question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I have a multiple regression model with 4 independent variable. I want to test heteroscedasticity with the Breusch-Pagan test. If I do a studentized BP test the p-value is 0,173, with a non-studentized test, it is 0,89.</p> | g65332 | [
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<p>Following one-way ANOVA, there are many possible follow-up multiple comparison tests. Holm's test (or better, the Holm-Sidak) test has lots of power, but because it works in a stepwise manner, it cannot compute confidence intervals. Its advantage over the tests than can compute confidence intervals (Tukey, Dunnett) ... | g65333 | [
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<p>What is the best blog on data visualization?</p>
<p>I'm making this question a community wiki since it is highly subjective. Please limit each answer to one link.</p> | g65334 | [
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<p>I'd like to see the answer with qualitative view on the problem, not just definition. Examples and analogous from other areas of applied math also would be good.</p>
<p>I understand, my question is silly, but I can't find good and intuitive introduction textbook on signal processing — if someone would suggest one, ... | g23863 | [
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<p>I would like to use multi-process models. in particular, I would like to apply this model: Kulu, Hill. "Migration and fertility: Competing hypotheses re-examined." European Journal of Population/Revue européenne de Démographie.</p>
<p>In the fertility equations I don't understand how the estimation procedure diffe... | g65335 | [
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<p>Let $X_{i}$, $i=0,1,\cdots$ be a sequence of random variables generated by $X_{i+1}=\rho X_{i}+W_{i}$, where $\rho$ is constant and $W_{i}$ are i.i.d random variables. Suppose $X_{0}$ is independent of $W_{i}$. Is $X_{i}$ a martingale, submartingale, or supermartingale? </p> | g23865 | [
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<p>I try to perform one-class SVM Schölkopf on LibSVM.</p>
<p>But all the predicted labels are "-1 " which is very strange.
Below is my code. I use MATLAB and libSVM. </p>
<pre>
% ex5 with iris dataset
load iris.mat ;
% choose the first class of data as target data
% and other two classes of data as negative data... | g65336 | [
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<p>I've created a multiple regression predicting 1 DV from 4 IVs (all mean-centered) + 1 interaction term between two of the IVs. The interaction term is significant.</p>
<p>I'd like to get a nifty graph comparing the effect of one of the variables included in the interaction on the DV at particular values (say, $\pm1... | g65337 | [
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<p>During fine-tuning some classifier parameters, is it correct to talk about "optimal" configuration?</p>
<p>For example, if perfect classification is impossible, but the error converges to some relatively good small value, is it correct to call it an "optimal" solution, or is it "suboptimal" because there's no singl... | g65338 | [
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<p>I was recently given the following data.</p>
<pre><code>7 1 6 6 2 8 3 7 4 6 3 3 1 8 4 5 9 3 2 4 1 4 4 3 6 3 4 2 3 2 7 2 7 4 2 4 4 4 3 2 2 4 5 8 6 4 3 1 5 5
</code></pre>
<p>I then ran a KS test as follows in R:</p>
<pre><code>ks.test(mydata,"pnorm",mean(mydata),sd(mydata))
</code></pre>
<p>and got the following:... | g23869 | [
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0.039002854377031326,
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0.066... |
<p>I want to know how to code survey data such that a similarity function can be applied on it.</p>
<p>Say I want to use cosine similarity. All the search results and QA I've found while in my search deal only with the similarity between <em>documents</em>, with vectors consisting of word frequencies or tf/idf.</p>
<... | g65339 | [
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<p>one of the reviewer of a paper of mine suggested to perform a homoscedasticity test between the results of two experiments, testing the same thing in two conditions. The experiments consisted in ratings along a 7 points likert scale.
One of the experiment results were distributed on a large range of values, while th... | g65340 | [
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<p>I understand that the outer product of two vectors, say representing two detrended time series, can represent a cross-correlation (well covariance) matrix. </p>
<p>I also know that the inverse of a correlation matrix represents the partial correlations between two variables. Geometrically, I know that the partial c... | g23870 | [
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<p>I was recently reading about Heckman selection models, and got sidetracked by how little I knew about truncated data. I was reading <a href="http://fmwww.bc.edu/EC-C/S2013/823/EC823.S2013.nn12.slides.pdf" rel="nofollow">these slides</a>, and on page 78 Baum mentions that if part of a sample has a truncated $Y$ varia... | g65341 | [
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<p>I am working with a seven item Likert Scale (1, 2......6, 7) for a classroom management. </p>
<p>How can I calculate the distance between these seven scale points? This is for instrument reliability purposes, I want to see if people find, for example, a larger difference between choice 4 and 5 and a shorter distanc... | g65342 | [
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<p>I would like to determine the relationship between two variables after controlling for a third. Specifically, I want to know if the prices of mercury and gold over time are correlated with each other more than or less than they are correlated with a generic metals price index. Is there some special signal in the rel... | g65343 | [
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<ol>
<li><p>There are 3 independent variables (carb, protein, fat) in my experiment, each with two levels (low and High). I am trying to figure out if 3-Way ANOVA would be the best method.
