question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p><a href="https://www.seas.harvard.edu/courses/cs281/papers/unscented.pdf" rel="nofollow">Parameter estimation of nonlinear systems unscented kalman filter</a> ( paper and many others are categorized under semi-blind identification technique because the Authors say that the dynamics of the nonlinear map i.e the syst... | g60776 | [
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<p>I am working in R with daily time series data and have daily observations of two variables. The first is continuous. The second is zero for every day except one, in which it is a number (<em>I'm not sure what to call it, so I referred to it as “almost-Boolean” in my title</em>). Both variables are stationary. I h... | g60777 | [
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<p>I am wondering how to test for differences in regression coefficients across groups <strong>in panel data</strong> (after a fixed-effects regression).</p>
<p>Particularly, I can't think of a solution of how to construct interaction terms if the groups you are interested in are <strong>not</strong> the same than the... | g60778 | [
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<p>I have a complex experimental design: 3 groups, each of which come on 4 occassions and I obtain recordings from 250 skin electrodes. I am interested in knowing which of the electrodes provides a useful indicator for predicting the group x occassion interaction. So, if I do 250 ANOVAs (3x4), surely I will need to cor... | g60779 | [
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<p>could you please provide an example or give a relevant formula
for the following situation:
correlation between variables (x and y) is excellent,
but the prediction of y by x values is poor,
when using a linear regression model.</p>
<p>Thank you very much!</p> | g60780 | [
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<p>I frequently use this model to test catch efficiency and size selection properties of a given trawl fishing gear:</p>
<p>\begin{equation}
\theta(l)=\frac{s\times r(l)}{(1-s)+s\times r(l)}
\end{equation}</p>
<p>where $\theta(l)$ denotes the expected catch rate in the test gear ($T$), which has been fishing in paral... | g15769 | [
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<p>I'm essentially learning about Latent Dirichlet Allocation. I'm watching a video here: <a href="http://videolectures.net/mlss09uk_blei_tm/" rel="nofollow">http://videolectures.net/mlss09uk_blei_tm/</a> and stuck at minute 45 when he started to explain on sampling from the distribution.</p>
<p>Also I tried to consul... | g60781 | [
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<p>I have a distribution that is skewed to the left (i.e. a lot of low values, aka positive skew - verified)</p>
<p>Basically, I have either a lot of similar low [~minimum] values, or 0 values, or something like 1 value that is the only value below the median value.</p>
<p>The data has already been normalized to 0 to... | g60782 | [
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<p>I have data which is showing a $p$-value of $0.15$ significance value within a MANOVA (including a significant planned contrast). However, when I dummy code and put it into an OLS regression, the result is significant.</p>
<p>Any ideas on what to do? Should I just report the MANOVA being non-significant however hav... | g60783 | [
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<p>I want to extend the standard <a href="http://en.wikipedia.org/wiki/Error_correction_model" rel="nofollow">VECM</a> form:</p>
<pre>
Δx[t] = δ0 + ... + Π x[t-1] + Φ1 Δx[t-1] + Φ1 Δx[t-2] + ... + ε
</pre>
<p>to include exogenous variables (i.e. variables that are participant in describing the relationships amongst <... | g46659 | [
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<p>Maybe it's a basic question, but I'm learning about GLMM using the lme4 package. I'm confused about the way that I can know the significance the overall model using glmer.</p>
<p>First, the random model is:</p>
<pre><code>fit.random <- glmer(VDEP ~ AGE +GENDER +EDUC +V1 +V2 +V3 +(1|STATE), family = binomial("lo... | g60784 | [
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<p>This may be a naive question, but here goes. If I have a set of empirical data and fit a kernel density to it, and then obtain a new single value which possibly comes from the same process which generated the original data set, can I assign a probability that this new value belongs to the set/process by simply readi... | g17047 | [
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<p>For $Y \sim \mathcal{N}(\mu,\sigma^2)$,</p>
<p>$$X = \frac{\exp(Y)}{1+\exp(Y)},$$</p>
<p>so $X$ has a logit-normal distribution. Then</p>
<p>$$\mathbb{E}(X^2) = \int_{-\infty}^\infty \frac{\exp(2y)}{\left(1+\exp(y)\right)^2}\frac{1}{\sqrt{2\pi}\sigma}\exp{\left(-\frac{(y-\mu)^2}{2\sigma^2}\right)} dy $$</p>
<p>C... | g60785 | [
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<p>I would like to select features for a support vector regression for forecasting. I would like to forecast a value at point t with the values t-1,...t-x as features. Now I want to select the most important features which leads to a good forecast. I tried to calculate the mutual information (MI) between the value and ... | g60786 | [
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... |
<p>Can you nominate which are the steps which I need to follow in order to get a basic grasp into the field of forecasting? which are the "must to know things"? </p> | g49599 | [
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<p>I am interested in the expectation and the variance of the maximum of several independent, normal distributed variances. That is, given a set of $I$ different RVs with $X_i \sim \mathcal{N}(\mu_i, \sigma_i^2)$, I want to find
$$
\mathbb{E}[\max~X_i], \\
\text{Var}[\max~X_i].
