question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I am reading the Hidden Markov Model note <a href="http://cs229.stanford.edu/section/cs229-hmm.pdf" rel="nofollow">http://cs229.stanford.edu/section/cs229-hmm.pdf</a> from Stanford and have problem finding the meaning of the notation described below.</p>
<p>What does the semicolon (;) means in below (Page 2 in abov... | 49,858 |
<p>It seems that WinBUGS has problems <strong>if it has only zero draws from one binomial distribution</strong>:</p>
<p><strong>1. case - simple model</strong></p>
<pre><code>for (i in 1:sites) {
N[i] ~ dpois(lambda)
for (j in 1:sample) {
y[i, j] ~ dbin(p, N[i])
}
}
</code></pre>
<p>If all values... | 74,349 |
<p>When given samples of a discrete random variable, the entropy of the distribution may be estimated by $- \sum \hat{P_i} \log{\hat{P_i}}$, where $\hat{P_i}$ is the sample estimate of the frequency of the $i$th value. (this is up to a constant determined by the base of the log.) This estimate should not be applied to ... | 37,205 |
<p>I want to run ordinal logistic regression (OLR) in SPSS. My data include 6 predictor variable (two continuous and 4 categorical ) but my outcome variables are also 6 (categorical-likert scale).
e.g my dependent variable is Business development and 6 likert scale questions were asked for this, increase in profit, sal... | 74,350 |
<p>I am doing some basic fitting of data and exploring different fits. I understand that the residual is the difference between the sample and the estimated function value. The norm of the residuals is a measure of the deviation between the correlation and the data. A lower norm signifies a better fit.</p>
<p>Suppose... | 74,351 |
<p>I am working on an assignment for a course in statistics, and a part of the assignment is to give the null hypothesis of an experiment. The experiment is as followed (short summary):</p>
<p>A company is testing 3 interfaces for a website. They test the interfaces with 15 students, 5 for each interface, and all 5 ha... | 37,210 |
<p>When I want to apply an ARIMA model like this:</p>
<pre><code>arimax(dataMat, order=c(7,0,0), xreg=xreg)
</code></pre>
<p>it raises an error </p>
<blockquote>
<p>"singular and could not compute QR decomposition of Hessian" for xreg.</p>
</blockquote>
<p>How can I fit proper model by using <code>xreg</code> val... | 74,352 |
<p>I am doing a two-way independent ANOVA using type of organisational change (5 levels) and job level (7 levels) within the organisation as the factors (in SPSS). I followed Andy Field's procedure (<em>Discovering Statistics Using SPSS</em>, third edition) and I cannot manage to get the option of Post-Hoc tests for ca... | 74,353 |
<p>So I have a multi-label classification problem where the exact number of labels in each test set example is unknown. The loss function is mean F1-score which is </p>
<p><img src="http://i.stack.imgur.com/5bMSS.png" alt="enter image description here"></p>
<p>where p is the precision and r is the recall. I also ha... | 74,354 |
<p>I have a time-series forecasting task and would like some input on variable selection and regularisation.</p>
<p>My problem has the following characteristics:</p>
<ul>
<li>2,000,000 sample size.</li>
<li>Most of the time, no change in the response. Change in the response happens 0.3% of the time and is what I'm in... | 74,355 |
<p>I work in a problem where:</p>
<ul>
<li>The input data is a collection of time series from different sensor
modalities, where each sensor comes with different acquisition rates
and dynamic ranges</li>
<li>The number of potential features vastly exceeds the number of
instances (i.e. $p \gg N$)</li>
</ul>
<p>My ques... | 74,356 |
<p>Suppose a data set contains the numbers $1-100$ (i.e. $\{1, \dots, 100 \}$). In $10$-fold cross validation, the data set is divided into $10$ subsets with one used as the validation data set. For example, one such division is $S_1 = \{1, \dots, 10 \}$, $S_2 = \{11, \dots, 20 \}, \dots, S_{10} = \{91, \dots, 100 \}$.... | 74,357 |
<p>I computed the T-score and P-value using <code>t.test()</code> for my data, and finally I've plotted the density of my p-value and I've got strange plot. I don't know, why I see peak around 0, which it's density is bigger than 1 ?