Example:
Carb (low and high);
Protein (low and high)
Fat (low and high)</p></li>
<li><p>How do I figure out the sample size of th... | g65344 | [
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0... |
<p>This question got me thinking about the meaning of variance: <a href="http://stats.stackexchange.com/questions/85387/intuition-behind-standard-deviation/85430#85430">Intuition behind standard deviation</a>. </p>
<p>Variance of a set of data is calculated the same way that the <a href="https://en.wikipedia.org/wiki/... | g49723 | [
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<p>Not sure if this would be the right place to ask...but I am attempting to calculate a topological overlap measure (TOM) matrix using R. I'm running into a problem with a likely simple solution. </p>
<p>Basically, I am not sure how to interpret the matrix notation for the TOM matrix. An example would be:</p>
<p>$... | g65345 | [
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<p>Consider any arbitrary estimator called $\hat{M}$ (e.g., regression coefficient estimator or specific type of correlation estimator, etc) that satisfies the following asymptotic property:</p>
<p>$$\boxed{\sqrt{N}(\hat{M}-M) \overset{d}{\to}\mathcal{N}(0,\sigma^2)}\,\,\,\,\,\,\,\,\,\,\,\,(1)$$</p>
<p>which implies ... | g65346 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/45825/what-hypothesis-for-a-is-better-than-b">What hypothesis for A is better than B?</a> </p>
</blockquote>
<p>Consider the Pearson correlation estimate $r$. I want to do a hypothesis test. </p>
<p>$$\te... | g49724 | [
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0.038365911692380905,
0.028547290712594986,
0.0... |
<p>I plan to use libSVM for a one-class svm problem, but I'm not sure about the meaning of <code>nu</code> in <code>svm_parameter</code>. </p>
<p>Does it mean the probability that a test point lies <em>outside</em> of a set S (estimated from the training data) equals <code>nu</code>?</p> | g28803 | [
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<p>I'm looking at Fisher's LDA on various datasets on UCI ML repository and trying to see where LDA might perform badly. One reason I can think of is if the data distribution is not a multi-variate normal distribution. This is from the fact I read in a book where you apply LDA on multivariate normal distribution. Is th... | g37449 | [
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0.014... |
<p>In ridge regression we know that</p>
<p><img src="http://i.stack.imgur.com/3YeSy.jpg" alt=""></p>
<p>as an estimate of $\beta$ and this gives the minimum sum of squares of the residuals:</p>
<p><img src="http://i.stack.imgur.com/1vkIm.jpg" alt=""> </p>
<p>And we know that</p>
<p><img src="http://i.stack.imgur.c... | g49725 | [
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0.0... |
<p>My research relates to situations in which individuals make a quantitative estimate and then make a second quantitative estimate, perhaps after some manipulation. Minimally I am interested in comparing: </p>
<p>A) The error of a first estimate<br>
B) The error of a second estimate<br>
C) The error of the average of... | g65347 | [
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0.04431375116109848,
0.012... |
<p>I am very new to Chi square goodness of fit tests but have done a fair bit of research.
