question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I got a slight confusion on the <a href="http://en.wikipedia.org/wiki/Backpropagation" rel="nofollow">backpropagation</a> algorithm used in <a href="http://en.wikipedia.org/wiki/Multilayer_perceptron" rel="nofollow">multilayer perceptron</a> (MLP).</p>
<p>The error is adjusted by the cost function. In backpropagati... | 32,278 |
<p>I am fitting a stepwise logistic regression on a set of data in SPSS. In the procedure, I am fitting my model to a random subset that is approx. 60% of the total sample, which is about 330 cases.</p>
<p>What I find interesting is that every time I re-sample my data, I am getting different variables popping in and ... | 73,953 |
<p>Consider the following model </p>
<p>$Y_i = f(X_i) + e_i$</p>
<p>from which we observe n iid data points $\left( X_i, Y_i \right)_{i=1}^n$. Suppose that $X_i \in \mathbb{R}^d$ is a $d$ dimensional feature vector. And suppose that a ordinary least squares estimate is fit to data, that is,</p>
<p>$\hat \beta = {\rm... | 73,954 |
<p>I need to cluster units into $k$ clusters to minimize within-group sum of squares (WSS), but I need to ensure that the clusters each contain at least $m$ units. Any idea if any of R's clustering functions allow for clustering into $k$ clusters subject to a minimum cluster size constraint? kmeans() does not seem to... | 73,955 |
<p>The underlying model of <a href="http://en.wikipedia.org/wiki/Partial_least_squares_regression">PLS</a> is that a given $n \times m$ matrix $X$ and $n$ vector $y$ are related by
$$X = T P' + E,$$
$$y = T q' + f,$$
where $T$ is a latent $n \times k$ matrix, and $E, f$ are noise terms (sssuming $X, y$ are c... | 36,545 |
<p>I think that after apply PCA the covariance between components is reduced since the aim of PCA is to maximize variance. Covariance is needed by Factor analysis and thus it does not make sense to operate on the data in PCA space. </p>
<p>Does this make any sense? Does someone have any other explanation? </p> | 48,195 |
<p>Suppose ($h_1,h_2,...,h_n$) is an $n\times 1$ vector.</p>
<p>Let $h_i=g_iX_i$, where $g_i$ is a non-random variable which can vary across $i$ and $X_i$ is a random variable with Pareto Type I distribution.</p>
<p>$$f_X(x) =
\begin{cases}
{\alpha x_m^\alpha \over x^{\alpha +1}}, & \text{if $x\ge x_m$} \\[2ex]
... | 37,291 |
<p>I’ve approached a unique problem, and I want to make sure that I am going about the test that I am running in the correct way. Here’s a brief background: The goal of this project is to automate an advertisement system, and the goal of my question is to determine the p-value that one type of advertisement has a lower... | 73,956 |
<p>I have independent observations $Y_1, Y_2, ...., Y_n$ that take values 1 or 0 with </p>
<p>$$P(Y_i = 1) = \frac{1}{1 + \exp\{-(\alpha + \beta x_i)\}}$$</p>
<p>where $\alpha$ and $\beta$ are unknown constant and $x_1, x_2, ....,x_n$ are known, I have to show that $(\sum Y_i,\sum x_i Y_i)$is a minimal sufficient sta... | 37,292 |
<p>I am using MATLAB's <a href="http://www.mathworks.com/help/stats/ranksum.html" rel="nofollow">ranksum</a> function with the computation <code>method</code> of the p-value set to <code>approximate</code>. Is there a way to determine with what precision the approximation is being made?</p> | 73,957 |
<p>I find that simple data analysis exercises can often help to illustrate and clarify statistical concepts. What data analysis exercises do you use to teach statistical concepts? </p> | 36,548 |
<p>I have a set of observations, independent of time. I am wondering whether I should run any autocorrelation tests? It seems to me that it makes no sense, since there's no time component in my data. However, I actually tried serial correlation LM test, and it indicates strong autocorrelation of residuals. Does it make... | 73,958 |
<p>For my classification problem, I am trying to classify an object as Good or Bad. I have been able to create a good first classification step that separates the data into 2 groups using SVM. </p>
<p>After tuning the parameters for the SVM using a training/holdout set (75% training, 25% holdout), I obtained the follo... | 36,549 |
<p>I am fitting a <em>Fixed-Effects</em> model, with intercepts at <code>cluster</code> level.</p>
<p>One of the most direct ways is probably to use the <code>-plm-</code> package. Another well-known possibility is to apply OLS (i.e. to adopt <code>-lm-</code>) to the <em>demeaned data</em>, where the means are taken ... | 73,959 |
<p>I have a categorical variable called Torture (=0, torture frequently used by government; =1 often used; 2=never used). Regression of economic INefficiency on torture yields negative coefficient sign.</p>