can anybody help me with the interpretation of this plot ? I used the <code>plot(dens... | 49,345 |
<p>I would like to specify a multivariate model with <code>lme</code> with a random effect for group which is independent across variables. I found <a href="http://scs.math.yorku.ca/index.php/Mixed_Models_with_R/Multivariate_Mixed_Models.Rmd" rel="nofollow">this post</a>,
which explains that the model specified as:</p>... | 74,358 |
<p>Through the last year I have been working with support vector machines for a binary text classification task. Having used software such as R and Rapidminer I have not spent much time on understanding what actually goes on inside support vector machines. This I have now started looking into in the hope of getting a b... | 74,359 |
<p>I have a set of results of independent measurements of some physical quantity. As an example I give here real expermental data on methanol refractive index at 25 degrees Celsius published in scientific literature from 1960 to 2011:</p>
<pre><code>data={{1960, 1.32652}, {1961, 1.32662}, {1963, 1.32650}, {1963,
1.... | 74,360 |
<p>I have problem with real basics. I have variable that has p=.000 in Shapiro-Wilk. As I looked on the histogram it appears that the cause is natural limit for this measurement (value 0, skewness > 1,5).I'm wondering what whould be the best way to present this data as descriptives.
What parameters of descriptive &... | 74,361 |
<p>I use <a href="http://stat.ethz.ch/R-manual/R-devel/library/stats/html/optim.html" rel="nofollow">optim()</a> in R to do a lot of MLE. I've used the approach for a lot of problems, but the one I'm working on right now consists of fitting the parameters of the generalized extreme value distribution (GEV). There are ... | 47,570 |
<p>Is there anything wrong with regressing a ratio on itself? For example can we regress the log(savings ratio) on log(income) or the log(debt to income) ratio on log(income)? If not, should we use the log transformation to take income to the RHS and regress log(savings) on log(income)? If using a log transformation is... | 74,362 |
<p>I am trying to calculate the average of hourly data of three sensors but the hourly timestamps of all three sensors are different. How is it possible to measure the average of hourly data of all three sensors at a regular interval of hours say- 01:00,02:00,03:00 and so on.</p>
<p>And also is it possible to start an... | 74,363 |
<p>I've the following situation.</p>
<p>I've a binary classifier which classifies input feature vectors into either of two classes 'y' or 'n', along with the probability of it being in either of the classes P_y and P_n. I know that the classifier is right 60% of the time. How do I estimate the true probability of it b... | 37,217 |
<p>I have a GLMM of the form: </p>
<pre><code>lmer(present? ~ factor1 + factor2 + continuous + factor1*continuous +
(1 | factor3), family=binomial)
</code></pre>
<p>When I use <code>drop1(model, test="Chi")</code>, I get different results than if I use <code>Anova(model, type="III")</code> from the c... | 47,657 |
<p>I need to get as accurate as possible a value for the brightness of a mainly stable light source given twelve sample luminosity values. The sensor is imperfect, and the light can occasionally "flicker" brighter or darker, which can be ignored, hence my need for outlier detection (I think?).</p>
<p>I've done some re... | 74,364 |
<p>I am implementing the ARIMAX model for stock price predictions. To select the order, I looped through $0\le p,d,q\le10$ and found the best order to be (1,0,10). I'm a bit confused how to interpret these results. How do I tell if its reasonable, and what does this imply about the data?</p> | 37,220 |
<p>I know 3 methods to do parameter estimation, ML, MAP and Bayes approach. And for MAP and Bayes approach, we need to pick priors for parameters, right? </p>
<p>Say I have this model $p(x|\alpha,\beta)$, in which $\alpha,\beta$ are parameters, in order to do the estimation using MAP or Bayes, I read in the book that ... | 37,221 |
<p>I have a dependent variable (in counts, i.e., a number of technicians). My independent variable is a grouping factor (control and treatment). From the literature, the average number of technician required for the procedure is 3 with SD of 1. I would like to calculate a sample size to determine significant changes of... | 74,365 |
<p>An experiment has two possible outcomes: A or B. In 20 experiments, A happened 2 times, and B happens 18 times. What would I expect from a larger number of experiments? With what confidence can I say that the mean number of outcome A is 10%?</p> | 74,366 |
