb}$-1 and it is a biased estimator for $e^{xb}$-1. We can derive that $b^\text{ols} = \frac{\sum_{i=1}^n(X_i-\bar X)Y_i}{\su... | 24,272 |
<p>Suppose we have a data set generated from k different distributions.</p>
<p>In k-means, the data classification step (in which we associate each data point to the nearest centroid) uses the current centroids to generate new data clusters. We can say that the better the centroids positions are, the better the classi... | 31,089 |
<p>Eg: In a list of three items ("1", "2", "3") the user is asked which item is higher, 1 or 2. They select 1. They are then asked which is higher, 2 or 3. They select 3. The system then reasons: "1 is higher than 2. If 3 is lower than 2 it must logically be lower than 1 also." etc.
(So that you can sort a list of ite... | 5,995 |
<p>I have this confusion related to Monte Carlo Markov Chain method. I know that Monte Carlo method is used to get the sample mean instead of calculating the high dimensional integration which is not tractable. </p>
<p>However, I didn't get what's the role of Markov chain in this. I mean if we take samples from the po... | 70,244 |
<p>To test the significance of the skewness difference between two distributions with $N_1$ and $N_2$ samples, would the following test work:</p>
<ol>
<li><p>Create a single array of all the samples from both distributions.</p></li>
<li><p>Randomly shuffle the array .</p></li>
<li><p>Split the array at index $N_1$.</p... | 70,245 |
<h2>Background</h2>
<p>I understand Monte Carlo methods only superficially, but I understand you can repeatedly randomly sample, with or without replacement, from your data set to estimate population parameters (and other things?).</p>
<p>Furthermore, I have been trying to understand, and avoid, common problems which... | 70,246 |
<p>I am applying some statistical tests using python's scipy.stats library to some datasets that I have (taken in pairs), testing whether they both come from the same unknown distribution.</p>
<p>I don't have much background in statistics, so forgive me for the following questions. I was looking at the documentation a... | 41,591 |
<p>Show that all the characteristic roots of a dispersion matrix of a random variable are non-negative.</p>
<p>$$\begin{vmatrix} \sigma_{11}-\lambda & \sigma_{12} & \cdots & \sigma_{1p}\\ \sigma_{21} & \sigma_{22}-\lambda & \cdots & \sigma_{2p} \\ \vdots & \vdots & & \vdots\\ \si... | 35,884 |
<p>We have population $Y_i = a + b X_i + e_i$ with $e_i \sim N(0,\sigma^2_e)$, but only have access to $X_i^*$ which is the real $X_i$ combined with some measurement error $u_i \sim N(0,\sigma^2_u)$.</p>
<p>I want to explore the residual variance-covariance matrix $\Sigma$ of the specification with the measurement err... | 70,247 |
<p>I am trying to calculate covariance matrix from a 2D data, assumed from coming from a Gaussian Distribution. I am trying to calculate using the equality that $\mathrm{Var}[x] = \mathrm{E}[x^2] - \mathrm{E}[x]^2$, so supposing that <code>D</code> is the data matrix where rows are observations, the MATLAB code is:</p>... | 31,096 |
<p>I'm using the generalized linear models function in SPSS with a normal distribution and identity link function. If I choose the likelihood ratio $\chi^2$ statistic, I get the same results as the Univariate GLM, which is not surprising. However if I use the SPSS's default Wald $\chi^2$, I get vastly different $\chi^... | 70,248 |
<p>What is the relation between Linear discriminant analysis and Bayes rule? I understand that LDA is used in classification by trying to minimize the ratio of within group variance and between group variance, but I don't know how Bayes rule use in it.</p> | 31,098 |
<p>I have a dataset with a categorical treatment (1 if treated, 0 if control) and many columns (34) of response variables. Each column represents a species and its response (some measured abundance) to the presence or absence of the treatment. Each row is a separate site; exactly half of them were treated and the oth... | 70,249 |
<p>I have data where a Normally-distributed outcome was collected at two time points. Covariates were also collected at both time points. Some of the covariates (e.g. sex) didn't change between the two time points.</p>
<p>I am interested in modelling the data to see whether changes in predictor variables were associa... | 70,250 |
<p>Please bear with me - I have a very limited knowledge in statistics.
Here is my case (simplified):<br>
A weather pattern is derived from 1 year of data. We are monitoring:<br></p>
<ul>
<li>sky conditions (sunny/overcast) <br></li>
<li>wind direction (E/W/N/S) <br></li>
</ul>
<p>Goal: We are trying to predict proba... | 70,251 |
<p>I am learning a regression tree for data of the form $(x_i,y_i)$:
$x_i = (1, 0, 1, ...., 1 , 1)$ a multiple input vector and $y$ is a ratio of the number of observations divided by the number of trials for that input. so $y_i = (obs/trials)$.
