question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I get very poor replication of longitudinal parameters from my own program using the Box-Jenkins model. I had no such problem with my own program generating AR(1) Gaussian data. Is there some trick that I haven't discovered yet? I would like to use the validation framework of Martinez-Rivera & Ventosa-Santaul... | 68,993 |
<p>I have a simple question. Suppose $X=(X_1,X_2,X_3)$ is multivariate normal. What's the best (quickest) way to draw from the conditional density $X_1\mid \exp(X_1)+\exp(X_2)+X_3$?</p> | 68,994 |
<p>Based on this post, <a href="http://quant.stackexchange.com/questions/111/how-can-i-go-about-applying-machine-learning-algorithms-to-stock-markets">http://quant.stackexchange.com/questions/111/how-can-i-go-about-applying-machine-learning-algorithms-to-stock-markets</a>, I want to digest Elements of Statistical Learn... | 39,318 |
<p>Does, in some sense, Kernel Ridge Regression refer to the same class of problems as Support Vector Regression? Should I use them almost equivalently?</p> | 68,995 |
<p>What is the rationale, if any, to use Discriminant Analysis (DA) on the results of a clustering algorithm like k-means, as I see it from time to time in the literature (essentially on clinical subtyping of mental disorders)?</p>
<p>It is generally not recommended to test for group differences on the variables that ... | 39,320 |
<p>Here are four graphs, </p>
<p>1, autocorrelation, autocovariance, partial-correlation and cross-correlation calculated from a time series are given.</p>
<p>2, The time series</p>
<p>I need to do some predictions on them.</p>
<p>My questions are 4 :</p>
<p>1, I do not quite understand what these four graphs can ... | 39,321 |
<p>I am conducting some statistical tests on a rare event (11 cases out of 171 patient sample). I have two main hypotheses, but in the mean time I also want to conduct some exploratory tests on 6 other variables, in order to explore possible associations. </p>
<p>(1) I am wondering if there are any rules about the num... | 38,995 |
<p>I was looking at the following question from "One Thousand Exercises in Probability" by Grimmett, page 25, question 16 (not homework just self-study):</p>
<blockquote>
<p>Let $X$ and $Y$ be independent Bernoulli random variables with $p = 1/2$.
Show that $X + Y$ and $|X − Y|$ are dependent though uncorrelated.<... | 49,317 |
<p>I have a question concerning about one step in the Metropolis algorithm. The algorithm <a href="http://en.wikipedia.org/wiki/Metropolis-Hastings_algorithm" rel="nofollow">proceeds as following</a>,</p>
<ol>
<li>Generate a proposed new sample value from the jumping distribution $Q(x'|x_t)$</li>
<li>Calculate the ac... | 68,996 |
<p>Suppose we are given a matrix of many rows (different genes for example) and few columns (different time points) and we want to identify the top rows (genes) that are following a trend, like monotonically increasing or decreasing. What is a good method to perform this in R?</p>
<p>The answers providing also a stati... | 39,329 |
<p>For example assume I have three observations as given in matrix A</p>
<p>$A = \left[ \begin{array}{ccc}
1 & 0 & 1 \\
1 & 1 & 0 \\
0 & 1 & 1 \\
\end{array} \right]$</p>
<p>each row vector of matrix A has a weight value associated with it as $w = (0.5, 0.3, 0.2) $</p>
<p>Using the equation i... | 68,997 |
<p>In an experiment, I'm counting failures on an semiconductor device for a given fluence (i.e. amount) of neutron radiation. The failures occur according to a Poisson law.</p>
<p>The fluence is provided by the neutron facility. The fluence standard error $\Delta{x} = \frac{\text{s}}{\sqrt{n}}$ has been computed by th... | 68,998 |
<p>I want to design a Bayesian model for a simple asset allocation problem.</p>
<p>Say I can buy $a_i$ amounts of $N$ assets. The return values of these assets are given by random variables $r_i$ with known posteriors $p(r_i | \textbf{x})$, given some known data about the market $\textbf{x}$.</p>
<p>I define my util... | 68,999 |
<p>For some practical application I recently came about the following thought experiment. Can anybody help?</p>
<p>Suppose we administer a survey A to measure a variable $Y$. The response probabilities may depend on $Y$, as in $$P(R_a=1|Y)$$ where $R_a$ is the response indicator, 0 for nonresponse, 1 for response. We ... | 29,253 |
<p>Trying to figure out a way to balance small samples. Comparing ratios received from a survey, but sometimes I will have 25 survey responses and sometimes I will have 1. The ratios I look at might be the same but I think I need to take into consideration that one ratio is based on 25 surveys and the other is based ... | 69,000 |
<p>For 50 patients, 2 measurements were done: 1 on a phantom, 1 on a reference point. Ideally, the difference between the measurements would be zero. I want to test whether the difference is significant. </p>