<p>I have to incorporate a number of line plots in a Latex document and I want to get a very high quality.</p>
<p>Are there any website that show some templates or default plots styles that I can use. Myself I am not good in designing this kind of plot style, so I am searching some good basic settings for the tool I w... | 74,367 |
<p>Let's say we created a plot, with labels:</p>
<pre><code>plot(1, xlab = "text", ylab = "text times three") # text too small
</code></pre>
<p>In this plot there is still a lot of free region to enlarge the text. We could do so by using cex.lab, like this:</p>
<pre><code>par(cex.lab = 2)
plot(1, xlab = "text", yla... | 49,011 |
<p>Despite this being of a program-related question I was asked to submit this here instead stackoverflow.</p>
<p>Is it possible to have confint use the robust variance-covariance matrix obtained by vcovHC (from the sandwich package) after fitting a model? I\ve been looking around without finding it..</p> | 49,012 |
<p>consider the following sorted sample: </p>
<p>$x_1<x_2<\ldots<x_n$</p>
<p>and the kernel function:</p>
<p>$h(j)=\log(x_j-x_1), j>1$. </p>
<p>Now, it turns out that when I draw data
from many continuous distributions, sort
them and compute $h(j)$, the plot of the
$h(j)$ as a function of $j$ is conc... | 37,231 |
<p>My background is in labor economics/applied micro but I am currently working with data collected from a field experiment. My experimental/micro skills are rusty to say the least.</p>
<p>In my data, I observe individuals choosing one of the choices $A, B, C, D$. The value of the choice is realized after the choice. ... | 74,368 |
<p>I have a set of Likert type items asking respondents their attitude on different topics. For example, attitudes toward drugs/alcohol where 1=strongl disagree and 5=strongly agree to the statement "I think it is okay for someone my age to smoke marijuana." The 6 items in this particular scale are then scored using th... | 36,204 |
<p>Near the middle of page 16 of Andrew Ng's <a href="http://cs229.stanford.edu/notes/cs229-notes3.pdf" rel="nofollow">notes on SVM</a>, he explained an intuitive view of kernel as measuring similarity between observations, but then added the caveat that</p>
<blockquote>
<p>there are things wrong with this intuition... | 74,369 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/26650/how-do-i-reference-a-regression-models-coefficients-standard-errors">How do I reference a regression model's coefficient's standard errors?</a> </p>
</blockquote>
<p>If I have a dataset:</p>
... | 49,930 |
<p>A massive problem in communicating the results of statistical calculations to the media and to the public is how we communicate uncertainty. Certainly most mass media seems to like a hard and fast number, even though except in a relatively small number of cases, numbers always have some uncertainty.</p>
<p>So, how ... | 74,370 |
<p>I want to estimate</p>
<p>$\log Y_t=\beta_0+\beta_1\log X_{1t}+\beta_2\log X_{2t}+e_t$</p>
<p>Using ADF-tests, I have found that both $\{\log Y_t\}$ and $\{\log X_{1t}\}$ are I(1) (i.e. they contain a unit root), while $\{\log X_{2t}\}$ is I(2). I have checked that $\{\Delta \log Y_t\}$, $\{\Delta \log X_{1t}\}$ a... | 37,238 |
<p>Consider a kind of auction where you are presented with, say, 1000 prospective clients. Based on information about these prospectives--age, sex, race, income, educational achievement and the like--you may 'bid' to pitch your product to some fraction of them, say 250. (Ignore the cost of bidding.) To maximize your ch... | 31,335 |
<p>I'm trying to fashion survey experiments for which the demographic composition of the samples needs to be as close as possible to a 'golden' composition. For concreteness, let's say the 'golden' composition is <code>14% middle class, 35% upper-middle class, and 51% upper class</code>.</p>
<p>I have a whole bunch of... | 74,371 |
<p>I would like to compare the effect of one IV ("sensation seeking") on a DV ("intended infidelity") based on another IV ("gender"). Actually I really just want to compare the means. So I would like to compare the mean effect of sensation seeking (a continuous variable with 5 levels) for males and females on intended ... | 74,372 |
<p>I am drafting a literature review on a current public health issue where data are confounded: </p>
<p><strong>What are common historical case-studies that are used in public health/epidemiology education where invalid or confounded relationships or inferences were intentionally or erroneously employed in public hea... | 74,373 |