My problem is that most of the data is sparse, meaning that most of the i... | 70,252 |
<p>I have two answer pools for the same survey. I want to compare these answers that came from 2 different groups. Or I want to somehow see if these two groups share the same ideas about asked questions.#</p> | 70,253 |
<p>I use a CCD to see the split of a energy level due to Zeeman effect. </p>
<p>I have a 1 dimensional CCD of 7926 pixel of 7μm each one. My CCD analyze a region 2 dimensional, and then it steps forward 200 times. So, i have a matrix like this <img src="http://i57.tinypic.com/xn5f7s.png" alt=""matrix"">.</p>... | 70,254 |
<p>I have data for a few stores which sell apples. For each store I have an averaged value of how many kilos of apples users have bought per day for this month. So it looks like this:</p>
<pre><code>Store 1:
-------
January - average of 10 kilos of apples per day
February - average of 18.7 kilos of apples per day
Marc... | 70,255 |
<p>I would like to construct a quiz which has N questions (e.g. N=300) and M participants (e.g. M=1000). Each participant would be asked a subset of N questions (e.g. sub=20). In the end, for each question we would get X amount of answers from different participants.</p>
<p>How to calculate the optimal ratio of partic... | 70,256 |
<p>I would like to perform a combination of oversampling and undersampling in order to balance my dataset with roughly 4000 customers divided into two groups, where one of the groups have a proportion of roughly 15%. </p>
<p>I've looked into SMOTE (<a href="http://www.inside-r.org/packages/cran/DMwR/docs/SMOTE" rel="n... | 70,257 |
<p>I have this Bayesian network where variable C is dependent on variables A and B. I want to know how come</p>
<p>$
P(B|C) = \frac{P(B)}{P(B)+(1-P(B))P(A)}
$</p> | 70,258 |
<p>Each teeth growths from the crown to the root. There are different stages previously described to divide this process, as Crown initiation, one half of the crown, crown complete, root one quarter, root and a half, etc. Each of these stages of each different tooth (incisors, canines, molars, etc) has its own typical ... | 70,259 |
<p>I have a clinical trial phase 2 3 stage that I need a design for:
3 groups of 12 blood transfusion done at different Hemoglobin levels. It is not a dose escalation study because the transfusion is the same amount of blood for all groups.</p>
<p>I need a study design and a statistical test suggestion. </p> | 70,260 |
<p>I am trying to test some results I have for significance. It has been recommended that I use R and I am completely new to this.</p>
<h3>Set-up:</h3>
<ul>
<li>Groups: two groups of 8 subjects (16 total)</li>
<li>Two conditions: alert and passive</li>
<li>Measurements: responses for three different stimuli (A, B, an... | 70,261 |
<p>Greeting</p>
<p>I would like to know what is the impact of windowing functions like Hanning,... on a time series.</p>
<p>Is it possible to finde anomalies using windowing functions?</p>
<p><strong>EDIT</strong></p>
<p>I have a time series, which contains integer values (470,471,472,472,473,471,...) I try to find... | 70,262 |
<p>I have a small doubt in the way estimators are defined. We have a sequence of data points
$X^{(1)}, X^{(2)}, ... , X^{(n)}$. We then define an estimator as a function of these data points. When calculating the bias of an estimator we find the expectation of this function of
"random variables".</p>
<p>But are $X^{(... | 70,263 |
<p>This is a second question related to previous post:
<a href="http://stats.stackexchange.com/questions/16641/is-this-mixed-anova-correctly-specified-in-r">Is this mixed ANOVA correctly specified in R?</a></p>
<p>To reiterate, the setup is as follows:</p>
<ul>
<li>Groups: two groups of 8 subjects (16 total)</li>
<li... | 41,599 |
<p>As I understand it, matching is one way to identify causality in observational studies. By matching observations that are "similar" and comparing ones that did or did not receive treatment, you can consider this as a quasi-experiment of sorts.</p>
<p>What is overmatching? What kind of bias does it introduce? I have... | 70,264 |
<h3>Context:</h3>
<p>In a previous question, @Robbie asked in a study with around 600 cases <a href="http://stats.stackexchange.com/questions/16611/why-would-all-the-tests-for-normality-reject-the-null-hypothesis">why tests of normality suggested significant non-normality yet the plots suggested normal distributions</... | 31,107 |