<p>Can anybody help me with this problem? Statistics isn't my strongest side. I hope I stated the situation we... | 69,001 |
<p>Is the high leverage sample observation considered a subset of the population, forcing its squared residual to be less than or equal to the population variance? Or am I misinterpreting the question? I'm trying to determine why the answer is false to the below question.</p>
<p><img src="http://i.stack.imgur.com/XtsV... | 69,002 |
<p>Many of the people define graphical models with factors, each with 'conditional probability tables' (CPT) and perform inference on them. </p>
<p>But more realistic case is when you can't define full probability tables, and instead you define functions of features with some probabilities (as in discriminative models... | 69,003 |
<p>I have two different regression models which I learned from two different data sets.</p>
<p>Is there any statistical method which shows the significance of models based on the number of parameters and cross validation errors?</p>
<p>The problem is that I used two different data sets and I worry that it might not m... | 29,256 |
<p>So I've been working on a problem in my probability class on which I have become stuck. It involves <code>X1 X2 ... Xn ~ Poisson(lambda)</code> </p>
<p>1 - We were instructed to show that <code>X_bar</code> was sufficient.</p>
<p>Sol'n: I did this using factorization, and by finding <code>T(x) = Sum(x_i)/n</code>,... | 69,004 |
<p>I have just completed a simple exercise with 2 variables (X and Y) to understand how K-Means clustering works. The results look like this,</p>
<p><img src="http://i.stack.imgur.com/QAl9d.png" alt="Simple K-Means Clustering Result"></p>
<p>My questions is, if I have another column Z, how should the scatter plot be ... | 69,005 |
<p>As you probably know, the CDFs for many widely-used distributions are difficult, if not impossible, to express in closed form without the use of special functions </p>
<ul>
<li><p>The normal distribution uses $\mathrm{erf}$.</p></li>
<li><p>Student's $t$-distribution requires the incomplete beta function or the Eul... | 38,474 |
<p><strong>Background:</strong><p>
I'm working on a statistics project that includes data for people who post a certain project online they need another to complete. Many people will apply to work on the project, but the poster will only choose one to complete it. There is a "back and forth" between the two parties un... | 69,006 |
<p>What would you guys suggest as a good introduction book to small area estimation?</p> | 69,007 |
<p>I estimate a saturated / just-identified model (specifically: an APIM model, actor-partner-interdepence model) with the R package <code>lavaan</code>.</p>
<p>This model is saturated and should have 0 $df$. This is true for the "GLS" generalized least squares estimator. With "ML" maximum likelihood estimation, howev... | 69,008 |
<p>I am interested in determining the optimal number of clusters calculated by the PAM clustering algorithm using the Calinski-Harabasz (CH) index. To that end, I found 2 different R functions calculating CH values for a given clustering, but which returned different results: <a href="http://rss.acs.unt.edu/Rdoc/librar... | 69,009 |
<p>I am running a frequency count on the instances of powerless of language in the language of prosecuting attorneys and the same frequency count of the defendants language. </p>
<p>I am asking if the frequency of the powerless language by women makes a favorable verdict and less powerless language by men creates a fa... | 69,010 |
<p>I've been wanting to experiment with a neural network for a classification problem that I'm facing. I ran into papers that talk of RBMs. But from what I can understand, they are no different from having a multilayer neural network. Is this accurate?</p>
<p>Moreover I work with R and am not seeing any canned package... | 69,011 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/38290/why-does-standard-error-not-involve-population-size">Why does standard error not involve population size?</a> </p>
</blockquote>
<p>When calculating confidence intervals for population parameters, th... | 49,818 |
<p>I am trying to model annual tree nut production using climate predictors. </p>
<p>The nut data (dependent) is a binary timeseries (0,1 - representing unsuccessful and successful nut production), with one observation per year, and with 90 years of data and two missing years (88 onservations). </p>
<p>The independe... | 69,012 |
<p>I'm studying time series prediction and I have some questions.</p>
<p>Is the Moving Averages movel studied the methods of the ARMA family has the same concept as the methods studied in Moving Averages technical analysis stock trading?</p>
<p>Is there any place where I can find implementations in <code>.Net</code> ... | 69,013 |
<p>I have data for 1000 students' performance over 10 different tests on a scale of 0 -100 (a 1000 rows X 10 col matrix).