$$</p>
<p>I have found Ross' "Compu... | g60787 | [
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<p>i want to classify persons using their electrical consumption data, imagine the following data set:</p>
<p><img src="http://i.stack.imgur.com/YuDDd.jpg" alt="enter image description here"></p>
<p>"result" is the class variable that I want to detect by using the mean and max Consumptions.</p>
<p>I am sure that it ... | g17050 | [
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<p>I'm a beginner at hierarchical modeling and statistics in general and this is confusing me. </p>
<p><strong>Question:</strong> If I draw a histogram of a posterior distribution from an MCMC chain, do I draw the prior as a histogram, too, or do I just <em>paste</em> the distribution into the posterior plot (and make... | g60788 | [
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<p><strong>Context:</strong> I am working on a calibration problem involving a 1D function of parameter $\theta$ for which I derived a Jeffreys prior (in fact a 2D but I have an informative prior for one of the parameters).</p>
<p><strong>Observation:</strong> Using this prior gives me in practice very bad inference r... | g60789 | [
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<p>For my thesis I computed various rejection frequencies based on p-values using various statistics based on the Wild Restricted Efficient bootstrap scheme of Davidson & Mackinnon (2010) by simulation, which I replicated in Matlab. The following to pictures show the size and power of the statistics respectively un... | g60790 | [
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<p>I would like to derive the likelihood function corresponding to a student t model as a mixture of distribution, but there is one point which is not completely clear to me.</p>
<p>It is usually written that $X=\mu+\frac{1}{\sqrt{\frac{U}{\nu}}}Y$ is a student t distributed variables if U is distributed as a $\chi^{... | g60791 | [
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<p>Many statisticians have observed that the significance of an interaction term is crucially dependent on there being a linear relationship between construct and observed trait (e.g. papers by Bogartz, 1976, and Loftus, 1978, at foot of posting). Salthouse (2000; 149) also provides an excellent visual demonstration of... | g15773 | [
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<p>Hi i'm developing an hidden markov model algorithm training with multiple sequences. The recognition rate is good but i have doubts about the shape of the curve of log likelihood obtained from the iteration of baumwelch. Here you have two example, i'm doing it wrong?!Shouldn't be always concave? xaxes=iteration, yax... | g17053 | [
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<p><a href="http://www.real-statistics.com/statistics-tables/shapiro-wilk-table/" rel="nofollow">http://www.real-statistics.com/statistics-tables/shapiro-wilk-table/</a></p>
<p>I am trying to build a function that performs a Shapiro-Wilk test on a sample population, but I cannot figure out how the a-values in the Shap... | g60792 | [
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<p>Let $X$ follow a uniform distribution and $Y$ follow a normal distribution. What can be said about $\frac X Y$? Is there a distribution for it?</p>
<p>I found the ratio of two normals with mean zero is Cauchy.</p> | g60793 | [
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<p>My data looks like this:</p>
<pre><code>Color | X_1 X_2 ... X_n
-----------------------
red | 0.5 0.9 ... 0.2
green | 0.7 0.7 ... 0.3
red | 0.8 0.3 ... 0.2
blue | 0.7 0.4 ... 0.2
...
</code></pre>
<p>I want to test for a correlation between the categorical variable Color and each interval variable X_i. What i... | g49600 | [
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<p>It would be appreciated if the following examples could be given:</p>
<ol>
<li>A distribution with infinite mean and infinite variance.</li>
<li>A distribution with infinite mean and finite variance.</li>
<li>A distribution with finite mean and infinite variance. </li>
<li>A distribution with finite mean and finite... | g17056 | [
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<p>my apologies for my poor knowledge on statistics. Is there a way to calculate the prediction interval at 95% confidence level of a perfect-fit model? I want to compare how my actual model prediction compares with the perfect-fit model. I want to see if the predicted points fall within the 95% prediction interval of ... | g60794 | [
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<p>Assuming I can download from facebook a list of my friends, and which of them are friends with each other - can I estimate from this information which of them is "central"? (I am not exactly sure how to define what "central" is in this context)</p>
<p>What information/assumptions are needed?</p>
<p>Thanks.</p> | g60795 | [
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<p>I'm currently dealing with large DNA sequences for machine learning purposes, I'm basically improving existing methods.</p>
<p>What I have is several millions of DNA sequences :
ACGTAGGCAGGCTTTC ... </p>
<p>In the methods I'm currently reviewing they extracts the features like this :
for every nucleobase they put... | g17057 | [
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<p>In consecutive throws of an ordinary dice, which of the following two possibilities is more likely to happen first: </p>
<p>a) Two successive occurrences of 5 or</p>
<p>b) Three successive appearances of numbers divisible by 3?</p>
<p>I thought that "time to event" random variable follows a geometric distribution... | g24837 | [
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0.04748499393463135,
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0.005361753050237894,
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0.06107470393180847,
