question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I've read that homoskedasticity means that the standard deviation of the error terms are consistent and don't depend on the x-value.</p>
<p>Question 1: Can someone explain intuitively why this is necessary? (An applied example would be great!)</p>
<p>Question 2: I can never remember whether it's <em>hetero-</em> o... | g59279 | [
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<p>I want to estimate a VAR model based on the Dufour and Engle <a href="http://weber.ucsd.edu/~mbacci/engle/291.pdf" rel="nofollow">paper</a> "Time and the Price Impact of a Trade" (2000).</p>
<p>There, the parameter $ b_{i} $ of the endogenous variable $ x_{i} $ is dependent on the strictly exogenous variable $ T_{t... | g59280 | [
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<p>I want to use Generalized Cross Validation to compute the optimal ridge parameter for a ridge regression.</p>
<p>The formula due to Golub et al (1979) is</p>
<p>GCV(k)=(1/n Sum_i=1^n e_i(k)^2)/(1/n Sum_i=1^n(1-h_ii(k)))^2</p>
<p>where e_1(k)....e_n(k) are the residuals from applying the ridge regression for a giv... | g59281 | [
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<p>I'm dealing with some data where there are some infrequently occuring categorical variables related to a binary prediction target. </p>
<p>For example marketing partners... some send 1000s of leads but many others send less than 10 a minuscule number in a data set with 20K+ examples.</p>
<p>Typically, we deal with... | g59282 | [
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<p><strong>Theorem</strong></p>
<p>Suppose $X_n \stackrel{P}\to X\quad \text{and}\quad Y_n \stackrel{P}\to Y $. Then $X_n+Y_n \stackrel{P}\to X+Y $.</p>
<p><strong>Proof</strong></p>
<p>Let $\epsilon >0 $ be given. Using the triangle inequality, we can write $$ | X_n-X|+|Y_n-Y| \geq |\left( X_n+Y_n \right) -\left... | g14736 | [
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<p>I am to use the Squared Exponential kernel (SE) for Gaussian Process Regression. The advantages of this kernel are: 1) simple: only 3 hyperparameters; 2) smooth: this kernel is Gaussian. </p>
<p>Why do people like 'smoothness' so much? I know that the Gaussian kernel is infinitely differentiable, but is that so imp... | g59283 | [
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<p>When you predict a fitted value from a logistic regression model, how are standard errors computed? I mean for the <em>fitted values</em>, not for the coefficients (which involves Fishers information matrix).</p>
<p>I only found out how to get the numbers with <code>R</code> (e.g., <a href="https://stat.ethz.ch/pi... | g59284 | [
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<p>I am using stata, and running a regression with robust standard errors.
I want to test the Heteroscedasticity after running the regression with robust standard errors, and to compare this to before the regression was run using this facility?</p>
<p>Is this possible in anyway? </p> | g59285 | [
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<p>Here is a little background about my situation: my data refer to the number of prey successfully eaten by a predator. As the number of prey is limited (25 available) in each trial, I had a column "Sample" representing the number of available prey (so, 25 in each trial), and another called "Count" which was the numbe... | g3256 | [
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<p>I am a student taking my first Statistics course now. I am confused by the term "test statistic". </p>
<p>In the following (I saw this in some textbooks), $t$ seems to be a specific value calculated from a specific sample.
$$
t=\frac{\overline{x} - \mu_0}{s / \sqrt{n}}
$$</p>
<p>However, in the following (I saw th... | g59286 | [
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<h2>Situation:</h2>
<p>n possibilities each have their own probability of happening, and their own payout when they do. </p>
<p>So expected payout $E_n$ is $\sum\limits_{i=1}^n \text{probability}_i*\text{payout}_i$</p>
<p>And the expected variance is $\sum\limits_{i=1}^n ( \text{payout}_i- \text{expected payout})^2... | g59287 | [
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<p>When we run a regression model (say OLS for simplicity) of y ~ x, we might have to use several control variables say z1 and z2. Now our model is y ~ x + z1 + z2, we may believe that z1 and z2 are not perfect controls then we introduce fixed effect dummies.</p>
<p>Now our model is y ~ x + z1 +z2 + fixed effects; but... | g452 | [
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<p>I have a regression model with two significant main effects and a significant interaction. I'd like to calculate an effect size for one of the main effects. </p>
<p>I'm using the package <code>compute.es</code> in R. I'm not sure whether I should use the empirical means and standard deviations or the t-value from t... | g43939 | [
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<p>Is it possible to obtain a positive correlation between a regressor and a response (<code>+0,43</code>) and, after that, obtain a negative coefficient in the fitted regression model for this regressor?</p>