<p>I am estimating a linear probability model with a hierarchical structure. I am bootstrapping standard errors to test the significance of the coefficients in order to double check the parametric estimates of the standard errors. </p>
<p>In the bootstrapping process I am finding that the coefficients are all positiv... | 37,240 |
<p>I have a set of data for companies in a certain industry. The data set spans two consecutive years, 2000 and 2001. </p>
<p>Let's say I have 100 unique companies in the dataset and I calculate average service time for each company and for each year. </p>
<p>How do I test whether the average waiting time for company... | 74,374 |
<p>I currently have a gradient boosting model that uses the <code>gbm</code> package in R that classifies observations at the end of a year. Daily behaviors are logged for each observation (with most of them zero). The model is built on observations which have a year's worth of complete data and performs well out of sa... | 74,375 |
<ol>
<li><p>What is the difference between quasi-likelihood estimating equations, and GEE?</p>
<p>From <a href="http://www.biostat.umn.edu/~xianghua/8452/note/05GEE.pdf" rel="nofollow">a note</a></p>
<blockquote>
<p>Quasi-score function is for independent, over-dispersed data (Poisson or binomial), while GEE1 is fo... | 1,035 |
<p>The method that I'm familiar with for constructing a random forest is as follows:
(from <a href="http://www.stat.berkeley.edu/~breiman/RandomForests/cc_home.htm" rel="nofollow">http://www.stat.berkeley.edu/~breiman/RandomForests/cc_home.htm</a>)</p>
<p>To build a tree in the forest we:</p>
<ol>
<li>
Bootstrap a sa... | 74,376 |
<p>Suppose I have repeated observations on individuals, which I've analyzed using a generalized estimating equation (GEE). What is the procedure for computing the prediction interval for future observations given values of the predictors? I would appreciate either instructions or references. Thank you.</p> | 74,377 |
<p>When should I use weights when performing a logistic regression? The weights I'm referring to are sampling weights from a survey? Or should I just use the unweighted data?</p> | 74,378 |
<p>It is clear to me, and well explained on multiple sites, what information the values on the diagonal of the hat matrix give for linear regression.</p>
<p>The hat matrix of a logistic regression model is less clear to me. Is it identical to the information you get out of the hat matrix applying linear regression? Th... | 74,379 |
<p>I'm trying to model a real-world random variable that behaves approximately as a Gaussian, so a Normal distribution fit is reasonable but far from perfect.</p>
<p>However, I only care about its tail, that is, I only care about finding $x$ such as $P(X > x) < p$, with $p$ anywhere between 1% and 5%. I'm model... | 74,380 |
<p>Is the power of a logistic regression and a t-test equivalent? If so, they should be "data density equivalent" by which I mean that the same number of underlying observations yields the same power given a fixed alpha of .05. Consider two cases:</p>
<ol>
<li>[The parametric t-test]: 30 draws from a binomial observ... | 74,381 |
<p>Basically, I want to manually compute what <code>predict(princomp(somedata))</code> produces.</p>
<p>In order to do that I need to have coefficients matrix so that</p>
<pre><code>newdata %*% coefficients
</code></pre>
<p>would produce the predicted values of each component.</p>
<p>Can anybody give me a clue to g... | 74,382 |
<p>As you know, there are many password generators out there to increase computer security.</p>
<p>Suppose I am given such a password (say, a string of letters, numbers, symbols, etc.), is there a way for me to test how random it is? Is there some sort of index for this measurement?</p>
<p>Thanks!</p> | 37,247 |
<p>I know PCA and PLS are considered as alternative method to each other. But I am thinking about a kind of combination of the two in case of lots of predictors with little variability.</p>
<p>In that case, when I run 1-component PLS with original predictors, it does not produce a meaningful model in terms of predicti... | 74,383 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/25211/simple-combination-probability-question-based-on-string-length-and-possible-char">Simple combination/probability question based on string-length and possible-characters</a> </p>
</blockquote>
<p>Supp... | 49,931 |