0.04229278117418289,
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<p>I am dealing with data with unbalanced sample size (12k vs 18k) and variance(0.2 vs 0.4) and want to perform a two sample t-test. With the unbalance features, I am thinking apply bootstrap t-test. Can I just re-sample from the larger data-set and perform t-test many times then get the average?</p>
<p>Thanks for all... | g17061 | [
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0.01410245057195425,
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0.009549954906105995,
0.0207... |
<p>I need to compare a multidimensional pain scale item response >3 pain is present and a scale measuring emotional suffering with classified levels of suffering (High, intermediate and low). Will ICC help?</p> | g60796 | [
0.005594578571617603,
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<p>I have <code>546,255</code> edges between set <em>X</em> and set <em>Y</em>. </p>
<p>I need to calculate the recall and precision values for these <code>546,255</code> edges. However, after some research, I found that calculating recall for such a large number is nearly impossible. Instead, the measure that can be ... | g17062 | [
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<p>I am curious if any research has been conducted to efficiently combine trees resulting from a gradient boosting process. I routinely run a process that generates 20 or 30 thousand trees in R. I then convert these trees to SAS which results in hundreds of thousands of lines of code. Many of the trees are very similar... | g60797 | [
0.007496874779462814,
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0.02874308079481125,
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0.034511540085077286,
0.05905357375741005,
0.042... |
<p>Thank you in advance for any and all help. This problem is for an MBA class. I'd like to use R as a new tool that I haven't worked with before. I have some experience working with data, but primarily for business analysis and not in-depth statistical analysis. </p>
<p><strong>Background</strong>
The problem is ... | g60798 | [
-0.02561245858669281,
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0.0241991113871336,
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0.017852703109383583,
... |
<p>I have been lurking here for awhile and now have a question I hope to get answered! </p>
<p>I am wondering how to get nearest neighbor algorithms to deal with NAs most effectively. I am dealing with a data set where I would like something like </p>
<p>(10,10,NA,NA)</p>
<p>would still be a nearest neighbor with</p... | g60799 | [
0.048545558005571365,
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0.005497592967003584,
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0.029855886474251747,
0.0501173734664917,
0.024759329855442047,
0.047... |
<p>I'm looking for a technique that would help me rank individuals according to 3 scores A, B and C (each representing a separate score in 3 specific fields).</p>
<p>A, B and C are all normalized value between 0 and 1, where 0 is the worst possible score, and 1 is the best possible score. I could simply average the th... | g60800 | [
0.0196980070322752,
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<p>I'm using R to fit a neural network to data generated by the formula $y = x^2 + \epsilon / 2$ where $x \sim \mathcal{U}(0, 2)$ and $\epsilon \sim N(0, 1)$ (very simple, right?). The following plot shows the plot of function $x^2$ and the generated data:
<img src="http://i.imgur.com/DDnbIxA.png" alt="1"></p>
<p>Now,... | g9658 | [
0.005259741563349962,
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0.011274345219135284,
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0.009715230204164982,
0.040935859084129333,
0.019032176584005356,
... |
<p>I have the same problem as the following post, but I have more samples and the index of the outlier is known. </p>
<p><a href="http://stats.stackexchange.com/questions/73304/outlier-treatment-in-vector-autoregression-var-model?newreg=31eda9f1618047dcba346fdcb8014dcb">Outlier treatment in Vector Autoregression (VAR)... | g60801 | [
0.02478860504925251,
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0.006661515682935715,
0.09752678126096725,
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0.0... |
<p>I have a ratio of two random, (dependent or independent) normally distributed variables.</p>
<p>Knowing that the resulting Cauchy-distribution does not produce any moments. May I ask: Is there an approximation to a Cauchy distribution? Can I still get something out of my set of ratios? </p> | g830 | [
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0.022463791072368622,
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-0.02097611129283905... |
<p>I have a set of desired properties and I would like to find a distribution family that satisfies these properties.</p>
<ol>
<li>The distributions in the family are continuous and supported on bounded intervals. They are finite at all points of their bounded supports, normalizable, and have finite mean and variance.... | g60802 | [
0.015601364895701408,
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0.00012630742276087403,
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... |
<p>I am looking at using a <a href="http://en.wikipedia.org/wiki/Fractional_factorial_design" rel="nofollow">fractional factorial</a> design in order to reduce the number of treatment runs for an experiment involving a binary outcome. The <a href="http://support.sas.com/resources/papers/proceedings12/206-2012.pdf" rel=... | g60803 | [
0.024348890408873558,
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0.00678280321881175,
0.05929632857441902,
0.04086899012327194,
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<p>As is known to all, SVM can use kernel method to project data points in higher spaces so that points can be separated by a linear space.