<p>I'm not talking about changes in the sign of the regressor among some models. The coefficient sign always r... | g49342 | [
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<p>I need to compare microarray data, where all of the "cases" were hybridized in one batch and all of the "controls" in another, so I have no way of removing this batch effect. </p>
<p>What would be the best strategy to detect differentially expressed genes (if at all possible)?</p> | g59288 | [
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<p>I have been given this task and was stumped. A colleague asked me to estimate the $x_{upper}$ and $x_{lower}$ of the following chart:</p>
<p><img src="http://i.stack.imgur.com/FLDQU.png" alt="enter image description here"></p>
<p>The curve is actually a cumulative distribution, and x is some kind of measurements. ... | g14745 | [
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<p>I've just started learning R, but I feel that I'm using it only as a normal procedural language without taking advantage of some built-in functions and data structures.</p>
<p>As an example I wrote a function that calculates repayments for mortgage with an option of specifying list of overpayments to reduce monthly... | g59289 | [
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<p>I'm struggling to understand how the predict function works and can be used with out of sample data. For instance the following code...</p>
<pre><code>my <- data.frame(x=rnorm(1000))
my$y <- 0.5*my$x+0.5*rnorm(1000)
fit <- lm(my$y ~ my$x)
mySample <- my[sample(my, 100),]
predict(fit, mySample)... | g11007 | [
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<p>Can anyone give the intuition behind of the relationship between these two? I see a lot of proofs in books, but no real intuition. </p>
<p>Thanks</p> | g59290 | [
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<p>I have 3800 stocks for which I calculate their return correlations. So I end up with a 3800 by 3800 matrix. Each stocks is related in some way to all the other 3799 stocks. For each stock, I create seven groups out of 3799 stocks based on their relatedness. So say for stock A, <code>group 1</code> (closest in relate... | g59291 | [
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<p>I have a problem similar to what was discussed <a href="http://mathematica.stackexchange.com/questions/13054/estimate-error-on-slope-of-linear-regression-given-data-with-associated-uncertai">here</a>: I have a dataset (x_i,y_i) with y-error which is nonuniform over the interval of interest. I want to fit a line to t... | g59292 | [
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<p>I have an experimentally observed distribution that looks very similar to a gamma or lognormal distribution. I've read that the <a href="http://en.wikipedia.org/wiki/Log-normal_distribution">lognormal distribution</a> is the maximum entropy probability distribution for a random variate $X$ for which the mean and var... | g59293 | [
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<p>As a (perhaps contrived) example, let's say we want to discover from some empirical data Coulomb's law for an electric field:</p>
<p>$$F = \frac{1}{4 \pi \epsilon_0} \cdot \frac{|q|}{r^2}$$</p>
<p>In this case we would have a matrix whose columns include force $F$, charge $q$, and radius $r$; as well as perhaps so... | g59294 | [
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<p>I have the following relationships</p>
<p>logY ~ logX1 + logX2 + logX3 + logX4 + logX5 </p>
<p>and</p>
<p>X1 ~ Z1 + Z2 + Z3 + Z4 + Z5</p>
<p>X2 ~ Z1 + Z2 + Z3 + Z4 + Z5</p>
<p>X3 ~ Z1 + Z2 + Z3 + Z4 + Z5</p>
<p>where Y and Z1, Z2, Z3, Z4, Z5 are endogenous (Say while the Z's play a role in determining Y, the v... | g14750 | [
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<p>I'd like to know if there is statistical techniques that aims to find the rhythm/tempo of a music based on audio signal :</p>
<p><img src="http://i.stack.imgur.com/KgbnR.png" alt="Audio signal"></p> | g59295 | [
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<p>I would like to study how the death of a respondent's parent affects his personality (or whatever DV). I have an age of respondent, and also an age when respondent lost his parent. The problem is that these records are available only 23 years back. That is if somebody lost his parents 25 years ago this information i... | g59296 | [
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<p>When I learn several classifiers for a task and want to compare their performance on it, I thought about calculating several performance measures, such as:</p>
<ul>
<li>sensitivity</li>
<li>specificity</li>
<li>positive and negative predictive value</li>
<li>...</li>
</ul>
<p>Then of course I can compare the singl... | g59297 | [
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<p>When discussing probability distribution, I always read something such as excess kurtosis, positive kurtosis, positive skewed and negative skewed. What exactly do these concepts indicate? In practical applications, such as market return or something else, what can these characteristics tell us?</p> | g14755 | [