<p>I am attempting to impute my data for missing values using the <code>mice</code> function (from the <a href="http://cran.r-project.org/web/packages/mice/index.html" rel="nofollow">mice</a> package) in R. However everytime I run the function it freezes or lags.</p>
<p>I have tried running it over night, and it still... | 41,601 |
<p>A/B testing:</p>
<p><a href="http://20bits.com/articles/statistical-analysis-and-ab-testing/" rel="nofollow">http://20bits.com/articles/statistical-analysis-and-ab-testing/</a></p>
<p><a href="http://elem.com/~btilly/effective-ab-testing/" rel="nofollow">http://elem.com/~btilly/effective-ab-testing/</a></p>
<p>I'... | 70,265 |
<p>I am reading de Haan's Extreme Value Theory (2006). In the discussion of distribution of sample maximum, he said "in order to obtain a non-degenerate limit distribution, a normalization is necessary". Then he gave the following example. "Suppose that there exists a sequence of constants $(a_n)>0$ and $(b_n)$ such... | 70,266 |
<p>The original question was confusing, so I've edited it to describe the core of the problem.</p>
<p>I have a large time-series (300K items) of integers between 0 and 9. Any two consecutive integers are distinct:</p>
<pre><code>0, 1, 2, 3, 0, 1, 0, 1, 0, 1, 2, 3, 4, 5, 1, 0, 1, 2, 3, 0, 1, 0, 1, 0, 1, 2
</code></pre... | 31,115 |
<p>I posted this on maths, but seems it would be better here :S</p>
<p><a href="http://math.stackexchange.com/questions/49941/calculate-the-rate-of-change">http://math.stackexchange.com/questions/49941/calculate-the-rate-of-change</a></p>
<p>Basically </p>
<p>I am trying to calculate the change frequency for a set o... | 31,116 |
<p>I'm just facing an issue of finding an easy tutorial or guide to the <code>funnel plot</code>.</p>
<p>Are there simple resources you recommend for this?</p>
<p>Thanks.</p> | 4 |
<p>I have calculate the estimates through Maximum Likelihood procedure with model of six latent variables(presented in big ellipse) with respective observed variables (presented in rectangle) in AMOS 20.0. The relationship between latent and observed variable represent factor loadings which should be greater than 0.5 i... | 70,267 |
<p>I'm trying to implement Pettitt test in R following papers like this <a href="http://www.ias.ac.in/jess/forthcoming/JESS-D-13-00049.pdf" rel="nofollow">pdf</a> (pp. 5 & 6), or this <a href="http://www.igu.in/17-3/paper-2.pdf" rel="nofollow">pdf</a>. But, I'm misunderstanding something, because having tested it w... | 70,268 |
<p>Regression discontinuity designs aren't susceptible to regression to the mean. I'm not quite sure why, though. The best I can come up with is that regression to the mean is a phenomenon that occurs because you're dealing with a sample measured at different points, which have different underlying distributions at eac... | 70,269 |
<p>I would like some help with my analysis. I have an outcome variable that represents average number of errors somebody experiences per hour. It has about 26% zeros. 85% of values are smaller than 1. There are some outliers going up to >700. </p>
<p>My explanatory variables are only categorical variables. One has 3 c... | 70,270 |
<p>I saw a paper that uses Gaussian kernel for calculation at covariance matrix of given variables. Is it mathematically Correct or not? if it is okay,what is the intuition behind ? What about using any distance function instead of Gaussian kernel? </p> | 31,120 |
<p>I wonder if there is a test for comparing means of two different time series (both measured at the same person or two different persons)?
Would be very glad if someone can help me!</p> | 49,847 |
<p>I've come across related forums, but can't seem to fit them to my problem -- I have significant interaction in a multi-level framework between a three-level categorical predictor (condition assignment - one of which is a control condition and the other two experimental conditions) and a two-level categorical predic... | 31,123 |
<p>Suppose I have 1 year of hourly streamflow values - approx. 8760 values. I am developing a model that outputs an estimated streamflow value for each of the 8760 values. I examine the sum of squared errors (for different predicted and observed outputs) and try to minimize it during calibration. What differences may... | 70,271 |
<p>How can we use Chi-Square test for categorical variables?