Basically, I have the following 12 data points:</p>
<p>7392,
7656,
7241,
6164,
4984,
4664,
15262,
17053,
21814,
5094,
4581,
10500. </p>
<p>And I would like to test the assumption that a Lognormal($\mu$=9.11,$\sigma$... | g65348 | [
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<p>When preparing data for use with Covariance-based Structural Equation Modeling (CB-SEM), what are the different effects of replacing missing data with mean or median? When is one of them more appropriate than the other? Is any of them generally recommended?</p> | g65349 | [
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<p>A (<a href="http://www.math.wpi.edu/saspdf/stat/chap39.pdf" rel="nofollow">SAS documentation file</a>) (page 1906) on "The LOGISTIC Procedure" gives the following procedure-</p>
<pre><code>proc logistic;
model r/n=x1 x2;
run;
</code></pre>
<p>Here, n represents the number of trials and r represents the number of e... | g65350 | [
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0.... |
<p>This may well be a textbook question - I am not a statistician and just need to solve a practical problem - I will be grateful for any pointers to literature.</p>
<p>There is a $M\times N$ matrix $P$ defined by (matrix) multiplication of vectors $X$ and $Y$ (with lengths $M$ and $N$); that is, $P=XY'$. Here $X$, $Y... | g65351 | [
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... |
<p>I have one paired data from 7 patients:
$$(X_i ,Y_i)=\{(5,1),(-2,-4),(4,2),(-6,-3),(-3,-3),(-5,2),(3,1)\},\quad (i=1,\ldots, 7)$$</p>
<p>where $X$ means placebo $Y$ means the test drug.</p>
<p>My classmate asked me can we have permutation test for the sign statistics to identify $X < Y$.
I think the <a href="ht... | g23879 | [
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0.03822958469390869,
-... |
<p>In a project on software measurement, we plan to use aggregating statistics (e.g., Gini) to describe the concentration of certain observed program attributes (size) among program units (e.g., modules, functions). This is a purely exploratory, descriptive effort (e.g., no hypothesis testing involved).</p>
<p>We are ... | g23880 | [
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0.... |
<p>I have data from 8 subjects collected at 5 time points. I would like to see if there is a difference between time points (1 + 2) and (3 + 4 + 5) using either SPSS or Stata.</p>
<p>When in SPSS I use 'Analyze > GLM > Repeated Measures' I am able to specify the 5 time points, but I can not create contrasts. I can onl... | g65352 | [
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0.0027199911419302225,
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0.008147317916154861,
0.022876007482409477,... |
<p>I have some data:</p>
<p>x = c(0.0636931012704989, 0.0421033586843369, 0.0214721845269228,
0.038624779052474, 0.033235347720021, 0.0307709640052774, 0.0606316442337883,
0.0289958997354256, 0.0573689255248752, 0.044448618126441, 0.0164384406368751,
0.0357802024114138, 0.0133831663454831, 0.0329126088838874, 0.051... | g23881 | [
-0.019277308136224747,
0.020236844196915627,
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0.07226581126451492,
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0.021891223266720772,
0.012073546648025513,
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-0.013689174316823483,
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... |
<p>I have a bunch of records, T in total. I want to know how many of these I can get away with analyzing in order to extrapolate the analysis to the entire population T.</p>
<p>I know this is a basic question and largely depends on how much error I can accept, but can anyone tell me the math?</p> | g65353 | [
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<p>My aim is to detect malware by testing it with the extracted features. I have extracted the binary features of 150 malware files and 150 benign files by using the hex editor tool for unpacking the files and Netbeans for generating a dataset in an Excel sheet. Now I have Features of malware and benign datasets in sep... | g65354 | [
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0.053915... |
<p>I am running a simple OLS.</p>
<ul>
<li><strong>Dependent Variable:</strong> Population Change In A Congressional District After An Election</li>
<li><strong>Independent Variable:</strong> Who won the election: Democrat, Republican, or, Independent (Categorical)</li>
</ul>
<p>I've created dummies variables for the... | g65355 | [
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0.0... |
<p>Thanks to Zach's code.</p>
<p>I run R code as below and get error that cold not find "trainControl and train function" </p>
<pre><code>#Use the same CV-folds for each model
require(caret)
myControl <- trainControl(method='cv', number=10, index=createFolds(y, k=10))
#Fit models
model_rpart <- train(X, y, met... | g47898 | [
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0.025904400274157524,
... |
<p>How can I generate two correlated $AR(1)$ data series with given correlation between $d_{1,t}$ and $d_{2,t}$, $r_{12}$, where $\rho_{12}$ is correlation between the two error series
$$d_{1,t}=\mu+\phi_1d_{1,(t−1)}+e_{1}(t)\quad\quad d_{2,t}=\mu+\phi_2d_{2,(t-1)}+e_{2}(t)$$</p>