<p>The alpha-expansion algorithm described <a href="http://books.google.co.in/books?id=7dzpHCHzNQ4C&pg=PA592&lpg=PA592&dq=alpha+expansion+algorithm&source=bl&ots=pu1CCm--AR&sig=PIN3b33Wm02_FWi3f1dJO_np0W8&hl=en&sa=X&ei=Z2d8T4veCsrnrAetw6THAg&redir_esc=y#v=onepage&q=alpha%20ex... | 74,384 |
<p>It's well known that members of the public have difficulty comprehending numbers over a certain size. A common tricky issue for people communicating demographic trends is helping people make sense of rates out of 100,000. This is an important issue in helping people make sense of changing health and crime statistics... | 74,385 |
<p>Let's say I have a $m \times n$ matrix where $m$ is the number of points and $n$ is the number of dimensions. I would like to give a target dimension parameter which is let's say d. d can be a set of values like $\{2,4,6,\ldots,n\}$. I would then approach the problem using Fisher's linear discriminant analysis to gi... | 74,386 |
<p>From <em>Robert (The Bayesian Choice, 2001)</em>, it is proposed that the Bayes Estimator associated with the prior distribution $\pi$ and the multilinear loss is a $(k_2/(k_1+k_2))$ fractile of $\pi(\theta|x)$.</p>
<p>The proof follows that</p>
<p>$$
E^\pi[L_{k_1,k_2}(\theta,d|x)] = k_1\int\limits_{-\infty}^{d} (... | 49,050 |
<p>Since OLS tries to measure E[Y|X], and regression trees try to partition the data into different branches, then take means of the response under different branches, is it reasonable to say that regression trees strictly dominate OLS in prediction? Also, since OLS is not robust to outliers, would it be reasonable to... | 1,036 |
<p>I use Andrew F. Hayes' macro for SPSS (HCREG at <a href="http://www.afhayes.com/spss-sas-and-mplus-macros-and-code.html" rel="nofollow">http://www.afhayes.com/spss-sas-and-mplus-macros-and-code.html</a>) to perform multiple regression analyses with robust standard errors.</p>
<p>The information I get in the output ... | 1,037 |
<p>I have seen many places where they have input/output datasets where they first create a linear regression line, correct the bias, and then only use that data for their model. I didn't get what this bias correction is?</p> | 74,387 |
<p>A person is trying to claim that psychics exist by flipping a coin 10 times for each person behind a screen. n=10 p=1/2
Its created into a one tailed test with significance level at .001. The first 999 people do not get enough right to reject the null hypothesis. But the 1000th person gets all 10 right.
if Y is the... | 74,388 |
<p>These are the values:</p>
<pre><code>18.2 17.6
------------------------------------------------------------------------------------------------------------
18.9 18.6
------------------------------------------------... | 49,053 |
<p>I have three site temperature types: cold, medium, and hot. This is a fixed effect - I am specifically am testing if temperature affects my response variable. I believe temperature type is my 'block'. </p>
<p>I will have three sites for each temperature type. I think site is a random effect. Within each site, I wil... | 74,389 |
<p>I don't know what such plots are called and thus I just gave this question a stupid title.</p>
<p>Let's say I have an ordered dataset as follows</p>
<pre><code>4253 4262 4270 4383 4394 4476 4635 ...
</code></pre>
<p>Each number corresponds to the amount of postings a certain user contributed to a website. ... | 74,390 |
<p>If I'm watching a series of accounts for transactions going in and transactions going out, I want to notice unusually large or transactions for any particular account on any particular day.</p>
<p>So if account A typically moves a few hundred dollars and one day moves five thousand dollars, that's a clear outlier.
... | 37,254 |
<p>I am trying to work out Example 2 from Casella and George's paper "Explaining the Gibbs Sampler" in R.</p>
<p>The example is:</p>
<pre><code>f(x | y) = y*exp(-yx)
f(y | x) = x*exp(-xy)
where x, y are defined on [0,B]
</code></pre>
<p>The idea is to generate the distribution of f(x).</p>
<p>My code (below) works... | 74,391 |
<p>I have time series, for example, gdp and unemployment(<code>unemp</code>), freq= 4. </p>
<p>What if I interpret it as cross-sectional data and do cross-sectional analysis instead of time series? </p>
<p>My task is to test how unemployment affects gdp. </p>
<p>Is it allowed to do that kind of analysis? </p>
<p>Do... | 74,392 |
<p>I have a spectrum. Specifically, my data is relative intensity $[I_{\tilde{\nu}}]$ versus wavenumbers $[\tilde{\nu}]$. The wavenumbers are equally sampled so that ${d\tilde{\nu}} = c$, where $c$ is some constant.</p>
<p>However, I need the data to be given in terms of wavelength $\lambda = \frac{1}{\tilde{\nu}}$.