<p>Does that mean that improvements in torture (i.e., going from 0 to 2) bring down and reduce economic ineffici... | 36,554 |
<p>Not sure if this is as complicated as it's ended up in my head, here goes.</p>
<p>I have a series of measurements which measure how risk-prone psychiatric patients are (hereafter referred to as HCR and it's an interval, normally distributed outcome). These measurements come from five different locations within the ... | 73,960 |
<p>Let's say I want to implement an algorithm based on a paper or book and publish it under a non-proprietary but not necessarily non-commercial-friendly license (e.g. on a blog).</p>
<p>Is it legal to do this? </p>
<p>I know that a general all covering answer cannot be either yes or no, so I want to know additionall... | 73,961 |
<p>I'm using Holt Winters to predict sales revenue from past performance. Seasonality and changing trends exist in the data. </p>
<p>One of the reasons chosen for Holt Winters is that it is fairly simple (implementable in excel) and explainable to non-statisticians. If other methodologies are more appropriate I’m happ... | 73,962 |
<p>How can I do plot a waffle chart as an alternative to using piecharts in R?</p>
<pre><code>help.search("waffle")
No help files found with alias or concept or title matching ‘waffle’
using fuzzy matching.
</code></pre>
<p>The closest I found googling out there are mosaicplots.</p> | 73,963 |
<p>I'm trying to build a predictive model to forecast the residual value of used electronic equipment. As a first step, I created a few quick plots in order to visually identify any interesting features. Here's an example:</p>
<p><img src="http://i.stack.imgur.com/F360n.png" alt="used prices for a used consumer electr... | 36,558 |
<p>I was working with SVR, and wondering, why can't I solve a natural regression problem as a multiclassification task ?</p>
<p>Example:
I have for a regression problem: targets 1, 5 and 10, trying to fit Integers numbers inside of this range.</p>
<p>Why can't I use a multiclassification with targets 1, 2, 3, 4, 5, ... | 29,313 |
<p>Is there a way to find the Spearman correlation between two Weibull distributions? I need it as a parameter in a copula function for the joint Weibull distribution.</p>
<p>I learned that using the Pearson correlation, which I can easily obtain from the variances and cross variances of the given spectra, is not reli... | 73,964 |
<p>I am interested in estimating how many subjects should be included in a brain imaging study. Although the design is a fairly straight forward cross-sectional comparison, there are a number of tweakable image processing steps between the raw image and the processed image in which we carry out pixel-wise comparisons.<... | 36,560 |
<p>I would like to estimate an ordinary least squares regression of the form
$$
y = X\beta + \varepsilon, \
$$
except that, instead of minimizing the sum of squared residuals,
$$
SSR(b)=(y-Xb)'(y-Xb)
$$
I want to minimize
$$
(y-Xb)'(y-Xb)+\lambda(b-\tilde{\beta})'(b-\tilde{\beta})
$$
where $\lambda$ i... | 73,965 |
<p>If $\text{P}(M|D)$ is posterior, $a$ is the proportionality constant, $\text{P}(M)$ is the prior and $\text{P}(D|M)$ is the likelihood. I have the the prior distribution, and I know the function that can give the likelihood for any input parameter sample. Then the Bayes rule is:
$\text{P}(M|D)= a\times\text{P}(M)\ti... | 73,966 |
<p>which is the % of population with vote rights(above 18yo for example). Can u point me to some papers which talks about voting and ages?</p> | 73,967 |
<p>Here's an <a href="http://stats.stackexchange.com/a/66358/27996">answer</a> from one of the questions in the newsletter. I'm not trying to suggest that it's incorrect, I just don't understand why it's an acceptable practice. I know that simplifying assumptions are made all the time, but why is this useful?</p>
<p... | 73,968 |
<p>I am designing a questionnaire to compare user experience of usage of a two prototypes of a software - prototype A and B. Users will rate prototype A for a task and then prototype B for performing the same task based on a 5 point Likert scale. The questionnaire will contain 5 questions related to the various measure... | 73,969 |
<p>I'm currently working on a logistic regression problem with case-control response variable and SNP genotype as regressor. Can I treat 0, 1, 2 as continuous instead of factor? </p> | 36,564 |
<p>I have this confusion related to two methods to add gaussian white noise to data. </p>
<p>Suppose I have a bivariate gaussian distribution with mean vector and covariance matrix
$$
\mu = \begin{pmatrix} 0 \\ 0 \end{pmatrix}, \quad
\Sigma = \begin{pmatrix}1 & 0.5 \\0.5 & 1 \end{pmatrix}.