<p>$e_1$ and $e_2$ are not the same an... | g42809 | [
0.006957068108022213,
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0.011720252223312855,
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0.006301692686975002,
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0.016646770760416985,
0.04261115565896034,
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<p>I am trying to fit a model which is similar to the </p>
<pre><code>fm2orth.lm<-lme(distance~age,data=OrthoFem, random=~1|Subject)
</code></pre>
<p>and did </p>
<pre><code>summary(fm2Orth.lm)
</code></pre>
<p>my output had these parts </p>
<ol>
<li>Aic/BIC </li>
<li>Random Effects </li>
<li>Fixed Effects t... | g65356 | [
0.011898347176611423,
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0.051061082631349564,
0.03302845358848572,
... |
<p>Would any R expert explain the predic function in the randomforest package to me?</p>
<p>I want to get two prediction results for numberic response variable A and B seperately from following regression</p>
<pre><code>result <-randomforest(A + B ~ C + D + E, data = dataset)
predict(result)
</code></pre>
<p>I ca... | g49726 | [
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0.005878919269889593,
0.010581479407846928,
0.0024076818954199553,
... |
<p>I've created an ARIMA (0 1 1)(0 1 2)12 model for our electricity costs. I have 44 months of monthly data, and have used X-12-ARIMA to do the model fitting. (I get similar results in R, it's just easier to use X-12-ARIMA and it gives a LOT of diagnostic output.) X-12-ARIMA allows you to enter a level shift easily, fo... | g65357 | [
0.029098376631736755,
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0.001960319234058261,
0.05281151458621025,
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0.05078260228037834,
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<p>I have a question that has been confusing me ever since I took econometrics last year. What does the "root MSE" mean in stata output when you regress a OLS model?</p>
<p>I know that it translates into "root mean squared error", but which variable's mean squared error is it after all, and how is it calculated? Can a... | g65358 | [
0.04512273147702217,
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0.023508505895733833,
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0.013173240236938,
0.04245327413082123,
0.008871822617948055,
-0.03114577755331993,
-0.015103543177247047,
0.07759935408830643,
0.10949557274580002,
-0.029... |
<p>I am reading about linear discriminants, and have encountered a phrase that I have no idea about. The phrase says that a decision region constructed in a certain way, is "singly connected and convex", I want to know in really simple terms what this means. I have an idea of what convex means in that a convex function... | g250 | [
0.017982471734285355,
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0.01454186998307705,
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0.042864736169576645,
0.08435232192277908,
0.018... |
<p>I am lost in normalizing, could anyone guide me please.</p>
<p>I have a minimum and maximum values, say -23.89 and 7.54990767, respectively.</p>
<p>If I get a value of 5.6878 how can I scale this value on a scale of 0 to 1.</p> | g49598 | [
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0.01925024576485157,
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0.002878582337871194,
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-0.017313512042164803,
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0.0053263260051608086,
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0... |
<p>I have the following question:</p>
<blockquote>
<p>Given a mean of 11 and a standard deviation of 2, with a non-normal
distribution, can you determine the % of numbers that are between 8 and
12?</p>
</blockquote>
<p>My guess is no, because the distribution could be weighted on the left and right... but I'm ... | g65359 | [
0.01973644271492958,
0.06663442403078079,
0.0075447107665240765,
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0.015096901915967464,
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0.039598800241947174,
0.02448948472738266,... |
<p>I am new to data mining and currently working on an online news article from TOI. My aim is to get some useful information out of this text which is not clear when you read the article and the most important things mentioned in it.</p>
<p>I am done with document processing on the article "TOI manifesto" which I hav... | g65360 | [
0.05113062262535095,
0.02808586321771145,
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0.03479491546750069,
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0.028157707303762436,
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0.04464036598801613,
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0.08460372686386108,
-... |
<p>I recently spoke to a large qualitative analysis company who were working on in-depth analysis of the potential customers of train company. I asked them how they chose the people to include in their sample, they said, that they picked them at random from list of people in the region, but they also said that had pred... | g43878 | [
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0.014173588715493679,