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<p>One can define the probability distribution:
$$
p(\theta; \alpha, \theta_0) = \frac{ e^{ \alpha \cos( \theta-\theta_0) }}{ 2 \pi I_0(\alpha)}
$$
over an angular variable $\theta \in [0,2 \pi]$. By what name(s) is this distribution called?</p>
<p>($I_0$ is the modified Bessel function and serves to normalize the di... | g59298 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/16665/how-can-i-get-a-significant-overall-anova-but-no-significant-pairwise-difference">How can I get a significant overall ANOVA but no significant pairwise differences with Tukey's procedure?</a> </p>
<... | g49322 | [
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-0.035521142184734344,
0.027054814621806145,
0.004960001911967993,
-0.020665811374783516,
0.005055672954767942,
-0.016308525577187538,
-0.0072036683559417725,
0.015658024698495865... |
<p>I have often read that there is a huge connection between the normal distribution and several other distributions. But these were only mathematical explanations.</p>
<p>What's the "real" connection between these 3 distributions (normal, $\chi^2$, and F)? </p> | g59299 | [
0.03634820505976677,
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0.012420523911714554,
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-0.03232750669121742,
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0.02731664665043354,
-0.00... |
<p>Are there some nice introductions to
IDI (integrated discrimination improvement index), NRI (net reclassification index), multivariable likelihood ratios, Bayesian methods, biomarker validation, risk scores from multi-biomarker data? Where do they arise and how are they obtained or performed?</p>
<p>I guess the t... | g15351 | [
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0.004042660817503929,
0.009755531325936317,
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0.10250558704137802,
-0... |
<p>If you have a matrix with n rows and m columns, you can use SVD or other methods to calculate a <a href="http://en.wikipedia.org/wiki/Low-rank_approximation">low-rank approximation</a> of the given matrix.</p>
<p>However, the low rank approximation will still have n rows and m columns. How can low-rank-approximatio... | g14759 | [
0.014665843918919563,
0.009255646727979183,
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0.0253886915743351,
0.045772161334753036,
0.03... |
<p>I'm using R and the library TraMineR to do sequence analysis on social science data. I have computed an optimal matching (OM) distance matrix.</p>
<pre><code> [,1] [,2] [,3] [,4]
[1,] 0.00000 94.80628 110.00000 107.46826
[2,] 94.80628 0.00000 53.71086 78.02520
[3,] 110.00000 53.71086 0.00... | g59300 | [
0.03851165249943733,
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0.014177408069372177,
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0.009521679021418095,
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0.021936390548944473,
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0.05452795699238777,
-0... |
<p>I have one sample and three sub-samples and I would like to calculate the p-value for the hypothesis that the proportion in the sub-sample is not different from the proportion in another sub-sample or not different from the proportion in the sample. </p>
<p>The sample consists of counting how often there is agreeme... | g59301 | [
0.02213369496166706,
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0.029482288286089897,
0.024582453072071075,
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... |
<p>In my data, the response variable is ordinal and there are 16 predicting variables which are also ordinal. I plan to perform an ordinal regression. But before doing that I want to graphically show the relationship between the response and predictor variables. In regular regression where the variables are numerical, ... | g59302 | [
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0.001... |
<p><strong>Background:</strong> My dataset is small (3 to 10 values). But each set comes from 18 acquisitions of different areas of the same sample. So they would not be considered independent. But 3-10 values are too small to analyze whether the distribution is normal. And the raw values differ a lot between independe... | g59303 | [
-0.00041614813380874693,
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-0.02617696486413479,
0.023372717201709747,
0.03166232630610466,
0.001081251772120595,
... |
<p>Can you / how do you calculate the effect of a one-sample Wilcoxon signed-rank test?</p>
<p>Is there a way to perform the calculation in SPSS or another software package?</p> | g14761 | [
-0.010590089485049248,
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-0.03952864930033684,
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0.07650896161794662,
0.0009807501919567585,
0.03... |
<p>How can I analyze an within-subject full-factorial experiment with ordinal data from likert scale (with repetitions)? I would greatly appreciate your help.</p>
<p><strong>Study design</strong></p>
<p>Here is a description of the study design, below you can find the data we collected for clarity.