$$
Now suppose I wa... | 73,970 |
<p>I have been trying to quantify the heterogeneity of a given variable. I'd like to say that the distribution in calcite concentrations, for example, is more heterogeneous in one rock formation than another. </p>
<p>So far I've graphed and compared the variable distributions with overlain histograms and box plots for... | 73,971 |
<p>I am reading Klein and Manning's <a href="http://www.cs.berkeley.edu/~klein/papers/maxent-tutorial-slides.pdf" rel="nofollow">notes</a> on Maximum Entropy for Natural Language Processing. On slide 22, they have an equation saying,
$P(C|D,\lambda) = \Pi _{(c,d)\in (C,D)} P(c|d,\lambda)$. I am not sure how they obtai... | 73,972 |
<p>Does anyone know if adaptIntegrate accepts a vectorized integrand?</p>
<p>for e.g.</p>
<p>alpha<-c(1,2)</p>
<p>f <- function(z){
(z[1]+z[2])*alpha
}</p>
<p>adaptIntegrate(f,lower=c(1, 3), upper=c(2, 4),tol=0.01) ##does not work</p>
<p>Is what I want possible with adaptIntegrate? </p>
<p>Thanks in advance... | 36,566 |
<p>I am building a program to predict the score in a game of twenty20 cricket. I have a series of 3D datapoints, calculated from a number of games I have data for.</p>
<p>Along the x axis we have number of wickets a team has lost. Up the y axis we have number of runs they end up scoring. And in the z axis we have numb... | 37,933 |
<p>I am attempting to explain a dichotomous outcome variable using a large set of continuous valued sensor-derived variables. Many of these variables are highly mutually correlated, some are based on solid physical concepts (and therefore easier to interpret) others are more abstract and difficult to explain.</p>
<p>I... | 73,973 |
<p>I currently have data corresponding to how often a certain set of songs were downloaded. Each song has a release date, and then the number of downloads per day going forward to today. It would look like:</p>
<pre><code> Song1 Cumulative Sum of Song1
Release Date 5/7/2013 ... | 73,974 |
<p>I have tried asking this on another forum, but after 4 months there are no posted answers, so I am asking it here:</p>
<p>What is the current state of the art approach for determining the pose of a person (including close poses like a head shot, and hand shot, etc...), and for segmenting the person from the backgro... | 38,171 |
<p>I have a control condition <strong>A</strong> and several other conditions (<strong>B</strong>, <strong>C</strong>, <strong>D</strong>, etc.) against which I want to test <strong>A</strong> for differences (i.e. <strong>A</strong> vs <strong>B</strong>, <strong>A</strong> vs <strong>C</strong>, <strong>A</strong> vs... | 48,224 |
<p>I am in the process of working through the Udacity course Intro to Inferential Statistics. In Lesson 9: Hypothesis Testing, the following example is given.</p>
<p>Say that we record survey data from all students of this Udacity course detailing how engaged they are by the lecture materials. We find that the populat... | 73,975 |
<p>Let $y$ be a binary variable and $x$ be a covariate measured with known heterogeneous measurement error:</p>
<p>$x_{i}$ ~ $\operatorname{Normal}(x^{*}_{i},\sigma_{i}^{2})$.</p>
<p>Now suppose the relationship with the true covariate $x^{*}$ is $\ Y$ ~ $\operatorname{Bernoulli}(p_i) $ and $\ \operatorname{logit}( p... | 73,976 |
<p>I am using R for last 4 months with basic test analysis, regression models, ANOVA etc. Now I am looking into a particular problem. In words problem can be stated like, </p>
<blockquote>
<p>A particular machine got a problem 'ABC', what will be the
probability (with certain statistical significance - pvalue) of
... | 73,977 |
<p>I want to test whether changes in Hemoglobin (Hgb) levels over time can help diagnose Myelodysplastic syndrome (MDS).</p>
<p>I have a cohort of thousands of patients.
