question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Why are the <a href="https://en.wikipedia.org/wiki/Geometric_distribution">geometric distribution</a> and <a href="http://en.wikipedia.org/wiki/Hypergeometric_distribution">hypergeometric distribution</a> called "geometric" and "hypergoemetric" respectively?</p>
<p>Is it because their pmfs take some special form? T... | g29080 | [
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<p>Let's say that $F(k; n, p) = \Pr(k \leq X)$ is the cumulative binomial distribution for $X \sim B(n, p)$. I am trying to solve for the smallest $i$ such that $F(i; n + i, p) > \alpha$ for some $\alpha$.</p>
<p>I would use the inverse binomial distribution function to find this, except the $n$ parameter changes.<... | g706 | [
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<p>As part of a larger analysis, I'm interested in examining the relationship between an interval level variable and a four category nominal variable. In this case, the interval variable is the independent variable and the four category nominal variable is the dependent variable. I'm interested in whether there is a st... | g29082 | [
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<p>Could someone shed some light into the implementation of the GARCH(1,1) model contained in page6 of the following document? <a href="http://www-stat.wharton.upenn.edu/~steele/Courses/956/RResources/GarchAndR/WurtzEtAlGarch.pdf" rel="nofollow">http://www-stat.wharton.upenn.edu/~steele/Courses/956/RResources/GarchAndR... | g68870 | [
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<p>Suppose I have a Finite State Automata with various states and probabilities of state transitions. Does mathematics exist to determine the probability of NOT reaching a state in the FSA given some n number of state changes? </p> | g68871 | [
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<p>I'm working on a meta-analysis. Some studies report d', others report accuracy (hits and false alarms). I would like to transform all the data into the same measure, d' (also c). However, for many studies, I only have the mean and sd of the accuracy measures. If I compute d' from the mean hit and false alarms, the o... | g68872 | [
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<p>Is there a PDF for a distribution defined as a sum of squares of random variables pulled from a family of normal distributions with different standard deviation?</p>
<p>Is there a way of analytically writing the PDF of such a distribution as a hypergeometric function without prior normalization to make all the unde... | g49816 | [
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<p>I analyze ethnic differences in risk of cardiovascular events (CVD) in a cohort study of patients with coronary heart disease. It is known that immigrants have higher risk of CVD and I intend to show this via Cox regression.
However, my results fail to prove what is both plausible and well known, i.e immigrants do n... | g68873 | [
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<p>Say I have search data like this</p>
<p><code>AvgCost QualityScore SearchShare</code></p>
<p><code>3.12 6 0.6364</code></p>
<p>Where AvgCost is a continuous numerical variable, qualityScore is a categorical variable with values 1-10, and SearchShare is a percentage...I am wondering how to t... | g68874 | [
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<p>Accidentally, I found (by simulation) that the range of a normally distributed sample is related to the estimator of the standard deviation:</p>
<p>$$X \sim \mathcal{N}\left(\mu, \sigma\right)$$</p>
<p>$$s(X) = \frac{1}{3}\left(\max(X) - \min(X)\right)$$</p>
<p>Why is that? I can't find any references. Is it rela... | g68875 | [
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<p>I did run PCA on 17 quantitative variables in order to obtain a smaller set of variables that is principal components to be used in supervised machine learning for classifying instances into two classes. After PCA the PC1 accounts for 31% of the variance in the data, PC2 accounts for 17%, PC3 accounts for 10%, PC4 a... | g29088 | [
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<p>I am looking for a statistical model to detect grouping patterns among a population X of n element with respect to their association with k elements of population Y. In modern marketing, an example of that would be "customers who bought X also bought Y", such as on Amazon etc.</p>
<pre><code>X (person) Y (purchas... | g29090 | [
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<p>I have been implementing this paper:</p>
<p><a href="http://www.tandfonline.com/doi/abs/10.1080/03610918.2011.575506#.UrijOLS_UhI" rel="nofollow">http://www.tandfonline.com/doi/abs/10.1080/03610918.2011.575506#.UrijOLS_UhI</a></p>
<p>I can send a copy should anybody require it.</p>
<p>I think that my implementati... | g68876 | [
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<p>I'm trying to put together a self-directed math curriculum to prepare for learning data mining and machine learning. This is motivated by starting <a href="https://www.coursera.org/course/ml">Andrew Ng's machine learning class</a> on Coursera and feeling that before proceeding I needed to improve my math skills. I g... | g49612 | [
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<p>I have a set of samples from a random variable, is there any method so that I can confirm/check to know whether they follow a laplace distribution in an statistically rigorous way?</p>
<p>I am very new to statistics and would really be grateful if you could at least point me towards some litrature.</p>
<p>Thanks</... | g68877 | [
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<p>I have a multinomial logit model with three outcome categories and a variety of (primarily binary) independent variables. </p>
<p>How would I go about bootstrapping the average treatment effect and its confidence interval of a binary variable?</p>
<p>Right now my procedure is as follows:</p>
<p>After running the... | g68878 | [
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<p>I'm familiar with the bag of words/Naive bayes sentiment analysis for text (e.g. <a href="http://streamhacker.com/2010/05/10/text-classification-sentiment-analysis-naive-bayes-classifier/" rel="nofollow">http://streamhacker.com/2010/05/10/text-classification-sentiment-analysis-naive-bayes-classifier/</a>)</p>
<p>I ... | g68879 | [
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<p>Since the population variance can never be estimated, will we always have a t-distribution instead of normal?</p> | g68880 | [