We conducted a <em... | g59304 | [
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0.0020660539157688618,
0.019012071192264557,
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0.008310266770422459,
... |
<p>We know that a paired <i>t</i>-test is just a special case of one-way repeated-measures (or within-subject) ANOVA as well as linear mixed-effect model, which can be demonstrated with lme() function the nlme package in R as shown below.</p>
<pre><code>#response data from 10 subjects under two conditions
x1<-rnorm... | g43954 | [
-0.020111849531531334,
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0.0016490693669766188,
0.011316421441733837,
0.005219994578510523,
... |
<p>I am modeling some data where I think I have two crossed random effects. But the data set is not balanced, and I'm not sure what needs to be done to account for it.</p>
<p>My data is a set of events. An event occurs when a client meets with a provider to perform a task, which is either successful or not. There a... | g59305 | [
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-... |
<p>I have four groups of plant treated with different temperatures and I conducted repeated measurement on their growth rate. I use ANOVA with Mixed Model to analyze the data by specifying both temperature (TEMP), time (TIME) and their interaction (Temp*Time) as fixed factor, I also include TIME as repeated factor usi... | g59306 | [
0.010861045680940151,
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0.022633425891399384,
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0.007978033274412155,
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0.0005262399208731949,
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... |
<p>I want to calculate: </p>
<p>$\operatorname{var}[\frac{b}{a} B(a-b)-b B(b)]$ with $b\leq a$ and $b\geq 0$; $B=$brownian motion.</p>
<p>I started like this: $(\frac{b}{a})^2 \operatorname{var}[ B(a-b)]+-b ^2 \operatorname{var}[ B(b)]+ 2 \operatorname{Cov}(B(a-b), B(b))$</p>
<p>Can someone help me here or comment ... | g14769 | [
0.0062323203310370445,
0.03496183454990387,
0.00606765691190958,
0.04669800400733948,
0.04182901978492737,
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0.07322140038013458,
0.004047950264066458,
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0.030513469129800797,
-0.03874800354242325,
0.07536597549915314,
0.03123762458562851,
0.07919966... |
<p>I know 2 approaches to do LDA, the <em>Bayesian approach</em> and the <em>Fisher's approach</em>.</p>
<p>Suppose we have the data $(x,y)$, where $x$ is the $p$-dimensional predictor and $y$ is the dependent variable of $K$ classes.</p>
<p>By <em>Bayesian approach</em>, we compute the posterior $$p(y_k|x)=\frac{p(x... | g59307 | [
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-0.015452099964022636,
0.026424476876854897,
0.06550224870443344,
0.04417360946536064,
0.051... |
<p>I can see an advantage for rating in that you potentially end up with interval data rather than ordinal data. However, I'm struggling to think of what potential advantages there might be to rank-ordering.</p> | g59308 | [
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0.04604380205273628,
0.03872581571340561,
0.026981467381119728,
... |
<p>I am trying to calculate the sample size for a new study based on a previous one.
The previous study compared means using a <em>t</em> test. </p>
<p><strong>I have:</strong> the means, the <em>t</em> test result, the confidence interval of the mean difference, and the effect size. </p>
<p>However, <a href="http://... | g59309 | [
0.004153398796916008,
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0.021089088171720505,
0.0037195924669504166,
0.04460081458091736,
-0... |
<p>I just watched this video: <a href="https://www.youtube.com/watch?v=Fk02TW6reiA" rel="nofollow">https://www.youtube.com/watch?v=Fk02TW6reiA</a></p>
<p>It shows a formula to calculate an answer for the following problem:</p>
<ul>
<li>There are 2 customers expected every 3 minutes in a store</li>
<li>Therefore there... | g59310 | [
0.0006063215550966561,
0.03318799287080765,
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... |
<p>Do you know of an approach/package that facilitates mixed model regression of ordinal dependent variables on multiply imputed datasets in R?</p>
<p>Ideally, the function takes:</p>
<p>a list of multiply imputed datasets</p>
<p>a list of target variables (dependent variables, one or more)</p>
<p>a list of factors... | g59311 | [
-0.007264891639351845,
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0.010150873102247715,
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0.03371254354715347,
... |
<p>I'm currently trying to write a Level 1 model for the following research question.</p>
<p>RQ: Does the school-level relationship between race and the proportion of reading proficient students (outcome) vary by the urbanicity of the school?</p>
<p>RACE is grouped into 7 categories and URBAN is grouped into 3 catego... | g59312 | [
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0.03207376226782799,
0.03192397952079773,
0.03494470193982124,
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0.0334... |
<p>I need your help interpreting my model's results. To make story short, I have a continuous dependent variable $Y$, and two factors $A$ and $B$, each with $2$ levels $(A_1, A_2, B_1, B_2)$. My main interest is the differences between $A_1$ and $A_2$, however I am taking into account the affect of $B$. The observation... | g59313 | [
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0.05019047111272812,
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0.0... |
<p>There is an image in page 204, chapter 4 of "pattern recognition and machine learning" by Bishop where I don't understand why the Least square solution gives poor results here:</p>
<p><img src="http://i.stack.imgur.com/fHyoq.png" alt="enter image description here"></p>
<p>The previous paragraph was about the fact ... | g14776 | [
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0.012209335342049599,
0.027799932286143303,
0.0757737010717392,
0.02... |
<p>My research model has two levels of dependent variable, at the organizational level and a predictor variable at individual level. I have 500 answers from 5 middle managers (in each firm) in 100 firms at an individual level and 200 from 2 top managers (in each firm) from the same 100 firms. </p>
<p>My question is wh... | g59314 | [
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0.029106391593813896,
0.0117322187870740... |
<p>I have a statistical problem in connection to interaction effects and main effects in the social sciences.</p>
<p>I am doing a regression where I have two interaction terms with one common variable. The interaction terms are used in order to prove or falsify two hypotheses. If I include all main effects and interac... | g59315 | [
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0.05614326894283295,
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... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/43529/reducing-no-of-variables-subsetted-based-on-depth-for-pca">Reducing no of variables subsetted based on depth for PCA</a> </p>
</blockquote>
<p>I have a question, I am trying to apply a method to my r... | g49551 | [
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0.005502176471054554,
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0.019479433074593544,
0.03760213404893875,
0.07041750848293304,
0.04... |
<p>In my research, I am trying to show the relationship between an IV and a DV. </p>
<p>As I compute the Pearson correlation through SPSS, it outputs a correlation matrix. This is not what I want. I need an $r$ and a $p$ value only.</p> | g59316 | [
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0.029113948345184326,
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<p>I have several query frequencies, and I need to estimate the coefficient of Zipf's law. These are the top frequencies: </p>
<pre><code>26486
12053
5052
3033
2536
2391
1444
1220
1152
1039
</code></pre> | g59317 | [
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<p>I receive 1000 <em>points</em> per day from installations who produces electricity.