Each patient has several Hgb measurements over a period of 3 years.
Measurements are unevenly spaced and few (anything from two to 4 measurements).<... | 36,573 |
<p>I am working on data prediction. Given data of a random variable $X$ and $Y$, find out how to predict $Y$ from $X$. I know how to do it by linear regression, $\hat{Y} = kX + b$.</p>
<p>But, here, $X$ is always non-negative and $Y$ is required to be non-negative. Sometimes, $b$ is not non-negative so that $y < 0$... | 73,978 |
<p>I have a model with two layers. There are 4 variables with random coefficients in the second layer of the model, which is a multivariate Logit. I assume the four random coefficients follow multivariate normal distribution with different variances. Some of them even have nonzero co-variances. </p>
<p>The values gene... | 73,979 |
<p>How would I go about showing that:</p>
<p>$$\sum_{i=1}^n (X_i-\bar{X})^2=\sum_{i=1}^n X_i^2-n\bar{X}^2\,,$$ (where $\bar{X}=\frac{1}{n}\sum_{i=1}^n X_i$)?</p>
<p>Thank you for your help!</p> | 36,574 |
<p>In the first time point - 75% (485 out of 646) of boys and 63% (350/555) of girls are in group A. </p>
<p>In the second time point - 80% (480/600) of boys and 45% (225/500) of girls are in group A.</p>
<p>So that is a difference of 5% for boys and 18% for girls between the two time points: </p>
<p>![Table][1]</p>... | 73,980 |
<p>I observe a sample from a distribution that I expect to be the hitting time </p>
<p>$$\tau = \inf\{t>0| X(t)>a\}$$</p>
<p>where $X(t)$ is a Lévy process with $X(0)=0$ and $a$ is some constant. $X$ is not a Brownian motion and the experimental fit to the <a href="http://en.wikipedia.org/wiki/L%C3%A9vy_distrib... | 73,981 |
<p>Wikipedia says in <a href="http://en.wikipedia.org/wiki/Binary_classification#Converting_continuous_values_to_binary" rel="nofollow">binary classification</a>:</p>
<blockquote>
<p>Tests whose results are of continuous values, such as most blood
values, can artificially be made binary by defining a cutoff value,... | 43,363 |
<p>I'm having some trouble with overfitting in pLSA (Probabilistc Latent Semantic Analisys).</p>
<p>I'll use the following notation:</p>
<ul>
<li>$t \in T$: topic, the latent variables</li>
<li>$d \in D = D_{train} \cup D_{test}$: documents</li>
<li>$w \in W$: terms</li>
</ul>
<p>Each document $d$ is a vector of $|W... | 43,365 |
<p>I have five point likert scale responses ((1-most imp, 5-least imp) for 14 items that I want convert them into 5 factors with confirmatory factor analysis. I already have designed which item should go into what factor, so I can't use exploratory FA. Once I get the factor scores, I will use them in a logistic regress... | 73,982 |
<p>I am trying to detect convergence of a random walk on a graph. After doing some preliminary research, the Geweke convergence diagnostic seems to be most commonly used for this.
This diagnostic calls for the z-score of the chain at each iteration of the walk and declares convergence when the z-score falls within an i... | 73,983 |
<p>I understand the basic principle behind the algorithm for LLE consists of three steps.</p>
<ol>
<li>Finding the neighborhood of each data point by some metric such as k-nn.</li>
<li>Find weights for each neighbor which denote the effect the neighbor has on the data point.</li>
<li>Construct the low dimensional embe... | 73,984 |
<p>Suppose we have $V \sim W_p(n-1,\sigma^2 I)$</p>
<p>In order to find the moments of the Mauchly sphericity statistic $\Lambda = \frac{|V|}{(tr(\frac{V}{p}))^p}$ i read one can split it defining $\Lambda_1 = \frac{|V|}{v_{11}...v_{pp}}$ and $\Lambda_2 = \frac{v_{11}...v_{pp}}{(tr(\frac{V}{p}))^p}$ and then using $E[... | 73,985 |
<p>(I am far from an expert in the field of statistics, so I apologize beforehand if my question is irrelevant or my use of any terms is incorrect)</p>
<p>Let's suppose that we have a <em>discrete</em> variable $X$, and a set of $n+1$ observations $\{x_0, x_1, \dots, x_n\}$. The values of $X$ may not be numeric and al... | 73,986 |
<p>A uniform prior for a scale parameter (like the variance) is uniform on the logarithmic scale. </p>
<p>What functional form does this prior have on the linear scale? And why so?</p> | 36,598 |
<p>In SPSS Version 19 there seems to be a new feature called Automatic Linear Modelling. It creates a 'Model' (which is new to me) and the function seems to combine a number of the functions that is typically required for prediction model development.</p>
<p>The functionality seems incomplete with only a subset of pr... | 73,987 |
<p>As a basic question in Regression Analysis, I wanted to ask how can I calculate Margin of Error when I fit a straight line to a set of data.