But we can also use logistic regression to choose this boundary in the kernel space, so what's the advantages of SVM?
Since SVM uses a sparse model in which only those support vec... | g60804 | [
0.05050206184387207,
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0.06035042181611061,
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0.029975097626447678,
0.004799709189683199,
0.06431586295366287,
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<p>I have some psychological data (N=100, 2 conditions) in which across 55 questions participants made an estimate, and then after a manipulation they made an additional estimate. I then calculated how much their estimate gained or lost on the second round. There were two manipulations that occurred before the second r... | g17071 | [
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0.030465018004179,
0.034273743629455566,
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0.020279303193092346,
0.00... |
<p>I am studying the ARMA models, and I am breaking my head on something probably straightforward but that I can't see.</p>
<p>I generated in R a simple AR(1) model, and used the function ARIMA to estimate its coefficients. I get two coefficients, an AR(1) coefficient and an intercept.</p>
<p>Now I am trying to calcu... | g17078 | [
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0.019034389406442642,
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0.04428303241729736,
0.10208626091480255,
0.021... |
<p>I have two sets of random variables. I have generated two CDFs for them. Two of the CDFs are plotted graphically.<img src="http://i.stack.imgur.com/oetZL.png" alt="enter image description here"> I need to find the difference in distribution of the two CDFs.
I have learned about the method called convolution of dist... | g17079 | [
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... |
<p>Imagine you have an array of integer numbers. You need to calculate the probability of encountering some integer sub-array in that list. </p>
<p>For example: </p>
<p><strong>the original list:</strong> '1284726437594563495834905834095845634853' which is N integers from 0 to 9.</p>
<p><strong>the question is:</str... | g49601 | [
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0.029609860852360725,
0.0026654789689928293,
0.056988801807165146,
0.003093272913247347,
0... |
<p>I run a series of models using GAMLSS stepGAIC model selection. The problem that I have is that in GAMLSS, stepGAIC uses AIC values to select the variables in the model. Since my sample size is considered small I probably need to use the AICc values to select the best model. I don’t know if I would be able to create... | g17082 | [
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0.024655591696500778,
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0.00736485980451107,
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0.06571079045534134,
0.... |
<p><a href="http://en.wikipedia.org/wiki/Principal_component_analysis" rel="nofollow">PCA</a> works like this: the first greatest variance on the first principal component, the second greatest variance on the second principal component, and so on.</p>
<p>For me there is a problem with this iterative process.</p>
<p>... | g60805 | [
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0.01181512139737606,
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0.08879006654024124,
0.04811493679881096,
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0.0... |
<p>I was reading a research paper:</p>
<p>$Y_{t}\text{=}\beta_{0}+\beta_{1}X_{1t}+\beta_{2}X_{2t}$
(where $Y_{t}$ is stock returns and not the change in stock returns)
($X{}_{1t}$ is the return of a stock market index and $X_{2t}$ is the return of a bond index)
They think $X_{2t}$ follows an AR(3) process and they men... | g12348 | [
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0.027570905163884163,
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0.11065801233053207,
0.05031200125813484,
-... |
<p>Please reference this question (stats.stackexchange.com) <a href="http://bit.ly/got8Bs" rel="nofollow">http://bit.ly/got8Bs</a> for study design and initial reply from caracal.</p>
<p>My question now is: How can I test for an interaction contrast between two groups as (s)he suggested? I'm on the science side of thi... | g46735 | [
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0.06601228564977646,
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<p>I have a question about the AR(1) model. Expressed mathematically as:</p>
<p>$$ Z_{t} = \rho Z_{t-1} + \epsilon_{t}, t=1,..,T$$
$$ \epsilon_{t} \sim iid \ N(0,1) $$</p>
<p>My question is about the "transformation group" method of creating non-informative priors, which I believe initially was suggested by Edwin Ja... | g46738 | [
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0.059028785675764084,
0.016083549708127975,
0.00... |
<p><strong>Motivation</strong>: I'm writing a state estimator in MATLAB (the unscented Kalman filter), which calls for the update of the (upper-triangular) square-root of a covariance matrix $S$ at every iteration (that is, for a covariance matrix $P$, it is true that $P=SS^{T}$). In order for me to perform the requisi... | g46739 | [
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0.0170317143201828,
0.03649156168103218,
0.014831505715847015,
0.07329414039850235,
0.04... |
<p>I learned about the zero-inflated negative binomial distribution a few months ago when I was trying to do regression on some discrete data. I have a different data set now, and it seems to be very similar except that the value <code>1</code> seems to be over-represented (as opposed to <code>0</code>). Is there such ... | g60806 | [
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0.03160112351179123,
0.006985961459577084,
0.023262476548552513,
... |
<p>I am still confused, despite similar questions being asked, about the difference between the variance and standard deviation in statistics. Why is the variance squared? </p> | g49295 | [
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0.00874925497919321,
0.020278625190258026,
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<p>If I have a list of values throughout time, say a list of values for every minute throughout an hour of monitoring something, can I somehow 'predict' or estimate what the value would probably be in the future, say another 20-30 minute after my last known value? And if so, how can this be done?</p>
<p>I figure mayb... | g17088 | [
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0.05234246328473091,
0... |
<p>First of all I have to mention, that I'm not a statician at all, I'm just a simple programmer and I have some curiosities... and the wrost of all, i don't know where to start from.</p>
<p>Let's assume the following working scenario:</p>
<p>A big company, a internet service provider (ISP) with unlimitd bandwith cho... | g519 | [
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0.00867688748985529,
0.08136814832687378,
0.032... |
<p>When using a binomial family, logit link for GLM (or GEE in my case), I notice that my model estimates diverge when my response variables (which are continuous probabilities with range 0 to 1) include 0 or 1 (or 0 <= y <= 1) as observed values, but the models with response variables that don't include 0 or 1 (... | g60807 | [
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0... |
<p>I'm going to start out by saying this is a homework problem straight out of the book. I have spent a couple hours looking up how to find expected values and have determined I understand nothing.</p>
<blockquote>
<p>Let $X$ have the cdf $F(x) = 1 - x^{-\alpha}, x\ge1$.