Every installation must proportionally produce the same amount of energy.</p>
<p>I have to spot failures in those data. The actual method : <br/>
1. I make an average. <br/>
2. I make a second average where I remove the installatio... | g14782 | [
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0.... |
<p>I've identified a Single Nucleotide Polymorphism (SNP) that is associated with a variable of interest (lets just call it height) using a Genome Wide Association Study (GWAS). The SNP can be of the values A/A, A/G or G/G in each of the 69 samples.</p>
<p>I also have gene expression data for the 69 samples and it app... | g414 | [
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... |
<p>I have a large number of time series which consist of pricing data of consumer goods. As expected the prices show trend and seasonality. However my main problem is to detect large level changes in the price series. In these data sets this has occurred mainly due to the price being recorded for the wrong packaging si... | g59318 | [
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<p>I came to a situation where the weights of my Neural Network are not converging even after 500 iterations. My neural network contains 1 Input layer, 1 Hidden layer and 1 Output Layer. They are around 230 nodes in the input layer, 9 nodes in the hidden layer and 1 output node in the output layer. I wanted to know, if... | g59319 | [
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<p>The lasso and ridge regression are tuned to the same alpha parameter. No matter what I tune the parameter to [0,1], the results of all three regressions are always the same (linear, ridge, lasso), which is a bit befuddling because I had previously suspected that there was some multicollinearity in my data due to hig... | g27648 | [
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0... |
<p>I was reading this tutorial related to EM algorithm at <a href="http://aass.oru.se/~tdt/ml/extra-readings/EM_algorithm.pdf" rel="nofollow">http://aass.oru.se/~tdt/ml/extra-readings/EM_algorithm.pdf</a>. As given in the tutorial</p>
<p><img src="http://i.stack.imgur.com/v5bqe.png" alt="enter image description here">... | g59320 | [
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0.050581254065036774,
-0.00... |
<p>Suppose I have model 1: $$Y=aX$$ where $X$ is $n\times1$, consisting of a single feature. suppose I fit this model with $L_2$ penalty with coefficient $\lambda=1$ : $$ \underset{a}{\min} \sum_{i=1}^{n}(y_i-ax_i)^2 +a^2$$ and I find that $a=b$.</p>
<p>Now consider model 2 : $Y=a'X'+a''X''$ where $X',X''$ are just du... | g59321 | [
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0.0... |
<p>I've recently installed Apache Commons Math library to help me with some basic statistics in my project.</p>
<p>Basically, what I need is to calculate the correlation coefficient for 2 arrays, which I can do using the class "PearsonsCorrelation".
However, I realized that I should be using a special variant of Pears... | g59322 | [
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<p>Can anyone help me in understanding what kind of noise is it?
Noise = Normal(0, v)
v = GammaFromShapeAndRate(alpha, beta)</p>
<p>I mean what is the advantage of making a normal noise with a Gamma distribution?