Assume that I have variation of parameter $A$ as a function of parameter $B$, then $A=mB \pm e$, where $m$ is the tangent of the fitted straight line and $e$ is what i'm lookin... | 73,988 |
<p>You can have data in wide format or in long format.
This is quite an important thing, as the useable methods are different, depending on the format.
I know you have to work with <code>melt()</code> and <code>cast()</code> from the reshape package, but there seems some things that I don't get.</p>
<p>Can someone giv... | 49,580 |
<p>If I have values for <code>sensitivity</code> and <code>specificity</code> for a group of studies, for example like this:</p>
<pre><code>sensitivity specificity
----------- -----------
66.3 74.7
87.2 65.9
56.4 76.4
79.5 94.3
</code></pre>
<p>How can ... | 73,989 |
<p>Does anyone know how to use (nlme)? I'm having a lot of problems using it for something that should be really simple, any help would be really appreciated. I won't put up the details until I know someone knows what I'm talking about.</p>
<p>Data was collected by a field study concerned planting pattern, genotype, w... | 48,260 |
<p>I wish to simulate from a normal density (say mean=1, sd=1) but only want positive values.</p>
<p>One way is to simulate from a normal and take the absolute value. I think of this as a folded normal.</p>
<p>I see in R there are functions for truncated random variable generation. If I simulate from a truncated no... | 73,990 |
<h3>Experiment</h3>
<p>Let say I have a black box full of numbered balls and I draw them with replacement - so the propability of drawing one specific number in N draws is described by binomial distribution?
Problem is that my black box has some intristic structure so the balls are not draw with the same p.
For random... | 36,602 |
<p>I have two devices, and I'm trying to figure out which one of them is preferred by users.</p>
<p>Thirty people have rated each device on a 12-item questionnaire which asks them to grade the device on 12 parameters.</p>
<ul>
<li>What statistical tool should I use to decide which device is better? (just comparing th... | 627 |
<p>I am estimating a structural equation model in which two latent variables (with 4 indicators each) and the interaction between the two latent variables predict a single observed variable. I would like to save the individual residuals from the observed endogenous variable to use in further analyses. As far as I can t... | 48,263 |
<p>I am currently using the simple slope analysis to examine the significant interaction effects between my continuous moderator and a dichotomous predictor (values 1 & 2)on a continuous DV. I have 2 continuous covariates in the analysis. </p>
<p>My simple slope graph however showed negative values in the DV (i.e:... | 73,991 |
<p>I'm doing a project on dog adoption patterns, and I realized that there are many (100 +) different breeds of dogs. I'd like to build a predictive model using breed as covariate, but I'm not sure whether I should turn each breed into a dummy variable and run a quick and dirty supervised learning algorithm, or try to... | 73,992 |
<p>I am trying to use urca library to do cointegration test, and its function ca.jo, which conducts the Johansen procedure on a given data set.</p>
<p>I think a lag order of 1 is possible for a cointegrated VECM, which means it does not have short term error correction. For example, we have VAR(1)</p>
<p>$$
X_t=\Pi_1... | 36,607 |
<p>My R square from cox regression is about 0.02, Does it tell me that model is doing really bad?</p>
<p>I used coxph in R.</p> | 73,993 |
<p>I'm still toying with things and just learning this, so please forgive any incorrect terminology.</p>
<p>My toy data set is a collection of recipes with a fairly significant overlap in ingredients. I'm using these as my features, and using Pearson squared distance as described in <em>Programming Collective Intellig... | 37,304 |
<p>I have 3 experiments, where some quantity was measured 3 times. Thus, 3 biological replicas, 3 technical replicas in each biological replica, 9 measurements in total. I need to answer the following questions:</p>
<ol>