I calculated the mean score and the associated coefficient of variation for each student.
Now I wish to sort / rank students who consistently perform better, that is, have a high mean score and low ... | 69,014 |
<p>How do you report Kruskal Wallis One Way Anova and post hoc results according to <a href="http://www.apastyle.org/" rel="nofollow">APA</a> (American Psychological Association) 6th ed. standards? I have tried to find a template for reporting the results for the Kruskal-Wallis one way analysis of variance test and pos... | 40,249 |
<p>I am new to R and seeking some advice. I have a set (~20M) of data describing on which step a process did fail or succeeded:</p>
<pre><code>name;star_time;step1;step2;step3
A;2011-07-22 11:02:44;passed;passed;failed
B;2011-03-06 19:33:06;passed;failed;failed
...
</code></pre>
<p>I want to search for clusters of pr... | 29,263 |
<p>Consider survey data from surgeries. $Y$ represents observed surgical
quality and is measured post-surgery; $X$ represents perceived surgical
difficulty level and is measured pre and post surgery.</p>
<p>It is desired to assess the relationship between $Y$ and $X_{pre}$ and also $Y$
on $X_{\delta} = X_{post} - X... | 69,015 |
<p>Is there a statistical measure for how much a variable fluctuates over time? For example a noise signal fluctuates a lot. However, if you would sort all values of the signal in time, you would have a signal that does not fluctuate at all. My first idea was to use the variance of the derivative, but I’m not sure whet... | 29,265 |
<p>Does it make any sense to apply the Dirichlet density function to only one x value and therefore one alpha parameter? (this would be the result of some bin merging)</p>
<p>I'm asking because it appears that gtool's implementation always returns 0 in such case, whereas <a href="http://stackoverflow.com/questions/10... | 24,817 |
<p>I have a small set (say, 200 data points) of estimates about the time to complete a varied group of tasks, along with the actual times used to complete those tasks. </p>
<p>These estimates are divided in four groups: 0:30, 1:00, 2:00, and 4:00. These groups indicate that the task should be completed in 30 minutes, ... | 69,016 |
<p>I have some daily data from city A, B, C.
Values from city A are highly correlated with values from other cities for lag -1,-2,-3 and -4.
I want to use Random Forest, SVM and ANN to predict values for city A. My idea is:</p>
<ol>
<li>Split data into training and testing set.</li>
<li><p>Use the formula: valueA ~ v... | 69,017 |
<p>In our group, we have measured grey matter volumes of about 20 regions of interest (ROI) and frequency of cannabis use. Now, we would like find out whether cannabis use is associated with grey matter volumes of any of the measured brain regions. Furthermore, we would like find out whether these associations differ i... | 69,018 |
<p>Suppose one wants to compute the odds ratio of a disease for a person in group $A$ versus that of a person in group $B$. Suppose we consider the following: (i) include age in the odds ratio calculation, (ii) include age and height in the odds ratio calculation. Is it possible for the odds ratio for (ii) to be much g... | 69,019 |
<p>When regressing income ($Y$) on age ($X$) moderated by gender ($Z$), I not only find significant effects for age ($X$), age squared ($X^2$), gender ($Z$), the interaction of age and gender ($XZ$), and the interaction of squared age and gender ($X^2Z$). Could anyone help me with how to interpret these results? Specif... | 29,268 |
<p>I have a set of observed Markov sequences for which I have calculated first and second order transition matrices: </p>
<p>$$M={P}(X_i=x_i|X_{i-1}=x_j)$$ and $$M^2=P(X_i=x_i|X_{i-1}=x_j,\,X_{i-2}=x_i )$$.</p>
<p>I then produced a series of Markov chains based on the transition matrix $M$ and hence recalculated the ... | 29,269 |
<p>How do I approximate the following integral using MC simulation?</p>
<p>$$
\int_{-1}^{1} \int_{-1}^{1} |x-y| \,\mathrm{d}x \,\mathrm{d}y
$$</p>
<p>Thanks!</p>