Find $E(X)$ for those values of $\alpha$ fo... | g17092 | [
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0.029961908236145973,
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0.03818438947200775,
0.028011199086904526,
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-0.0727149173617363,
-0.03760398551821709,
0.0011385214747861028,
0.03643941506743431,
0.04... |
<p>I run the following scripts in r for mixed effect logistic regression.</p>
<pre><code>textbook.usage.glm <- glmer(textbook.usageSession ~ session.week * condition.player + (1|group.name),family="binomial",data=dfDSP)
summary(textbook.usage.glm)
</code></pre>
<p>And I got the following results.</p>
<pre><code>... | g60808 | [
0.0001594964269315824,
-0.07268035411834717,
0.0014715681318193674,
-0.03654102981090546,
0.003587593324482441,
0.0033216988667845726,
0.077915720641613,
-0.008742733858525753,
-0.04222331568598747,
-0.043789055198431015,
0.036591947078704834,
0.00674486206844449,
0.022884121164679527,
0.0... |
<p>I'm trying to use the FastICA algorithm in MATLAB. My question is: How do I know, which is the optimal number of ICs? I have a matrix of 62 samples with 1009 signals and the FastICA algorithm returns 31 ICs. Why 31? Is there some output where I can see how much variance has been explained by what number of component... | g60809 | [
-0.01754978485405445,
0.019795872271060944,
0.014743435196578503,
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0.013892948627471924,
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0.05779528617858887,
0.016240661963820457,
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0.004197604954242706,
0.04695307835936546,
0.04764223098754883,
-0.0... |
<p>We all know</p>
<p>Leptokurtic ~ Kurtosis > 3 and Platykurtic ~ Kurtosis < 3</p>
<p>I am bit confused about the shape of the curve. Somewhere I had read that since the area under the curve should be 1, for leptokurtic distributions (since the peak is higher than the Normal distribution), the tails approach the ... | g60810 | [
0.05710132420063019,
0.009597324766218662,
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0.012809288688004017,
0.009265553206205368,
0.0017993043875321746,
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-0.02660093829035759,
0.0037854891270399094,
0.03387210890650749,
0.1022852435708046,
-0.0... |
<p>I have the daily closed values of the initial index for DJUSER, MSCI, SP500, SPGSCI from 1 January 1999 to 31 December 2011. I want to transform them in to data of rolling annual returns.</p>
<p>How to do it using R? which package do I need to use?</p>
<p>The density of the rolling annual returns associate to ea... | g60811 | [
0.04769030958414078,
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<p>I need to draw two time-series plots on a graph in <code>R</code>. The problem I am facing is as follows. Each plot has 200 data points, and therefore, the graph that I have produced looks clumsy on my two-column pdf file. I am trying to use different <code>pch</code> values, but still the graph doesn't look good to... | g46751 | [
0.029927680268883705,
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0.025363577529788017,
0.05135590210556984,
0.05526614189147949,
0.031213702633976936,
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<p>I'm using <code>smooth.spline</code> for some basic smoothing splines. However, I need to switch to a function that allows me to use multiple independent variables. I'm having trouble finding one, other than <a href="http://rss.acs.unt.edu/Rdoc/library/mda/html/mars.html" rel="nofollow"><code>mars</code></a>, whic... | g60812 | [
0.026996977627277374,
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0.034022118896245956,
0.015943467617034912,
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0.005... |
<p>I'm trying to run the libsvm-provided wrapper script easy.py on a training set of 100K rows, each row has ~300 features. The feature data is relatively sparse, say only 1/10th are non-zero values.</p>
<p>The script is excruciatingly slow, I'm talking days (or more). I ran the same script on 1% of the data, and it f... | g45406 | [
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0.03537079319357872,
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-0.017222629860043526,
0.03671087697148323,
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0.08932511508464813,
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<p>I am considering a model that includes a covariance matrix which is a function of model's parameters:
$$
\mathbf \Sigma = \Sigma(\mathbf \theta),
$$
where $\mathbf \theta$ is $p$-dimensional, $\mathbf \Sigma$ is $d \times d$ and $d \geq p$.</p>
<p>I know that for every $\mathbf \theta$, $\mathbf \Sigma(\mathbf \the... | g60813 | [
0.05895089730620384,
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0.0062393001280725,
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0.0... |
<p>I have a data set which comprises N measurements. Each measurement is an 8 dimensional vector representing 8 voltages measured from a machine. I want to compute the covariance matrix of this data. Lets assume I have made the data zero mean, hence I want to find $E[V_i*V_j]$ where $V_i$ is the i-th component of a mea... | g17098 | [
-0.004562057089060545,
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0.014771718531847,
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0.07188137620687485,
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-0.0029425304383039474,
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0.018709730356931686,
0.00469288881868124,