<li>For each biological replica: are my 3 measurements consistent? To do this, I'm using Dixon's Q... | 73,994 |
<p>I am doing a project with Weka with clustering algorithms (simple k-means, expectation-maximization and OPTICS). I would love to be able to call those algorithms over the internet. </p>
<p><strong>So does Weka has a online API?</strong> But I suspect there is no. In that case, <strong>what are the alternatives?</st... | 73,995 |
<p>I have a dataset with a large number of Yes/No responses. <strong>Can</strong> I use principal components (PCA) or any other data reduction analyses (such as factor analysis) for this type of data? Please advise <strong>how</strong> I go about doing this using SPSS.</p> | 73,996 |
<p>I am setting up a linear analysis of a single continuous dependent variable, with multiple (up to 11!) continuous independent variables. I am interested in doing something like an ANCOVA that will show the relative contribution and co-variation among the variables. But my understanding is that ANCOVA requires having... | 36,614 |
<p>I'm trying to use SAS from more of a machine learning perspective than a pure stats perspective. I want to perform resampling on a dataset to measure the predictive accuracy of a LDA and Logistic Regression. However, when I perform <code>proc logistic</code> or <code>proc discrim</code> all SAS seems to output is a ... | 36,615 |
<p>I've never had a course in statistics, so I hope I'm asking in the right place here.</p>
<p>Suppose I have only two data describing a normal distribution: the mean $\mu$ and variance $\sigma^2$. I want to use a computer to randomly sample from this distribution such that I respect these two statistics.</p>
<p>It'... | 32,753 |
<p>I have heard the following expression before:</p>
<blockquote>
<p>"Optimization is the root of all evil in statistics".</p>
</blockquote>
<p>For example, the top answer in <a href="http://stats.stackexchange.com/a/61549/2798">this thread</a> makes that statement in reference to the danger of optimizing too aggre... | 73,997 |
<pre><code>> age <- c(1,2,3)
> weight <- c(4,5,6)
> p <- data.frame(age=age, height=height)
> p
age height
1 1 4
2 2 5
3 3 6
> p[p$age > 1,]
age height
2 2 5
3 3 6
> age
[1] 1 2 3
> age.df <- data.frame(age=age)
> age.df
age
1 1
2 2... | 73,998 |
<p>I am looking into using LexRank to do some text summarization. I am looking at the <a href="http://www.cs.cmu.edu/afs/cs/project/jair/pub/volume22/erkan04a-html/erkan04a.html" rel="nofollow">original paper</a>. One thing that puzzles me is whether a damping factor is used or not. The formulae are all using it, but t... | 73,999 |
<p>Could somebody explain why ridge regression does not perform feature selection although it makes use of regularization? So, it penalizes the regression coefficients like LASSO does, but how come we end up with using all features for all the lambda (penalty) values in range? Why don't we end up getting some zero coe... | 74,000 |
<p>In a test, permutation test is used to estimate the null distribution of the test statistic from the sample.</p>
<p>In multiple comparison, what is the usage of permutation test?</p>
<p>Thanks!</p> | 74,001 |
<p>The most common methods I've seen to find a line of best fit are Least Squares regression and median-median. Are there other good ways? Is there a way to minimize the absolute value difference and find a line of best fit that way? Or to find the distance straight to a line instead of the vertical distance to the lin... | 74,002 |
<p>I try to implement Unscented Kalman Filter. Everything seems to be done correctly but I do receive an error about Cholesky decomposition</p>
<pre><code>raise LinAlgError('Matrix is not positive definite - '
numpy.linalg.linalg.LinAlgError: Matrix is not positive definite - Cholesky decomposition cannot be compu... | 36,618 |
<p>I'm looking to quickly get smart on how to add personalization into a Bayesian-based recommendation system. </p>
<p>I'm using clickstream data and Bayesian statistics to estimate probabilities of purchase to rank a list of products on. How do I incorporate user-specific history to modify my generic probabilities ... | 74,003 |
<p>First I should explain what I did, and it might not be right.