For example, when we have {True,False} values for the variable under test.</p>
<p>Is Chi-Square test suitable in this case? is there any other alternatives?</p>
<p>Here is an example of my data. I have two adjacency matrices {observed, expected} for the sa... | 31,124 |
<p>I am a psychology undergrad student and I'm not the best at stats. My thesis is due soon but I'm having trouble with my analysis despite extensively searching for an answer. It would be helpful to me if any answers are given in simple terms! </p>
<p>My dependent variable is victim blame and is continuous scale data... | 70,272 |
<p>Not sure what the exact term is for what I'm trying to do.</p>
<p>I have a data set with random variable x with values X1, X2, ..., XN that has a standard deviation sigma and a mean m.</p>
<p>I want to perturb the values of X1, X2, ..., XN so that the new distribution has a standard deviation of sigma' and mean m'... | 70,273 |
<p>My team manages a survey that has been reporting for many years as "relative sample error" a range of figures which are in fact the Xs in "+/- X percent" of an estimate where X is chosen to make up a 95 percent confidence interval. So in fact they are about 1.96 times the relative standard error. The users - who a... | 70,274 |
<p>I'd like to generate more than two (i.e 3) correlated series, take an example when the series follows an IMA(1,1) process, at first I want to generate three correlated random errors <code>e[i]</code> and then I use the following equation to build the series: <code>d[i,] <- mu + d[i-1,] - theta*(e[i-1,])+e[i,]</co... | 41,610 |
<p>This question is an extension of one I asked a few weeks back, here is the link:</p>
<p><a href="http://stats.stackexchange.com/questions/45820/pca-and-small-number-of-observations">PCA and small number of observations</a></p>
<p>I will restate that I am interested in the use of PCA in situations where <em>n =<... | 31,128 |
<p>I have a classifier that classifies each sample point as positive or negative. Suppose I am evaluating it on a limited data set where I have ground truth and then computing the F-measure (<a href="https://en.wikipedia.org/wiki/F1_score" rel="nofollow">F1-measure</a>). In fact, I have two classifiers, and one has a... | 18,069 |
<p>The partial SS for two factor (N and P factors) factorial experiment with interaction can be calculated as:</p>
<p>\begin{eqnarray*}
\textrm{SS}\left(N_{i}|\mu,P_{j},\left(NP\right)_{ij}\right) & = & \textrm{SS}\left(\mu,N_{i},P_{j},\left(NP\right)_{ij}\right)-\textrm{SS}\left(\mu,P_{j},\left(NP\right)_{ij... | 70,275 |
<p>I am running isomap for feature reduction and I want to see what number of features are best for classification with experiments at different number of features. Do I need to run isomap for each try to get specified number of features or just run the algo. once and chose again and again the number of features I need... | 70,276 |
<p>Considering a simple linear regression model Y= beta0+beta1 x X, with beta0 and beta1 computed, I have to estimate the expected X given a new Y and 95% confidence intervals.
I used the formula X=(Y-beta0)/slope. How can I compute in R the 95% interval for the calculated value of ind, given a new value of the height... | 70,277 |
<p>I'm trying to analyze data that violates the assumptions of an ANOVA (homogeneity of variances), thus I think I have to conduct a non-parametric test. My study follows a factorial completely randomized design:
3 sources
4 treatments
4 replicates per treatment*source combination (replicates are equal in size)</p>
<p... | 47,489 |
<p>I have a cross-over design where a sample of subjects undergoes 7 different interventions, and within each intervention there are 3 time points (pre-intervention, post-intervention1, post-intervention2).</p>
<p>I firstly did an overall ANOVA with factors time x intervention, to check whether there were overall diff... | 70,278 |
<p>Short question: How does the calculation and interpretation of IRT item information and test information change in the presence of item properties?</p>
<p>Long question: There's a variation on IRT called the linear logistic test model (LLTM):</p>
<p>$logit(Y_{p,j}) = \theta_p + \sum_{k=1}^K q_{j,k} \alpha_k$</p>
... | 70,279 |
<p>I have a table includes the following data:</p>
<pre><code>Status | Age | Tenure | Function | Gender | Race | Grade Level
-----------------------------------------------------------------
Active | 34 | 1.2 | PSO | Female | White| 26
Terminated | 24 | 0.2 | Finance | Male | Asian| 32
Active ... | 70,280 |
<p>I have a discrete random variable $X$ and two random vectors $\vec{Y}$ and $\vec{Z}$.</p>
<p>For a given $x$ (i.e. an instance of $X$), I am interested in estimating:</p>
<p>$$E[\vec{Y} \vec{Z}^{\top} | X = x]$$</p>
<p>based on samples $(x_1,y_1,z_1),\ldots,(x_n,y_n,z_n)$.</p>
<p>I thought of using a kernel esti... | 47,498 |
<p>Can you please provide with me with the names of the most important journals in data mining, machine learning, natural language processing and information retrieval?</p> | 31,133 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.