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0.012996286153793335,
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0.01651054620742798,
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0.025954099372029305,
0.02414107136428356,
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0.03... |
<p>How to deal with HMC that has continuous states?</p>
<p>Any papers, links, materials that explain the solution?</p> | g65361 | [
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0.011018898338079453,
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0.039730772376060486,
... |
<p>I am looking for theoretical resources (books, tutorials, etc.) to learn about making sound statistical inferences given (plenty of) multivariate website conversion data.</p>
<p>I'm after the math involved, and cannot find any good non-marketing stuff on the web. The sort of questions I want to answer: how much imp... | g23890 | [
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0.029910504817962646,
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0.06796101480722427,
0.0241... |
<p>I have been reading Mostly Harmless Econometrics and have been won over by the virtues of splitting my instrument into groups. In particular, I have a continuous variable as an instrument representing percent and would like to split it into 3 groups (0-33%, 34-66%, 67-100%) and use dummies to indicate each group, i.... | g65362 | [
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0.047880787402391434,
0.012434340082108974,
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0.00006005617251503281,
0.007502650376409292,
-0.02623509243130684... |
<p>Given a matrix whose entries consist of only 1's and 0's, I would like to come up with a measure of how "ordered" the matrix is, in some sense. This exact question was posed here:</p>
<p><a href="http://stats.stackexchange.com/questions/17109/measuring-entropy-information-patterns-of-a-2d-binary-matrix">Measuring ... | g46495 | [
-0.08992208540439606,
0.0025520925410091877,
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0.016331834718585014,
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-0.02364390343427658,
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0.04876025393605232,
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-0... |
<p>I have a question: Suppose I have a logistic regression model, with data from 2008 to 2011. Because of some reasons like I cannot collect all data, only a sample(or subset) of the data was used to build the model, for example, bads and goods ratio is 1:4. And now I have all 2012 and 2013 data. The bads goods for 201... | g65363 | [
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0.023128090426325798,
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0.01488027535378933,
0.06973028928041458,
0.03594980388879776,
0.056939747184515,
-0.02420... |
<p>I have two distributions which are derived from 2 separate sets of data. These distributions are not normal, and it is not clear at this point if they belong to any family of known pdfs (they are not symmetric either). Given a data point, I need to decide which distribution it is most likely to belong to. If these w... | g49895 | [
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0.005356230773031712,
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0.01745472103357315,
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0.031073663383722305,
0.0007568337605334818,
0.03604736924171448,
... |
<p>What are some good introductory materials for learning non-linear regression modeling? Bonus points for anything freely available. Thanks!</p> | g65364 | [
0.01479677390307188,
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0.02464449219405651,
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0.020578479394316673,
0.052584633231163025,... |
<p>I have RNA-seq data from 9 samples and around 15,000 genes. I know that these 9 samples consist of varying proportions of two cell types, each with their own expression profile. I am using non-negative matrix factorization with a rank of 2 to determine the cell-type ratios in each sample. In other words, I use NM... | g65365 | [
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0.027773862704634666,
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-0.016008444130420685,
-0.010121770203113556,
-0.001834983704611659,
0.00811361335217952... |
<p>I tried to normalize many set, which each set consists of 12 values. I want to normalize it into range between 1 and -1. However, the highest value is unclear because the value can be trillion, or even more. I code it using java. </p>
<p>can somebody help me what to do? I tried to normalize it using standard deviat... | g23899 | [
-0.01356574334204197,
0.07762224972248077,
-0.022106830030679703,
-0.016878793016076088,
0.0072314562276005745,
0.011055028066039085,
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0.002333260839805007,
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-0.019212055951356888,
-0.0175222996622324,
0.02176804654300213,
-0.022725004702806473,
0... |
<p>How many individuals do I need to compare 3 AUC which are computed from the
same set of patients?</p>
<p>Is there a R program or some other program available?