And if it shows any specific kind of noise, then how should I determine alpha and beta?
should I set them... | g59323 | [
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<p>I am trying to learn CRF from the unaligned data in Natural Language Understanding application. There is one paper in this field which does exactly the same, <a href="http://cse.seu.edu.cn/people/zhoudeyu/Publications_files/ECIR2011.pdf" rel="nofollow">Learning conditional random fields from unaligned data for natur... | g59324 | [
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<p>I am interested in the identifiability of linear mixed effects models. Let's assume $p$ subject are observed at different instants in time. Let $\mathbf{y}_{i}$ $(1 \leq i \leq p)$ the vector containing the $n_{i}$ observations of the $i$-th subject. We assume the following model :</p>
<p>$$ \mathbf{y}_{i} = \mathb... | g59325 | [
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0... |
<p>I have a mixed/random effects model $$\mathbf{y}_i=\mathbf{X}_i\boldsymbol\beta+\mathbf{Z}_i\mathbf b_i+\boldsymbol\epsilon_i,$$
where random effects $\mathbf b_i$ has variance-covariance matrix $$D=\text{cov}(\mathbf b_i)=\left(\begin{array}{cc}
\sigma_{1}^{2} & \sigma_{12}\\
\sigma_{12} & \sigma_{2}^{2}
\... | g59326 | [
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<p>I was asked by a non-statistician what is the driving factor for the standard error estimates of the parameters. Here are my thoughts:</p>
<ol>
<li><p>From asymptotic theory, both OLS standard error and Quantile regression standard error depends on the error/residual distribution. The OLS standard error mainly depe... | g14796 | [
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<p>Can you see any S-curve in the below scatter plot?</p>
<p>If there is the S-curve is it correct to use a scatterplot plot? If the linear correlation is 0.85, does it mean the S-curve is unlikely?</p>
<p>I am trying to understand the relationship between the two variables.</p>
<p><img src="http://i.stack.imgur.com... | g38422 | [
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<p>I have data that looks a little something like this:</p>
<pre><code>ID Status
01 A
02 G
03 E
... ...
100 G
</code></pre>
<p>You get the idea, I think. I have this data from two separate populations (cohorts) and I want to compare the distribution of the status variable... | g59327 | [
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<p>Given survey data where respondents rated 10 different questions on a scale from 1-10, and whether or not they purchased (binary variable): We are trying to determine which of the survey questions are most strongly correlated to the person's purchasing behavior by calculating a probability or an odds ratio value pe... | g59328 | [
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<p>In the text book <em>"New Comprehensive Mathematics for O Level"</em> by Greer (1983), I see averaged deviation calculated like this:</p>
<blockquote>
<p>Sum up absolute differences between single values and the mean. Then
get its average. Througout the chapter the term <strong>mean deviation</strong> is
used... | g59329 | [
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<p>I'd like to know ahead of time if my training will take 8 hours, 8 days or 8 weeks. (The 8 was an arbitrary number I chose obviously).</p>
<p>Is there a reliable way to estimate the time it will take? Can I extrapolate the time it takes to train 200,000 as roughly double the time it takes to train 100,000? </p>
<p... | g59330 | [
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... |
<p>I'm working with the Emotiv EEG headset. My goal is to collect the signal from its 14 sensors while a subject who is wearing it performs a certain task, and use a machine learning model (a neural network in the present case) to identify certain patterns of interest in the signal from the device.</p>
<p>I would like... | g452 | [
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... |
<p>IN convex optimization : min f(x), I have two constraits : one is sum_i|x_i| <= t (t can be any numbers) , another constraints is |x_j|=|x_j-1 k_j|(set k_1 can not equal to zero and k_j can be thought as instrumental variable).</p>
<p>As we know , if we do not have the second constraint , the models can be solv... | g59331 | [
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0.007... |
<p>Suppose I have two groups and several dependant variables. I would like to show statistically whether the two groups are different or not, based on the combination of these dependant variables. The dependant variables will be correlated to some extent.</p>
<p>When doing t-test or ANOVA each of my dependant variable... | g59332 | [
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... |
<p>In the article "Discussion: Should Ecologists Become Bayesians?" Brian Dennis gives a surprisingly balanced and positive view of Bayesian statistics when his aim seems to be to warn people about it. However, in one paragraph, without any citations or justifications, he says:</p>
<blockquote>
<p>Bayesians, you see... | g59333 | [
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0.01... |
<p>I want to find the expected number of coin tosses to get $N$ heads in a row, where $p$ is the probability of getting a head in a single toss. </p>
<p>Let $F(N)$ be the expected number of tosses to get $N$ heads consecutively, so </p>
<p>$$F(N) = 1 + p F(N-1) + (1-p) F(N)$$ </p>
<p>which gives </p>
<p>$$F(N) = ... | g59334 | [
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<p>How do you perform hypothesis tests with big data? I wrote the following MATLAB script to emphasize my confusion. All it does is generate two random series, and run a simple linear regression of one variable on the other. It performs this regression several times using different random values and reports averages. W... | g59335 | [
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0.01... |
<p>Bootstrapping approach is based on the assumption that the sample is the population. Then, a resampling of the sample is done, replacing the individuals of the population by chance. The number of the resampled individuals is the same as the 'real' sample. So, how is the new sample different from the original one?