0.072... |
<p>When a time series follows an IMA(1,1) process and single exponential smoothing (SES) is used as a forecasting method, should we select a low smoothing constant ($\alpha<0.3$) or a larger one ($\alpha>0.5$)? What is the intuitive interpretation?</p> | g60814 | [
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<p>Suppose you have a series of <em>n</em> trials, where the probability of success
in each trial is <em>p</em>. The distribution of the number of successful trials
follows a Binomial distribution with parameters (n, p). The mean is given
by <em>np</em> whereas the variance is <em>np(1-p)</em>. So far so good: this... | g37716 | [
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-... |
<p>I m working on a piecewise linear growth model and I need help to understand how to write my <code>lmer()</code> code and how to interpret the <code>R</code> output.</p>
<p>My data are the sales return of different IDs over a period of time. I want to know how the sales-return (growth) changes after a certain event... | g60815 | [
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0.03672970086336136,
0.024224013090133667,... |
<p>I have a joint probability distribution as given in the figure:</p>
<p><img src="http://i.stack.imgur.com/jBQN4.png" alt="enter image description here"></p>
<p>In this figure, variables in circles are random variables and variables in squares are constants. So, I can write the joint distribution over the data $y$ ... | g17107 | [
0.038683608174324036,
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0.012557869777083397,
0.024208033457398415,
0.01031648088246584,
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... |
<p>For a stats question the data was not normally distributed but the question required a two way ANOVA, a transformation was therefore used and all worked out fine.</p>
<p>Now the next part requires the data set to be split by one of the nominal variables (in SPSS) and a t-test to be run.</p>
<p>Obviously the transf... | g60816 | [
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0.03528028354048729,
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<p>Under what condition(s) do I need to test for homoscedasticity (i.e. using the Levene's test)? Is this only for repeated-measure designs or do I need to test for this in independent designs as well?</p> | g17108 | [
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<p>This <a href="http://stats.stackexchange.com/questions/31985/definition-and-origin-of-cross-entropy">question</a> gives a quantitative definition of cross entropy,
in terms of it's formula.</p>
<p>I'm looking for a more notional definition,
wikipedia says: </p>
<blockquote>
<p>In information theory, the cross en... | g60817 | [
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0.025257956236600876,
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<p>I was reading a social science paper that tried to explain the correlation between two variables. In that reference there was mention of its standard-error and p-value and that got me to thinking whether the author was using an unknown formula (to me) involving both the explanatory and response variables. My hunch i... | g60818 | [
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... |
<p>I would like to test whether 3 dependent variables (measured with the same participants) differ in variance. My plan is to fit one model in which the 3 variables have the same variance, and one model in which they are allowed to have a different variance, and to then compare these models using a deviance test. Now, ... | g60819 | [
0.02126910723745823,
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0.012928091920912266,
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-0.0... |
<p>A company has 20 employees, 12 males, and 8 females. Suppose we need to form a committee of 5 employees.</p>
<ol>
<li><p>How many ways are there to form this committee if we need 3 males and 2 females?
I believe this is a permutation problem and calculate it as one.
12 * 11 * 10 * 8 * 7 = 73,920</p></li>
<li><p>How... | g60820 | [
0.019350072368979454,
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0.012323655188083649,
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0.006769753061234951,
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0.029... |
<p>I asked this question:</p>
<p><a href="http://stats.stackexchange.com/questions/83712/compare-the-variances-of-several-groups?noredirect=1#comment164193_83712">Compare the variances of several groups</a></p>
<p>The Levene's method only test all groups. How can I identify the groups that have a different variances... | g60821 | [
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0.012740242294967175,
0.03876270353794098,
0.0063654049299657345,
... |
<p>I have made this linear regression model:</p>
<pre><code>mtcars_lm <- lm(mpg ~ drat + hp, mtcars)
</code></pre>
<p>Using the effects package, I can predict values of <code>mpg</code> for every value of <code>hp</code> between 70 and 150, plus get a confidence interval for each value of <code>mpg</code>:</p>
<p... | g49410 | [
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0.01272561214864254,
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0.07234254479408264,
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-0.0556773878633976,
0.0032024476677179337,
0.061372000724077225,
0.07346167415380478,
-0... |
<p>I have n rooms (which can be considered as states) and a sensor on my robot which gives me a probability array of what room it is in (this array is of size n and its sum is 1).