There are many programs for computing the sample size when comparing 2 AUC, but I
have found none for more than two.</p> | g35188 | [
0.02830774337053299,
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0.005429974757134914,
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0.030509892851114273,
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0.03895308077335358,
0.0416138730943203,
0.0353052094578743,
-0.03... |
<p>I've scoured Google and this site and I am still confused about the lmer function in the lme4 library.</p>
<p>I have some data collected from different psychiatric wards, which have a multilevel structure. To simplify, I'll pick two level 2 and two level 1 variables, although I actually have a few more.</p>
<p>Lev... | g37968 | [
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0.041790083050727844,
0.029653314501047134,
0... |
<p>I have data from 40 people, each measured once in 2 conditions. For reasons tangential to my question I'm not comfortable using parametric analyses to compare the two conditions, so I'm employing bootstrapping. However, when I run a bootstrap analysis (resampling people with replacement, computing condition means, t... | g37666 | [
0.006741814315319061,
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0.010625245049595833,
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0.06626980751752853,
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-... |
<p>An experiment I conducted recently used a 2 (between participants) x 3 (within participants) design. That is, participants were randomly allocated to one of two conditions, and then completed three similar tasks each (in a counterbalanced order). </p>
<p>In each of these tasks, participants made binary choices (2AF... | g65366 | [
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0.0616452656686306,
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0.00608112383633852,
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0.02521737851202488,
-0.0... |
<p>I am designing a Hybrid Monte Carlo sampling algorithm for <a href="http://code.google.com/p/pymc/">PyMC</a>, and I am trying to make it as fuss free and general as possible, so I am looking for good advice on designing an HMC algorithm. I have read <a href="http://www.cs.utoronto.ca/~radford/ham-mcmc.abstract.html"... | g65367 | [
0.016822654753923416,
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... |
<p>I have a data having 2 continuous and 4 categorical variables. Each categorical variable has 3 levels. I want to know how to include the variables in the model. I am using SPSS</p>
<p>Variables:</p>
<ol>
<li>Sales - Dependent Variable</li>
<li>Retail Price</li>
<li>Location : TX, CA, PY</li>
<li>Display Location ... | g65368 | [
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<p>I understand that Levenberg-Marquardt adjustment is about adding $\lambda \times\; I$ to second derivative of the log likelihood function, where $I$ is the identity matrix
$$-[l''(\theta | Y) - \lambda I] \quad \text{such that it becomes positive definite}$$</p>
<p><strong>My question is:</strong> How should we cho... | g65369 | [
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<p>I'm using a mixed model in <code>R</code> (<code>lme4</code>) to analyze some repeated measures data. I have a response variable (fiber content of feces) and 3 fixed effects (body mass, etc.). My study only has 6 participants, with 16 repeated measures for each one (though two only have 12 repeats). The subjects are... | g65370 | [
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<p>Is there a solution coded in R to estimate models of the form</p>
<p>$$
y_{igt} = \alpha_i + P_{gt} + \beta_1y_{igt-1}+ \beta_2y_{igt-2} + X_{igt}'\gamma + \epsilon_{igt}
$$
??</p>
<p><code>plm</code> offers the <code>pgmm</code> package, which implements the Arellano-Bond estimator, but it doesn't seem able to ha... | g4760 | [
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<p>In many statistical problems, I see the following formulation for maximizing rewards: Assuming that my total reward $R$ is the sum of individual rewards $R$:</p>
<p>$\underset{\textbf{x}}{\operatorname{argmax}}E[R_T] = \underset{\textbf{x}}{\operatorname{argmax}} \left(E[R_1] + E[R_2] + E[R_3]\right)$</p>
<p>where... | g65371 | [
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<p>I'm studying the effect of various criminal case and court district characteristics on sentence lengths. I was planning on running xttobit in Stata because I have individual defendants/cases within federal court districts and a censored sentence length outcome. I have both an upper and lower limit. A prison sentence... | g65372 | [
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<p>I would like to estimate power of the following problem. I am interested in comparing two groups that both follow e.g. Weibull distribution. So, group A has two parameters (<code>a1, b1</code>) and two parameters has group B (<code>a2, b2</code>). By simulating random variables from distribution of interest (assumi... | g65373 | [
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<p>I have weekly data which I am considering as reference. So Mondays trend for example.. orders will kind of serve as valid data to make predictions for orders throughout the day for every Monday. I looked at the <code>lm()</code> and <code>predict()</code> functions in R, but it seems that they just predict based my ... | g65374 | [
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<p>There is a filter in Weka called "Add Classification". One can choose a classification algorithm and then can get the classification labels provided by the model generated by the algorithm, the distribution of the classes, and errors it is making. Then, one can add these information (classification labels, class dis... | g65375 | [