I have a variable that represents a test outcome, it might be positive or negative. </p>
<ul>
<li><p>I have a set of observations of one important variable (my point of interest) for the last 5 days before the test was undertaken. I have computed the av... | 74,004 |
<p>I have run two psychological experiments. The dependent variable is a rating provided by the participant, that is, an integer number from 0 to 100. </p>
<p>The first experiment is a mixed 2x2 design, with one between-subject factor (treatment) and one within-subject factor (question). Each of these factors has two ... | 74,005 |
<p>I am trying to find a model for the data below. I cannot decide whether the data is stationary or not. I do not want to take differences unnecessarily . I put results of the models below. I think ARIMA(0,1,3) is best model because AIC is lowest .What do you think?</p>
<p><img src="http://i.stack.imgur.com/dDBI0.pn... | 74,006 |
<p>I have microarray data in which there are three biological replicates for each of the conditions. I am interested in a numerical estimate of how well the replicates correspond with one another, so I thought I should look at variance. I suppose I could calculate it individually for each probe, but I thought there mig... | 74,007 |
<p>I've been researching the Bayesian take on classical statistics lately. After reading about the Bayes factor I've been left wondering if power analysis is a necessity in this view of statistics. My main reason for wondering this is the Bayes factor really just appears to be a likelihood ratio. Once it's like 25:1 it... | 36,619 |
<p>I am running an ordinal regression in SPSS. I have independent variables on nominal and ordinal scales. My dependent variable is ordinal, indicating a level of action, coded 0, 1, 2. Unfortunately, I currently don’t know how to deal with the non-significance of a threshold level for my dependent variable indicated b... | 36,621 |
<p>Hi I am looking for a robust convex optimization problem solver in python. My problem isn't very complex, its basically a simple constrained qp program. I am using Enthought free python 2.7 distribution on a windows 64 bit machine. </p>
<p>I came across <a href="http://cvxopt.org/install/index.html" rel="nofollow">... | 36,622 |
<p>For example: An initial set $[1, 3, 4, 7, 2]$ sums to 17. By dividing each element by the sum, the elements sum to 1: $[1/17, 3/17,...2/17]$ sums to 1.</p>
<p>What is it called when a set of numbers are adjusted to sum to one? </p> | 74,008 |
<p>According to Wikipedia, the <a href="http://en.wikipedia.org/wiki/G-test" rel="nofollow">G-test</a> statistic is "proportional to the Kullback–Leibler divergence of the empirical distribution from the theoretical distribution." To get the relationship between $ G $ and the KL divergence:
$$
\begin{align*}
G &= 2... | 74,009 |
<p>I have great difficulty in calculating $\mathrm{E}\left(T_{1} T_{2}^{-1}\right)$ where $T_{i}$ is a random variable distributed according to the <a href="https://en.wikipedia.org/wiki/Birnbaum%E2%80%93Saunders_distribution" rel="nofollow">Birnbaum-Saunders distribution</a>. Are there any suggestions on how to calcu... | 74,010 |
<p>I read that there is a bias when we transform a series with a logarithm and then applying the inverse function, but only in forecasts of the mean values.</p>
<p>I don't understand what it means exactly. </p>
<p>In the book "Introductory Time Series with R", there is a section about this very issue:</p>
<blockquot... | 74,011 |
<p>I have collected data where respondents provide on of the following responses</p>
<pre><code>1. non interested to be involved
2. only get information on the topic but not participating
3. consulting on the topic
4. taking responsibility
</code></pre>
<p>for each each of the following four topics</p>
<pre><code>1.... | 74,012 |
<p>I have a dataset in which I measure the response variable of a number of individual animals. I used this response variable as the dependent variable in a linear mixed model, for which I have 5 explanatory variables. Two of these explanatory variables are nested if they are entered in the same model, as they refer to... | 74,013 |
<p>I am a PhD student with some difficulties about what test to choose to verify an experiment. Hope you can give me some help!</p>
<p>My experiment:
I am counting the number of a subset of cells in Drosophila overtime.
I have a mutant and a wild type control. I dissect the flies at different time points: just eclosed... | 36,634 |
<p>I have a questionnaire where some of the questions concern ranges, the answer alternatives are:</p>
<ul>
<li>0</li>
<li>1 - 15</li>
<li>16 - 30</li>
<li>31 - 45</li>
<li>46 - 60</li>
<li>60+</li>
</ul>
<p>(the numbers are minutes per week, not that it matters)</p>
<p>If I would like to present the result as an av... | 74,014 |
<p>What are the best (recommended) pre-processing steps before performing k-means?</p> | 74,015 |
<p>I am so puzzled by this problem. </p>
<p>Given two variables $X_1$ and $X_2$, such that $X_i \sim \mathrm{Gam}(a_i, b)$, find the joint distribution of $X_1$ and $X_2$. </p>
<p>I understand how to proceed if variables are independent, but the general case is a bit unclear.
Thanks for your help! </p> | 48,297 |
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