At every timestamp (the timestamps are regularly spaced, say 5 seconds) the robot takes a measurement and stores it.</p>
<p>Moreover, I kno... | g60822 | [
-0.006578199565410614,
0.002416611649096012,
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0.03303411975502968,
... |
<p>As title, I need to draw something like this:</p>
<p><img src="http://i.stack.imgur.com/KYQ5V.jpg" alt="alt text"></p>
<p>Can ggplot, or other packages if ggplot is not capable, be used to draw something like this?</p> | g17109 | [
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-0.019632... |
<p>I have database of 78706 resident incidents in aged care facilities (5 years of data).
I want to to learn and implement a tool allowing analyzing these data using following attributes:</p>
<ol>
<li>Resident</li>
<li>Date/Time</li>
<li>Location</li>
<li>Result</li>
<li>Injury</li>
</ol>
<p>I want to be able to get ... | g46772 | [
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0.045247796922922134,
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0.09960721433162689,
-0.02... |
<p>In order to calibrate a confidence level to a probability in supervised learning (say to map the confidence from an SVM or a decision tree using oversampled data) one method is to use Platt's Scaling (e.g., <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.60.5153&rep=rep1&type=pdf" rel="nofo... | g60823 | [
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-0.03121909312903881,
0.02034529484808445,
0.05549495667219162,
0.0699896365404129,
0.008... |
<p>This question is related to my previous question <a href="http://stats.stackexchange.com/questions/5011/bias-for-kernel-density-estimator-periodic-case">Bias for kernel density estimator (periodic case)</a></p>
<p>A kernel $K(x)$ is of the order $p$ if
$$\int_{-\infty}^{\infty}K(x)x^{j}=\delta_{0,j}\ j=0,...p-1$$ ... | g60824 | [
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0.02920563519001007,
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0.03831486776471138,
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0... |
<p>I'm not a statistician by education, I'm a software engineer. Yet statistics comes up a lot. In fact, questions specifically about Type I and Type II error are coming up a lot in the course of my studying for the Certified Software Development Associate exam (mathematics and statistics are 10% of the exam). I'm havi... | g17113 | [
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0.026445947587490082,
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0.0016263952711597085,
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0.08597011864185333,
... |
<p>As an outsider, it appears that there are two competing views on how one should perform statistical inference. </p>
<p>Are the two different methods both considered valid by working statisticians? </p>
<p>Is choosing one considered more of a philosophical question? Or is the current situation considered problemati... | g60825 | [
0.09187152236700058,
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0.08658821135759354,
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0... |
<p>I have a dataset that includes individual responses to a series of questions.
Participants played a game with one of two roles (hider, seeker) and indicated their response with a binary variable (0:BLUE, 1:RED).
There were 4 within subject conditions and 3 between subject conditions.</p>
<p>I would somehow like to ... | g17122 | [
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0... |
<p>I'm running AB tests on my website homepage, with 8 different variations. You can read about the purpose of the test here if you need to (not essential) - <a href="http://westiseast.co.uk/blog/ab-split-testing-a-promise-ogilvy/" rel="nofollow">http://westiseast.co.uk/blog/ab-split-testing-a-promise-ogilvy/</a></p>
... | g287 | [
0.02503264881670475,
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0.023959986865520477,
0.025739949196577072,
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0.03534410893917084,
0.026203438639640808,
0.021230967715382576,
-0.018520722165703773,
0.0... |
<p>I was taught that I can do a goodness of fit test for binomial model by comparing it to the saturated mode with drop in deviance test. What should I do when my binomial model has over-dispersion? Can I still use the goodness of fit test using drop in deviance?</p>
<p>And how do I accomplish this that using R (if th... | g60826 | [
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0.007141329813748598,
0.014019615948200226,
... |
<p>I have a question regarding clustering. I have a symmetric matrix of 50 specialties (50 X 50) where each cell represents the number of observations related to each combination of specialties. Some combinations in this matrix do not exist in the data (coded with zero frequency) and the diagonal is zero. I would like ... | g60827 | [
0.04129470884799957,
0.01078070793300867,
0.014031152240931988,
-0.029175331816077232,
0.00413342984393239,
-0.02570072002708912,
0.029714131727814674,
0.019014274701476097,