<p><strong>Edit</strong> (Some context): I am trying to learn how to use simulation to approximate integrals, and am getting some practice done when I ra... | 11,723 |
<p>I read Nonlinear Dimensionality Reduction by Lee and Verleysen [<a href="http://books.google.si/books?id=o_TIoyeO7AsC&lpg=PA8&ots=CMId9rg3Iu&dq=finite%20eight%20order%20moment%20identically%20distributed&pg=PA8#v=onepage&q=finite%20eight%20order%20moment%20identically%20distributed&f=false">G... | 69,020 |
<p>On page 192 of <a href="http://www.csiro.au/resources/pf16h" rel="nofollow">Analysing spatial point patterns in 'R' (Baddeley 2011)</a>, there are plots of the Gcross function for the amacrine dataset. I am looking for an interpretation of the plot. off/off and on/on are far below the CSR line, but on/off and off/... | 29,270 |
<p>Cross validation lets us get multiple estimates of the generalization performance of an algorithm when the performance cannot be estimated for each example independently. (As with an F1-score, we need to estimate it over all of the data.) But when we use a t-test to determine whether or not there is a difference in... | 37,993 |
<p>I want to conduct a regression analysis on a dataset of identical twins. There is a paper by <a href="http://ije.oxfordjournals.org/content/34/5/1089.full" rel="nofollow">Carlin et. al. 2005</a> which reviews the models that are designed for twin studies and includes the Stata codes in the appendix. The issue that I... | 69,021 |
<p>I'm working with text recognition and currently I'm using support vector machine method. I would like to try with neural network also. I read a few documents about how neural network works, but the theory is quite heavy and I don't know exactly how will it apply to my case. So it would be good if someone can help me... | 29,271 |
<p>I tested reactions to pictures under five conditions (neutral, high status, low status, high adhesion, low adhesion), using an EEG of 16 channels. The pictures were presented in random order for 15 times under each condition. So at best I have data from 75 trials for each subject in each channel. But as some electro... | 69,022 |
<p>I've been doing predictive modelling with R package <code>caret</code>. When resampling regression models, I get the traditional RMSE and Rsquared metrics, but also RMSE SD and Rsquared SD, for which I haven't found explanation in the manuals or documentations. Please, could anyone enlighten me?</p>
<p>Reproducible... | 69,023 |
<p>I have some experimental data that I'm trying to analyze.
I have 1 response variable and 3 explanatory variables (these are factor variables).
The explanatory variables are the presence of a disease(positive and negative),
a genetic profile (X and Y), and whether or not an MRI contrast agent was given
(YES and NO). ... | 69,024 |
<p>If a die is rolled 10 times, how do you calculate the probability that an equal number of ones and twos occur?</p>
<p>Let A be the number of ones, B the number of twos</p>
<p>I first thought it might be equal to </p>
<p>$\ (P(A=1) \times P(B=1)) + (P(A=2) \times P(B=2)) + ... + (P(A=10) \times P(B=10))$</p>
<p>... | 69,025 |
<p>I know what is a conditional probability distribution. But what is exactly <em>full conditional probability</em>?</p> | 69,026 |
<p>I am a new user of WinBUGS and have one question for your help. After running the following code, I got parameters of <code>beta0</code> through <code>beta4</code> (stats, density), but I don't know how to get the prediction of the last value of <code>h</code>, which I set to <code>NA</code> to model in the code. </... | 69,027 |
<p>I have a basic understanding of basic statistics, but I believe I've gotten myself out of my depth. </p>
<p>I have a data set with a dependent variable (time span) and three quantitative independent variables. There is also a qualitative independent variable (a type flag) but I think I can quantify it if I must. Th... | 69,028 |
<p>I have a dataset that looks like the following </p>
<pre><code>id | time | trial | success | other covariates
1 0 10 4
1 1 23 10
1 2 100 29
2 0 5 1
</code></pre>
<p>etc </p>
<p>this is basically a panel aggregated logistic regression.