W... | 74,393 |
<p>I am trying to find out if I can somehow assess if one model fits my data significantly better than another model? They are both ordinal regressions and we have introduced an additional interaction term in the second model. Now we want to know if the model has improved. Do I only look at the model fit indices? How d... | 37,261 |
<p>So I've been reading various online tutorials and I've not come across and example which is similar to what I'm trying to do. I've thought up this example because I was struggling to explain with words alone. It's really basic but hopefully illustrates the concept:</p>
<pre><code>movie_eg=data.frame(score_children=... | 74,394 |
<p>I have read several textbook descriptions on RVM and none of them provide an adequate (plain English) explanation of how RVM achieves sparsity.</p>
<p>I am left feeling like the authors left out a paragraph of text that would have connected the dots and instead decided to replace (rather than supplement) it with ma... | 37,263 |
<p>I have run an online poll on two candidates. Participants are shown both candidates and are asked to determine which one they like better. Here are the labels on my Likert scale:</p>
<ul>
<li>Strongly for Romney</li>
<li>Leaning towards Romney</li>
<li>Neutral</li>
<li>Leaning towards Obama</li>
<li>Strongly for Ob... | 74,395 |
<p>I have a dependent variable that includes four categories. I also have four continuous independent variables. The 3rd category covers the largest group in the sample. Is it important to choose the category covering largest group as a reference factor or can I choose another one that would make sense for comparisons?... | 37,264 |
<p>I am using proc mixed for multilevel hierarchical data. What should be the acceptable range for Standard Error values for Fixed Effects?</p> | 74,396 |
<p>I have a question regarding the best practice for dealing with cross-loadings on factors after conducting an exploratory factor analysis using a promax rotation. Just to give a bit of background information, I am trying to determine the factor structure of a set of 20 questions that I created about spirituality (bas... | 47,975 |
<p>I am looking to do a linear regression on two independent variables that will be present in varying proportions.</p>
<p>For example trying to do a linear regression on $Y$ which is payment behavior (payback rate) of customers based on the the quality (let's say Gini coefficient) of the new and existing customer cre... | 37,266 |
<p>I am trying to implement the ID3 algorithm on a data set. However, all attributes are continuous and can have values between 1-10. I found that we have to specify the bin intervals for discretization but couldn't understand how to do this exactly. </p>
<p>Can some one explain on how to do this? The <a href="http://... | 74,397 |
<p>What are some typical approaches to handling incomplete data in the Kalman Filter? I'm talking about the situation where some elements of the observed vector $y_t$ are missing, distinct from the case where an entire observed vector $y_t$ is missed. Another way of thinking about this would be that the dimension $p$ o... | 4,246 |
<p>I want to evaluate a Gaussian PDF that does not exist because the determinant of sigma is either approx 0 or -inf (depends on parameters), and the condition number is of order 10^20.</p>
<p>I need this density because I want to find the posterior mixing coefficients in an inverse problem with a Gaussian mixture pri... | 74,398 |
<p>I want to estimate the survival function $S(t_0)=1-F(t_0)$, at a specific point $t_0$ where $F$ is a continuous cumulative distribution function, based on an uncensored sample $x_1,..,x_n$ and a nonparametric estimator. So far, I am considering two estimators $\hat S(t_0)=1-\hat F(t_0)$, where $\hat F$ is</p>
<p>(1... | 37,268 |
<p>I am having the following problem. I have a group of words which are all permutations of each other. On a random dataset of DNA sequences I can calculate the distribution of the number of word occurrences. On my biological dataset I would like to compare the word occurrences with the distribution of those on random ... | 37,269 |
<p>I've successfully implemented a RBM and trained it with CD-k, but I now have some issues doing the same with Convolutional RBM. </p>
<p>The visible and hidden biases gradients are easy to compute: v1 - v2 for visible bias and h1_k - h2_k for the hidden bias. But I failed to see how to compute the gradients for the ... | 74,399 |
<p>I have a series of descriptors, some continuous, some discrete and an output variable which is dichotomous.</p>
<p>I have several parameters, but for the sake of simplicity let's say my data look like:</p>
<pre><code> Sex | Age | Genotype | Dose 1 | Dose 2 | Outcome
------|-------|------------|---------|... | 49,250 |