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<p>The (generalized version) of the problem I'm trying to solve: Say you're observing the surface of a puddle while it's raining. There are various sized ripples occurring wherever a raindrop hits the puddle, which happens with a regular frequency. Now imagine you throw a pebble at the puddle; how would you determine, ... | g65376 | [
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<p>I have 5 individuals. I measure variable X and Y of each one of them over time (on 5 different time points). I want to find out if there are any correlations between X and Y over time and show the same trend for all 5 individuals.</p>
<p>The data looks like this (just an example, not my real data):</p>
<pre><code>... | g23911 | [
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0.... |
<p>I am working on Text classification problem (Sentiment Analysis), and i am having a dataset of movie reviews which contains 1000 positive and 1000 negative reviews, and for classification of those reviews in positive or negative, i am using Random Forest classifier(Tool : WEKA).</p>
<p>In WEKA i am using the defaul... | g65377 | [
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<p>I am not sure how to ask this question without giving an example. </p>
<p>I am trying to measure the "cleanliness" of office buildings. I have two variables that try to measure this. </p>
<p>Variable one is a person who inspects a random sample of the offices in a building and rates the cleanliness of each offic... | g65378 | [
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<p>We compare the performance of >2 classifiers. Samples are drawn from n-fold cross-validations on the same data sets. We are aware of the fact that cross-validation makes the samples dependent, because training sets overlap. Nevertheless, this is not our main concern here.</p>
<p>Because the same data set is used fo... | g65379 | [
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<p>I thought I understood Adaboost, until code analysis made me realize that sample_weight is not an array of the feature weights... and after further investigation I am left confused as to how multidimensional features are even utilized in Adaboost without stumps or tree.</p>
<p>Is the implicit definition of a weak l... | g65380 | [
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... |
<p>I have used Gamma distribution in my GLM with identity link. I want to do backward model selection with drop1 command in R as described in Zuur, 2009. But I get this warning message:</p>
<pre><code>Error: no valid set of coefficients has been found:
please supply starting values
In addition: Warning messa... | g23913 | [
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<p>I read multiple times that the it is crucial in regression to (1) look at the "mean structure", and (2) at the "mean/variance relationship".</p>
<p>Alas, I have absolutely no idea what that means, and how it is connected to the assumptions of various regression (e.g. homoscedasticity and normal distribution in OLS,... | g65381 | [
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<p>Consider the ARMA(1,1) process
\begin{align}
y_t=a_1y_{t-1}+b_1\epsilon_{t-1}+\epsilon_t,
\end{align}
and assume $\epsilon_t$~$N(\mu_t,\sigma_t)$. And $\mu_t$ and $\sigma_t$ are all known.</p>
<p>$f(y_t|y_{t-1})$ and $f(y_t>c|y_{t-1})$ are easy to calculate. For instance $f(y_t|y_{t-1})$ is the Normal density wi... | g65382 | [
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<p>I was ask to do a linear regression analyses of my variables. I have Reaction times. Can you recommend me a linear regression analysis (hierarchical?) and tell me whether I should transform my raw data into logarithms before that analysis? </p>
<p>My reaction times are in milliseconds.</p> | g65383 | [
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<p>So I have performed a logistic regression on a data set with multiple predictors. I want to graphically represent the relationship between the outcome and only one of the predictors. What would be the best way of doing this?</p>
<p>I am having a hard time figuring out how to graphically show the effect that predict... | g65384 | [
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<p>I have a dataset I would like to analyze and plot
It consists of 100 binary variables (0/1) for about 2,000,000 observations
There is absolutely no quantitative variable, nor anything I could use as an explained variable for a regression analysis.</p>
<p>Actually, the dataset represents the patronage of 2 billion c... | g65385 | [
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<p>I am reading <a href="http://rads.stackoverflow.com/amzn/click/0262018020" rel="nofollow">Machine Learning - A probabilistic Perspective</a> by Kevin Murphy and in chapter 6.5 the author discusses <a href="http://en.wikipedia.org/wiki/Empirical_risk_minimization" rel="nofollow">Empirical Risk Minimization</a>, and p... | g23917 | [
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<p>I have a run an unbalanced 2x2x2x2 Type II ANOVA in R and am having trouble following up on the results. Here is the output:</p>
<pre><code> Effect DFn DFd F p p<.05 ges
2 cond 1 127 3.2359349424 0.074414031 0.0110769653158
3 sf 1 127 1.69... | g23918 | [
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0.01... |
<p>My understanding is that a <a href="http://en.wikipedia.org/wiki/Hazard_ratio">hazard ratio</a> from a Cox proportional hazards model compares the effect on the hazard rate of a given factor to a reference group. How would you report that to an audience that doesn't know statistics?</p>
<p>Let's try to phrase an e... | g65386 | [
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<p>I have a set of data that contains cases and controls. I would like to divide the cases by a particular phenotype before running my tests, to see how these groups differ (but not necessarily to directly compare them). My feeling is that I must also randomly divide the controls between these two groups of cases befor... | g23921 | [