Can someone point me towards a ... | 29,274 |
<p>I'm trying to model a student's semester GPA $G$ as a random variable. </p>
<p>Semester GPA is a weighted (based on credit hours) sum of a student's grade points (e.g. 0=F,1=D,2=C,3=B,4=A).</p>
<p>We can consider the students grade points in each course $G_1,...,G_n$ as random variables, each with a particular dis... | 39,385 |
<p>All,</p>
<p>Wondering if anyone has run across a package/function in R that will combine levels of a factor whose proportion of all the levels in a factor is less than some threshold? Specifically, one of the first steps in data preparation I conduct is to collapse sparse levels of factors together (say into a leve... | 69,029 |
<p>I'm trying to help a scientist design a study for the occurrence of salmonella microbes. He would like to compare an experimental antimicrobial formulation against a chlorine (bleach) at poultry farms. Because background rates of salmonella differ over time, he plans to measure % poultry w/salmonella before treatm... | 69,030 |
<p>I am currently working on some time series data, I know I can use
LOESS/ARIMA model. </p>
<p>The data is written to a vector whose length is 1000, which is a queue,
updating every 15 minutes, </p>
<p>Thus the old data will pop out while the new data push in the vector.</p>
<p>I can rerun the whole model on a sc... | 29,279 |
<p>I am implementing the Support Vector Regression (SVR) algorithm by means of quadratic programming. In order to do that, I am using an optimization library that contains a quadratic solver based on the Goldfarb Idnani active set quadratic optimization method.</p>
<p>However, the library seems not to be working the w... | 69,031 |
<p>For a continuous outcome being analyzed using GEE with a linear link, you have assurance that standard errors and point estimates are consistent with a first order trend regardless of distribution of outcome, heteroscedasticity, and mild non-linearity problems. Point estimates from the GEE are the same as those obta... | 69,032 |
<p>just wondering - is it possible to calculate Czuprow's coefficient of the convergence in R package? if so, is there some dedicated package for that purpose?</p>
<p>thanks in advance</p> | 29,282 |
<p>I'm reading a paper and the author wrote:</p>
<blockquote>
<p><strong>The effect of A,B, C on Y was studied through the use of multiple regression analysis. A,B,C were entered into the regression equation with Y as the dependent variable. The analysis of variance is presented in Table 3.
The effect of B on Y wa... | 29,283 |
<p>I'm looking for a dataset on which a diffusion kernel (also called heat kernel), used via SVM, would get better accuracy than other kernels for the classification task. I want to use such a dataset to make sure my implementation of the diffusion kernel is working, and to get a better understanding of the diffusion k... | 69,033 |
<p>So the formula for AIC is:
AIC = 2k - 2ln(L)
L is the maximized value of the likelihood function.</p>
<p>I'm modeling oxygen data in R using Non-Linear Minimization (nlm) of a maximum likelihood estimation (mle). By using the minimum command it produces the value of the estimated minimum of the function. This seem... | 69,034 |
<p>In the collapsed Gibbs sampling version of LDA, the posterior distribution of topic assignments for each word is sampled. From what I have read (e.g. <a href="http://people.cs.umass.edu/~wallach/courses/s11/cmpsci791ss/readings/griffiths02gibbs.pdf" rel="nofollow">http://people.cs.umass.edu/~wallach/courses/s11/cmp... | 29,284 |
<p>I am building a path model which links different psychological constructs. This is the replication of a model I have previously tested in another sample.</p>
<p>The model fits the data well. When however I try to add an additional variable as covariate on the DV (i.e., a variable with an arrow pointed to the DV) t... | 69,035 |
<p>I've looked over other posts regarding time series data, and am unsure if the mentioned methods would apply to what I'm trying to do, since I'm not familiar with pattern analysis methods:</p>
<p>I have time series data from two conditions. I want to identify a pattern in each condition, and then write a piece of co... | 69,036 |
<p>I want to generate two variables with (pseudo-) random numbers with an exact pearson's r. How do I do that? Python and/or R solutions would be nice!</p>
<p>I am able to generate random data that approximates a pre-specified r in python in the following way. I'm not searching for approximations but for data that wit... | 69,037 |
<p>I need a little bit guidance. I have to compare the classification performance of multiple algorithms using simple or paired t-test.</p>