<p>I have dependent variable matrix $Y_{i,j}$ and feature matrix $X_{i,k}$. My objective is to predict each element of the vector $[y_{i,0},...,y_{i,J}]$ by using new observations of the features, $[x_{i,0},...,x_{i,K}]$, i.e. to estimate $Y_{i,j} = f(X_{i,k})$.</p>
<p>In my problem, all the dependent variables are cl... | 37,270 |
<p>I don't really know what's possible, and would like a pointer in the right direction. Many thanks.</p>
<p>I have measurements of time and position which could be anything from a person walking, a vehicle on a road, or in a car park, or a printer in an office. I need to work out journey times for vehicles between tw... | 49,251 |
<p>I injected three different cRNAs constructs (construct A,B and C) into oocytes and the oocytes expressed the respective cRNAs as respective ion channels (ion channel A,B and C). My aim was to test whether these ion channels function similarly or not. Then, I measured the concentration-response relationships to deter... | 74,400 |
<p>I'm stuck with this problem on quality control and p-charts. </p>
<p>There is a given process, monitored periodically taking samples of 100 items each and counting the number that are defective. In the last 50 samples we found a total of 622 defective items.</p>
<p>I'm OK for the 3-sigma limits of the p-chart and ... | 74,401 |
<p><strong>Brief intro:</strong> I'm not really sure how to appropriately treat the dependent variables in a set of hierarchical linear models that I'm trying to run. In my models, Level 1 units are children and Level 2 units are schools (we don't have classroom info so there is no nesting level for this).</p>
<p><str... | 74,402 |
<p>I have a posterior distribution over a set of parameters denoted by $\theta = \{w, \phi, \lambda\}$ and the posterior is the joint distribution given the observed data i.e. $P(\theta | D)$. Now, this posterior is a multivariate normal distribution (due to the approximate way it is estimated).</p>
<p>Now I want to f... | 74,403 |
<p>I try to fit a model of the following form
$$
Y = (\beta X - Z)^+ + \epsilon,
$$
where $Y,Z \ge 0$ and $X,Y,Z \in \mathbb{R}$ and $(x)^+ = \max(x,0)$.
Note that $Y,X$ and $Z$ come from a sample, especially $Z$ is not a constant.
I did this in R in the following way:
<pre><code>
positivePart<- function(x){
x[x... | 49,070 |
<p><em><strong>Task:</strong></em><br>
I have e.g. 1 control group and 7 experimental groups which are treated differently. All groups have a dependent <strong>binomial</strong> variable: 1 = success, 0 = no success. </p>
<p>I want to conduct <strong>sequential tests</strong>, which version is "performing" better, be... | 49,072 |
<p>I have a short question regarding interaction variables:</p>
<ol>
<li><p>In a logit regression with 2 independent dichotomous variables (A and B), both variables are significant. By including the interaction (AxB) in the regression, B becomes insignificant.
Is the high (0.6) and significant correlation between (AxB... | 74,404 |
<p>I am performing some regression task, where I try to discover the underlying multivariate Gaussians from a set of $n$, $p$-dimensional vectors. For example, given a split of the set into $S_i$ and $S_j$ I will calculate the sample means and covariance matrices (${\sum}_{i,j}$)and decide which is the best split based... | 49,075 |
<p>I have run an ACF on a function in R and it returns:</p>
<pre><code>Autocorrelations of series ‘sine.curve’, by lag
</code></pre>
<blockquote>
<pre><code> 0 1 2 3 4 5 6 7 8 9 10 11
1.000 0.257 -0.712 -0.677 0.249 0.825 0.243 -0.632 -0.633 0.242 0.731... | 37,629 |
<pre><code>import sympy
sympy.init_printing()
x, y, mu, sigma, density1, density2 = sympy.symbols('x y mu sigma density1 density2')
eq1 = sympy.Eq(density1, 1/(sympy.sqrt(2*sympy.pi)*sigma)
*sympy.exp(-(x-mu)**2/(2*sigma**2))) # normal
eq2 = sympy.Eq(y, sympy.exp(x)) ... | 74,405 |
<p>So I often have the situation where I want to compare the runtime of two computer processes. Even when measuring only user+system time (as opposed to wall clock time) there is a random element in the measured time. I'm going to suppose that this randomness is poisson distributed (task switches and interrupts from ra... | 37,275 |
<p>In some real-life problems such as authentication, we only have training data for one label (x is authenticated) while the other label doesn't have any data or only few entries (x is an imposter).</p>
<p>What kind of changes should we do in order to adjust a classifier to deal with a label targeted for other/unknow... | 74,406 |
<p>I have a two stage model where coefficients of model 1 become the $y$-vector for model 2. I have standard errors for those coefficients, and I want to weigh the observations in model 2 according to the standard error that the corresponding coefficient had in model 1. I believe the correct way to do this is weigh the... | 74,407 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.