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-0.010205530561506748,
0.004533084575086832,
0.013029699213802814,
0.06082885339856148,
0.003... |
<p><strong>I simplified this a fair bit after finding a draft version of the Imbens and Rubin chapter.</strong></p>
<p>I am interested in estimating a constant multiplicative treatment effect from a randomized experiment. I believe the DGP for my observed data to be something like
\begin{equation}
y_i=y_i^C\cdot(1+\be... | g60828 | [
-0.041016705334186554,
-0.052068572491407394,
-0.021322669461369514,
-0.006523310672491789,
0.006816328968852758,
-0.00976383313536644,
0.02695968560874462,
0.03658679872751236,
0.0003987412783317268,
-0.042457666248083115,
-0.01649056188762188,
0.05349451303482056,
-0.028140418231487274,
... |
<p><strong>I'm looking to learn about the main/popular alternatives when it comes to estimating correlations that I've missed in the following list</strong>. The best answer will provide a reference (can be Wikipedia), a quick description and a motivation/purpose/reason to use. </p>
<p>Here's the ones that I'm already... | g60829 | [
0.03921666368842125,
-0.04765334725379944,
-0.013489707373082638,
-0.02209167182445526,
0.019854912534356117,
-0.03785679116845131,
0.019996976479887962,
-0.06302403658628464,
-0.018673088401556015,
0.010407064110040665,
0.004113779868930578,
0.0030424799770116806,
0.04863912612199783,
0.0... |
<p>I am conducting a research on the effect of burnout on anxiety, tiredness and sleep, before a particular event and after an event.</p>
<p>There is one sample of which different data was collected over 6 years. There have been 5 different measurements (Time1 T2 T3 T4 T5)
at T1 T2 and T3 burnout was measured,
tiredn... | g17128 | [
0.017033670097589493,
-0.052838653326034546,
-0.021143419668078423,
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-0.015903402119874954,
0.0056543052196502686,
-0.029049115255475044,
0.005831244867295027,
0.015088455751538277,... |
<p>Let $X_1,\dots X_n$ be i.i.d. and $N(\mu,\sigma^2)$ distributed. Let
$$\overline{X} = \frac{1}{n}\sum_{i=1}^n X_i$$ and
$$S^2=\frac{1}{n-1}\sum_{i=1}^n (X_i -\overline{X})^2$$</p>
<p>Then I know that through the distribution of $S^2$ one can very easily find its variance to be
$$\mathbf{Var} (S^2)=\sigma^4 \cdot... | g60830 | [
0.003168134717270732,
0.011238094419240952,
-0.04234665632247925,
-0.020185310393571854,
0.007854502648115158,
0.0008963305153883994,
0.027777675539255142,
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-0.03624464571475983,
-0.059221312403678894,
0.037357620894908905,
0.005040133837610483,
... |
<p>My problem is:</p>
<p>Evaluate:</p>
<p>$$\sum_{i=0}^n i{n \choose i}$$</p>
<p>I only know that $$\sum_{i=0}^n{n \choose i} = 2^n$$ not so sure when an "i" is added.</p>
<p>What is the step of this evaluation?</p> | g60831 | [
-0.0306782778352499,
0.01717243902385235,
-0.014877929352223873,
0.04925500601530075,
0.02798096463084221,
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0.03179207444190979,
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-0.017591051757335663,
-0.08215136080980301,
0.04396731033921242,
-0.02588467486202717,
0.03054... |
<p>When building a CART model (specifically classification tree) using rpart (in R), it is sometimes obvious that there are variables (X's) that are meaningful for predicting some of the outcome (y) variables - while other predictors are relevant for other y's only.</p>
<p><strong>How can it be estimated, which explan... | g60832 | [
0.0005752700963057578,
-0.03406186029314995,
0.010428676381707191,
-0.04674758389592171,
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-0.014565793797373772,
-0.016405245289206505,
0.017845526337623596,
0.03766997903585434,
0.... |
<p>I'm coding an app, a part of which is graphing values from a database.</p>
<p>The graph plots the average value of every 10% of the values up to 100% so there are ten points along the x-axis. The graph shows a trend of the lifetime of the stats. Hopefully this makes sense.</p>
<p>I need to decide on a scale for th... | g60833 | [
0.01739048771560192,
0.03495030105113983,
-0.025028526782989502,
-0.004694870673120022,
-0.02925276756286621,
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0.008808471262454987,
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0.006040557753294706,
0.02728434093296528,
0.021282650530338287,
0.06612200289964676,
0.03... |
<p>I have a question on multiple polynomial regression and the absolute minimum amount of points in the different terms. The minimum amount of points required for a second order polynomial would (in one variable) be three and in general it would p+1, p being the polynomial order. I have the intuition this generalizes t... | g17134 | [
0.023502029478549957,
0.032578855752944946,
-0.006130543537437916,
-0.019277062267065048,
0.022918542847037315,
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0.01570984162390232,
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0.01687714084982872,
-0.0037640053778886795,
0.038449909538030624,
0.011919498443603516,
-... |
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