<p>Let's say I have four datasets (A,B,C) with training and test samples. I am running 3 algorithms (SIFT, SURF, ORB) and compute the classification accuracy such 0.9 means 90% of... | 29,286 |
<p>I have a moving platform which moves in orthogonal axis to move a light detector to take account of positional uncertainty. I have a systematic error in space that is well described by a circular normal distribution (actually its not quite circular but the covariance matrix is almost exacty diagonal). I can think of... | 69,038 |
<p>I am using the plm library to run fixed effect regressions and the sandwich,lmtest libraries to compute robust standard errors. I have no problem running the regressions, but in some instances when I go to compute the standard errors I get the following error:</p>
<pre><code>library(plm)
library(sandwich)
library(... | 34,336 |
<p>Following <a href="http://stats.stackexchange.com/q/101407/29911">this question</a>, I am interested on the best way to display four distributions with spikes.</p>
<p>Indeed, I have four distributions with circa 75% of elements in it at the maximum value (1). I am searching for a method that is able to display grap... | 30,044 |
<p>I am hoping someone can point me in the right direction with this problem I am having.</p>
<p>I am trying to cluster geographical areas (basically using latitude and longitude as the zip code centroid) which have the highest number of deaths in a given state. But, the added constraint is that those clustered areas ... | 69,039 |
<p>I am predicting missing values by using two different methods (e.g., data imputation methods). Following I am interested to test if the predicted values, obtained by means of two different methods, are significantly different. The missing values are not normally distributed and lay in the range between 0 and 1. What... | 69,040 |
<p>I am studying the distribution of a marine species using the number of sightings as a dependent variable. When I am trying to validate the plots of the best model I am getting a non-usual pattern, and then I decided to get the null model with different distributions, and I don’t know what is causing the different le... | 69,041 |
<p>I am trying to learn about methods for learning probability estimates.
I understand how to use logistic regression for that, but I wonder if there are more complex nonlinear methods of the vein of neural networks and random forests that can give me similar results?</p>
<p>Any help would be much appreciated.</p> | 39,404 |
<p>Fitting exponential regression of form $y=ab^{x_1}c^{x_2}$
Here $x_1$ and $x_2$ are predictors and $y$ is dependent variable
how to calculate $a,b,c$ using R tool</p> | 69,042 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/1444/how-should-i-transform-non-negative-data-including-zeros">How should I transform non-negative data including zeros?</a> </p>
</blockquote>
<p>I want to perform log transformation regression in R tool ... | 49,418 |
<p>I'm looking to generate as much interesting data as I can from some 2on2 basketball games.</p>
<p>The only data I have recorded is the players on each team, and the final score.</p>
<p>What interesting things can I learn from this data? I'm interested in what I can learn about the individual players, as well as th... | 69,043 |
<p>I come across a practice where the logit (Intercept + beta* variables) is once again input as a independant variable in a single variable logistic regression against dependant variable to get intercept ($I$) and a beta ($B_0$). Finally, probability is calculated: $\frac{1}{1+e^{-(I+B_0\text{logit})}}$.</p>
<p>Why i... | 69,044 |
<p>Functions I'm familiar with include <a href="http://stat.ethz.ch/R-manual/R-patched/library/base/html/scale.html" rel="nofollow">scale</a> from base R, <a href="http://rss.acs.unt.edu/Rdoc/library/arm/html/rescale.html" rel="nofollow">rescale</a> from ARM. </p>
<p>Perhaps the best way would be to use some variant o... | 29,298 |
<p>I'm designing a toy experiment in which I'd like to model the 'attractiveness' of a credit card as a function of the interest rate it comes with:</p>
<ul>
<li>Attractiveness will be reported on a 10 point scale</li>
<li>I can vary interest rate between 0% and 25%. </li>
<li>In total, I have budget that will allow ... | 69,045 |
<p>I am curious about the consequences of changing the order of the explanatory variables in a binary logistic regression. In a recent series of logistic regressions I ran in SPSS, I found that changing the order of the explanatory variables ($z, y, x$ instead of $x, y, z$) resulted in different coefficient values and ... | 39,413 |