I ... | g59336 | [
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0.05232734605669975,
-... |
<p>My response variable is a questionnaire score ranging <strong>from 1 to 5</strong> (which can take intermediate values like 1.3, 4.7, etc.). However, when the plot is made, I can see the density line <strong>reaching values under 1 and over 5</strong>, something like: </p>
<p><img src="http://i.stack.imgur.com/CtGr... | g59337 | [
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0.021811220794916153,
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0.0... |
<p>I am using different Likert Scales in questionnaire. Three dependent variables have Likert scales of 4 points, 2 points and 2 points. Three independent variables have 3 points scales. One moderating variable has 3 points Likert Scale whereas the other moderating variable has three questions with 4 points, 3 points a... | g49552 | [
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... |
<p>I failed to pass my regression analysis course as the lecturer didn't say what kind of analysis he wants on the data. The problem was:</p>
<blockquote>
<p>The index of biotic integrity (IBI) is a measure of the water quality in streams. IBI and land-use measures for a collection of streams in the Ozark Highland e... | g59338 | [
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0.0... |
<p>I was not able to find this question here, so I am going to ask this:</p>
<ul>
<li><p>What is the difference between $\mathbb{E}(\bar{X})$ (expected value of $X$ bar) and the actual $\bar{X}$?
I am very confused about these two concepts. How come $\bar{X}$ is one of the estimators of normal distribution (the other ... | g59339 | [
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0.017084190621972084,
-... |
<p>I want to calculate the AIC without calculating the loglikelihood-function (which seems complicated). If the residuals are normally distributed, this can be done, according to wikipedia, as follows:</p>
<p>$AIC_{\sigma} = n log(\sigma^2_Z) + 2k $,</p>
<p>where $\sigma^2_Z$ is the variance of the residuals, $n$ the... | g59340 | [
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0.0... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/32706/existence-of-the-moment-generating-function-and-variance">Existence of the moment generating function and variance</a> </p>
</blockquote>
<p>Given that there is an interval $-h < t < h$ where M... | g49553 | [
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<p>I got a dataset, there are about 400 variables, most of the variables are quite similar. Actually, I would like to say their number are pretty close, but I think they won't too correlated, since the graph for the variables is like a heart beat monitor. But just at some point it varies too much.
<img src="http://i.st... | g59341 | [
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0.0... |
<p>I'd like to know the correct way to simulate test data for a simulation study. For simplicity, suppose that I want to test a linear regression model. Chapter 7 of <a href="http://statweb.stanford.edu/~tibs/ElemStatLearn/" rel="nofollow">ESL</a> explains that the average test error is equal to the expected prediction... | g59342 | [
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0.01134098693728447,
0.05658451467752457,
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... |
<p>In text categorization, it is common to use tokens as features. But, there are several different ways to convert a sentence to tokens. For example, see the different types of Tokenizers here: <a href="https://github.com/NaturalNode/natural" rel="nofollow">https://github.com/NaturalNode/natural</a> . What is the most... | g59343 | [
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0.03... |
<p>This is a follow-up question on that one:<br> <a href="http://stats.stackexchange.com/questions/70086/could-bessels-correction-make-sample-variance-estimation-even-more-biased">Could Bessel's correction make sample variance estimation even more biased?</a></p>
<p>I understand that you need Bessel's correction t... | g59344 | [
0.06335154920816422,
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0.01605835184454918,
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-0.0004885123926214874,
-0.006361328065395355,
0.006299832370132208,
0.018489941954612732,
0.029844846576452255,
0.05393243581056595,
0.03007754310965538,
0.014902105554938316,
-0.04402719810605049,
0.022... |
<p>I have to classify data between N classes.</p>
<p>At the first step, I make a classification between N classes with low threshold (for example, 10%). When first step is over, I have $M$ labels assigned to my datum $(M \leqslant N)$.</p>
<p>At the second step, I make normal classification with normal threshold betw... | g14825 | [
0.025939421728253365,
-0.005190328229218721,
-0.02591625414788723,
-0.03376292064785957,
0.014532392844557762,
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0.01861184649169445,
0.038017868995666504,
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-0.015262685716152191,
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0.041987378150224686,
0.06431928277015686,
-0.... |