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<p>Suppose we have $100$ people and we obtain the average blood pressure $x$. Now suppose we have another group of $40$ people and they have an average blood pressure $\approx x$. How do we quantify the fact that the second experiment is more "efficient" than the first experiment? Would we do a power analysis? What wou... | g43912 | [
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<p>I am beginner in R. I had found in the literature that prior to performing kriging on the data, the distribution has to be investigated to check if it is Gaussian.</p>
<p>So, in order to check if the data follows Gaussian I plotted the quantile-quantile plot of rainfall for all days using data from 50 stations. </p... | g49427 | [
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... |
<p><strong>Model</strong>:</p>
<p>A vector $X=(X_1, X_2, X_3)$ that follows a trinomial distribution with parameters $p=1/3$ and $n$.</p>
<p>(I have a coin with three sides $S1$, $S2$, $S3$). I flip the coin $n$ times. The coin has a probability $p=1/3$ to be flipped to the side $S1$, and similarly with $S2$ and $S3$... | g65387 | [
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0.010562008246779442,
... |
<p>Could you suggest more recent reviews or book on the methods for handling missing data (i.e. multiple imputation)?</p>
<p>I want to know the challenges in this field.</p> | g29169 | [
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<p>I have 9 categories of response variable, and facing interpretation problems. </p>
<ul>
<li>Could I use this ordinal data as continuous data?</li>
<li>If not then please refer me to some example with more than 5
categories.</li>
</ul>
<p>Thanks!</p> | g39229 | [
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<p>A)
I have:
a pre and post measurement on 7 ordinal/scale variables for every participant (=student in classroom)
1 intervention
5 classrooms of students
3 teachers implementing the intervention</p>
<p>I want to know whether pre and post differences of each classroom are significant, and whether differences of int... | g65388 | [
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... |
<p>I haven't found a satisfactory answer for this problem by reading previous related posts. There are a total of $10,000,000$ observations with the following observed and expected frequencies:</p>
<p><img src="http://i.stack.imgur.com/G0ABT.png" alt="enter image description here"></p>
<p>A goodness-of-fit $\chi^2$-t... | g65389 | [
-0.012421736493706703,
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... |
<p>I would be really glad if someone could help me with the following problem:</p>
<p>Let us consider a circular environment with $R=1$ and $n$ points uniformly distributed within the circle's area.</p>
<p>All these vertices are assigned a range (think of sensors being capable of transmitting data wirelessly from one... | g65390 | [
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0.04045286774635315,
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-... |
<p>Why is it the case that when I run logistic regression with one categorical predictor, my regression is not significant whereas if I run the logistic regression with the same variable except it is continuous, the logistic regression automatically becomes significant?</p> | g65391 | [
0.007497344631701708,
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0.033828254789114,
0.050297193229198456,
0.041... |
<p>I am writing a CS paper, I usually would assume anyone knows what a boxplot is in a technical domain. Is a reference required or are boxplots knowledge that can be assumed? What is essential to explain about a boxplot in this setting?</p> | g65392 | [
0.033461328595876694,
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0... |
<p>This is something from Chris Bishop's book and I want to confirm that I have understood this correctly.</p>
<p>So, suppose we have a joint distribution between two RVs as:</p>
<p>$$
P(a, b) = P(a|b)P(b) = P(b|a)P(a)
$$</p>
<p>Now, suppose that $b$ is observed, can I write the joint distribution as:</p>
<p>$$
P(a... | g35196 | [
0.038593873381614685,
-0.041053906083106995,
-0.0019029286922886968,
-0.05189767852425575,
0.016188841313123703,
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<p>I have 50 values set as "true" in a simulation and attempts to recover these "true" parameters using 2 different models. Here's 3 (instead of 50) runs just to show the data layout (these are made up for illustration).</p>
<pre><code>Run , "true" parameter , estimate model 1 , estimate model 2
1 , 10 ... | g23926 | [
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-0.020476846024394035,
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0.014894474297761917,
0.028729531913995743,
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0.03180642053484917,
-0... |
<p>I am trying to compare two binary logistic regression models. The dependent variable is disease_state and it can be 0=healthy, 1=disease for each sample.
The first model's predictor variable is the presence of variation in a set of genes (has_var, 0=no variation, 1=variation), the second model's is a 3-levels varia... | g65393 | [
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-0... |
<p>Some research has shown that in linear regression applications the Mahalanobis distance approach can be used to perform regressions that lower the influence of outliers. The idea is that in the regression every observation is given a weight as an inverse of the Mahalanobis distance. </p>
<p>I see that there is a pa... | g43927 | [
0.02041292004287243,
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-0.017848754301667213,
0.030087461695075035,
0.02103063091635704,
0.047562334686517715,
-0... |
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