<p>I've a question which probably is going to show my ignorance about statistics :). I have a large set of machines that produce iron bars of certain lengths. For each machine, I have ran experiments and have a list of lengths. From those I can calculate a mean and sample standard deviation. I don't really care about t... | 69,046 |
<p>I'm looking for a method to determine the likelihood that two percentages from independent groups are EQUAL. In this case I'm looking at the likelihood of symptom improvement from patients gathered through two different methods (one traditional double-blind study and one from an online enrollment).</p>
<p>So if in ... | 39,414 |
<p>This questions might sound stupid, but... <strong>is it correct that random effects could apply only to categorical variables</strong> (like individual id, population id, ...), e.g. say $x_i$ is categorical variable:</p>
<p>$y_i$ ~ $\beta_{x_i}$</p>
<p>$\beta_{x_i}$ ~ $Norm(\mu, \delta^2)$</p>
<p>but from the pri... | 394 |
<p>Residuals are used to check a linear model's assumptions. From SAS Help 'The MIXED Procedure: Residuals and Influence Diagnostics' section we know that there are different types of residuals (<a href="http://support.sas.com/documentation/cdl/en/statug/63962/HTML/default/viewer.htm#statug_mixed_sect027.htm" rel="nofo... | 10,234 |
<p>I have a dichotomous outcome (life satisfaction). The proportion of people in my sample who are satisfied is fairly high (about 85%). I know that from my Chi-squared analysis that both income and age are significantly associated with being satisfied (both are categorical variables).</p>
<p>I want to run logistic re... | 36,047 |
<p>I am trying to use the Perl <a href="http://search.cpan.org/~iawelch/Statistics-Regression-0.53/Regression.pm" rel="nofollow">Statistics::Regression</a> package to calculate a multivariate regression.</p>
<p>The results I am getting per each of my variables are: <code>Theta</code> (the coefficient), <code>StdErr</c... | 69,047 |
<p>Given $x\sim \mathcal{N}(\mu=0, \sigma^2=1)$, the squared distances of the $x$ values to $\mu$ are distributed $\chi^2_1$.</p>
<p>I am interested in the distribution of the squared distances to an arbitrary $x$. For instance, what is the distribution of the squared distances of the observations to $x=2$? </p>
<p>I... | 69,048 |
<p>Here is a basic question that perhaps has a simple answer, but one that I was not able to find by quickly scanning the literature. </p>
<p>Suppose that I have a collection of $n$ unopened boxes. Each box $i$ contains either a red ball or a blue ball: write $c_i = 1$ if box $i$ contains a red ball, and $c_i = 0$ oth... | 39,424 |
<p>I have been researching the meaning of positive semi-definite property of correlation or covariance matrix. </p>
<p>Any information on</p>
<ul>
<li>Definition of positive semi-definiteness </li>
<li>Its Important properties, practical implications</li>
<li>The consequence of having negative determinant, impact on ... | 9,107 |
<p>Lets say I have confidence interval at 85% with 4% margin of error, and I get a value from my analysis equal to $x$.</p>
<p>Does this mean that if I were to perform the test 100 times, then at least 85 times we would expect to see a value for $x$ ranging from $.96x$ to $1.04x$?</p> | 36,051 |
<p>I have split the multi class svm to several binary classifications and obtained the individual predictions. My predicted labels are saved in a matrix 'predicted_vals' with each row containing predicted binary classification result for a particular class. What I have done is using the function</p>
<blockquote>
<p>... | 29,318 |
<p>I have a paired data consisting of $N$ = 421 samples. I would like to find out if there is statistical significance between the paired samples. Since, I do not know the underlying data distribution I select the Wilcoxon Signed Rank test for my task. I use the SciPy stats module in Python to do the job for me [0]. Th... | 49,335 |
<p>Four students sit a series of tests, each test contains 10 questions. Students are ranked 1-4 in each test depending upon who got the most questions correct.</p>
<pre><code> Tom Dick Harry Alice
Test1 Score 9 5 6 8
Test2 Score 8 3 7 4
... | 39,446 |
<p>My question is similar to this link <a href="http://stats.stackexchange.com/questions/12425/creating-a-certainty-score-from-the-votes-in-random-forests">Creating a "certainty score" from the votes in random forests?</a></p>
<p>I am trying to build a random forest for a binary response (1 & 0). Let's s... | 69,049 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.