<p>I have a bunch of groups of DNA sequences in which I have observed changes in different regions (block D and H) vs. the rest of the molecule. The data is available as a table like the one below. The first row means the total number of changes in cluster 1 were 4, 0 in block D and 0 in block H, meaning they were fou... | g14826 | [
-0.007164804730564356,
-0.022666892036795616,
-0.0071671041660010815,
-0.05112506076693535,
-0.004103967919945717,
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0.018463721498847008,
0.03821871057152748,
-0.0033127868082374334,
-0.021769041195511818,
-0.008821041323244572,
0.041913118213415146,
0.01754453405737877,... |
<p>Let $B(n,p,r)$ denote the binomial distribution function (DF) with parameters $n \in \mathbb N$ and $p \in (0,1)$ evaluated at $r \in \{0,1,\ldots,n\}$:
\begin{equation}
B(n,p,r) = \sum_{i=0}^r \binom{n}{i} p^i (1-p)^{n-i},
\end{equation}
and let $F(\nu,r)$ denote the Poisson DF with parameter $a \in \mathbb R^+$ ev... | g459 | [
-0.0010232317727059126,
-0.01207889523357153,
0.0040064346976578236,
0.01096143014729023,
0.014780747704207897,
-0.01839391700923443,
0.020896360278129578,
-0.030111178755760193,
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-0.02862931787967682,
-0.07472220063209534,
0.05314793437719345,
-0.06450257450342178,
-0... |
<p>I have a data frame that contains two time series: the dates and version numbers of Emacs and Firefox releases. Using one ggplot2 command it's easy to make a chart that uses loess (in a way that looks a bit amusing, which I don't mind) to turn the points into lines.</p>
<p>How can I extend the lines into the future... | g59345 | [
0.006124975625425577,
-0.0022185074631124735,
0.016824031248688698,
-0.07326958328485489,
0.004421185236424208,
-0.014446930028498173,
0.01770194247364998,
0.001962479203939438,
-0.057528305798769,
-0.05872563272714615,
0.0248012263327837,
0.0444544181227684,
0.10044719278812408,
0.0541250... |
<p>I'm working on something like the following problem. I have a bunch of users and N books. Each user creates an ordered ranking of all the books he's read (which is likely a subset of the N books), e.g., Book 1 > Book 40 > Book 25.</p>
<p>Now I want to turn these individual user rankings into a single ordered rankin... | g59346 | [
-0.06390196830034256,
0.01359635777771473,
-0.01960171014070511,
-0.04349368438124657,
-0.008213624358177185,
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-0.014505298808217049,
0.03043455258011818,
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0.04840044304728508,
0.041646283119916916,
-0.06831134855747223,
0.044443279504776,
-0.0090... |
<p>I need to compare the goodness of fit of several averaged logistic regression models by calculating the deviance explained. I'm using the <code>MuMIn</code> package in R to average many logistic regression models into a single averaged model. I ultimately want to compare the explanatory power of several averaged mod... | g500 | [
0.005657033994793892,
-0.056138429790735245,
-0.0031063794158399105,
-0.03385200724005699,
0.04113509878516197,
-0.06835184246301651,
0.007962712086737156,
0.05706571787595749,
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-0.027441367506980896,
-0.05332285538315773,
-0.014820856973528862,
0.0497092679142952,
0... |
<p>I am trying to fit a linear model to my data, which consist of a continuous dependent variable and several predictors, some continuous, some discrete and one dummy. </p>
<p>I used the R package glmnet, and the best R squared that I get is of 0.5. </p>
<p>Is there something that I could try to improve the model? Pe... | g59347 | [
0.030852938070893288,
-0.04285218194127083,
-0.014322678558528423,
-0.046076398342847824,
-0.027010846883058548,
-0.010333075188100338,
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-0.08102644979953766,
-0.029048575088381767,
0.035526808351278305,
-0.0022893843706697226,
0.01960843987762928... |
<p>I'm trying to figure out how SPSS is initializing the multiplicative Holt Winters exponential smoothing model using backcasting. Thankfully IBM roughly <a href="http://pic.dhe.ibm.com/infocenter/spssstat/v21r0m0/topic/com.ibm.spss.statistics.help/alg_tsmodel_models_exsmooth_estimation_initialization.htm" rel="nofoll... | g59348 | [
0.011379609815776348,
-0.04251537472009659,
-0.022109592333436012,
0.0031746800523251295,
-0.010773283429443836,
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0.048586178570985794,
0.04472152143716812,
-0.03541131690144539,
0.01229318231344223,
-0.01896398887038231,
0.0917392447590828,
0.08504874259233475,
0.020... |
<p>Good day everyone, I am currently working on a self-study question:</p>
<p><strong>Question</strong></p>
<blockquote>
<p>The number of viewers of a television show has a mean of 29 million with a standard deviation of 5 million. Assume this distribution follows a normal distribution. What is the probability that... | g59349 | [
-0.014243688434362411,
0.08065558224916458,
0.009248093701899052,
-0.01376236230134964,
-0.04765884578227997,
-0.014699088409543037,
0.005539293400943279,
-0.002871857490390539,
-0.001960219582542777,
-0.02866404876112938,
-0.0394895076751709,
0.017459791153669357,
0.015470370650291443,
0.... |
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