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<p>There are $m$ normally distributed, independent random variables $N_1, \ldots, N_m$ with distinct means $\mu_1, \ldots \mu_m$ and standard deviations $\sigma_1, \ldots, \sigma_m$. Then, we observe a permutation of the numbers $\pi = \{1, \ldots, m\}$. How can we efficiently compute the conditional expectation of the... | g29096 | [
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<p>Many of the articles discuss about the relationship between mean and standard deviation of numbers above zero stating that mean should be greater than standard deviation</p>
<p>But if the numbers or the data has negative integers with scores ranging from -10 to +10, is it necessary that mean should be greater than ... | g68881 | [
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<p>I've been thinking about this problem. The usual logistic function for modeling binary data is:
$$
\log\left(\frac{p}{1-p}\right)=\beta_0+\beta_1X_1+\beta_2X_2+\ldots
$$
However is the logit function, which is an S-shaped curve, always the best for modeling the data? Maybe you have reason to believe your data does... | g68882 | [
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<p>Suppose that I divide my data for modelling purposes into training, testing, and validation which will then be deployed for an application (<a href="http://stats.stackexchange.com/questions/19048/what-is-the-difference-between-test-set-and-validation-set">as in the response to this question</a>). Why not incorporate... | g857 | [
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<p>I am using the Holt-Winters' exponential smoothing technique to forecast expenditure data 2 years into the furture. The monthly data has an increasing trend and annual seasonality.</p>
<p>I'm using MS Excel with the Solver add-in to calculate the optimal values of $\alpha$, $\beta$ and $\gamma$ to give the smallest... | g68883 | [
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<p>I am interested in building an index that tracks how accurate economists are at predicting several US economic statistics:</p>
<ul>
<li>US Jobless claims number: comes out weekly, ranges from 100k to 400k, usually in eight year cycles</li>
<li>U Michigan Consumer Confidence: comes out bi-weekly, ranges from 50 to 1... | g42298 | [
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<p>Stuck at a pretty weird research design and would like to get some input on how to go about calculating power.</p>
<p>A researcher would like to randomize four groups into four different interventions (one of them being the proposed new standard, the other three are currently used practices), followed by comparing ... | g68884 | [
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<p>I was wondering from the view of dividing the topics of statistical theory into inference part and non-inference part, what inference topics and non-inference topics statistical theory is covering?</p>
<p>By inference, I mean the task in logic to reach some conclusion from some premises. Probabilistic inference is ... | g39147 | [
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<p>I was asked this question with $(n, k) = (400, 220)$ in an interview. Is there a "correct" answer?</p>
<p>Assume the tosses are i.i.d. and the probability of heads is $p=0.5$. The distribution of the number of heads in 400 tosses should then be close to Normal(200, 10^2), so that 220 heads is 2 standard deviation... | g29100 | [
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<p>Let's say we had 5 distributions: A,B,C,D,E. </p>
<p>An ANOVA test would tell us whether or not all of the means are equal, and thus a low p-value would mean at least one of the means is unlikely to be equal to the mean of the whole population of distributions. Is this a correct interpretation?</p>
<p>If so, I'm l... | g29101 | [
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<p>I need a graduate level, mathematically rigorous textbook on multivariate analysis and inference to enhance myself. I've been reading the <a href="http://www-stat.stanford.edu/~tibs/ElemStatLearn/" rel="nofollow">Elements of Statistical Learning</a> and doing the problems within, but I need a book with other focuses... | g29103 | [
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<p>I have a setting where I normally would model the variability in measurements by a linear mixed model which would look in R as follows.</p>
<pre><code>require(lme4)
lmer(measure ~ equipment + (1|operator) + (equipment|batchid), data=mydataset)
</code></pre>
<p>So basically </p>
<ul>
<li>a fixed effect of equipme... | g68885 | [
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<p>Example of z-score computation:</p>
<p>1 - E.g.</p>
<pre><code>Time-series: [0, 0, 0, 0, 1]
Current: 1
Mean: 0.2
Std: 0.44721
Z = (1 - 0.2) / 0.44721 ~= 1.7888
</code></pre>
<p>2 - E.g.</p>
<pre><code>Time-series: [100, 100, 100, 100, 1000]
Current: 1000
Mean: 280
Std: 402.49224
Z = (1000 - 280) / 402.49224 ~= 1... | g68886 | [
-0.0471523180603981,
0.037078507244586945,
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0.0454617403447628,
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0.08751829713582993,
0.08222108334302902,
0.043617375... |
<p>I am doing image processing and I want to calculate the variance of a histogram of pixel intensities. </p>
<p>The first method I have tried:
The images store the pixels values using double precision numbers, however to make a histogram, they need to be scaled so that the can be grouped in to bins. For example into ... | g68887 | [
0.004602112807333469,
0.08605226874351501,
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0.02487979084253311,
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0.03566087782382965,
0.05468699336051941,
0.0234... |
<p>everyone, I'm new at the statistical analysis so I need some help from more experienced people.
I'm working with biological data from gene expression analysis. I have 5 treatments (1 parental toxin; 3 compounds resulting from the metabolism of the parental toxin -let's calll them A, B and C), and a control, each one... | g68888 | [
0.03459838405251503,
-0.07416747510433197,
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0.00688153738155961,
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0.01284676045179367,
0.01056306529790163,
0.030368760228157043,
0.0049... |
<p>I'm relatively new to stats, and I have a large dataset of strings (n=114541) for which I'm interested in a binary event: whether X occurs or not (specifically, whether a specific language construct is present in a given string). X occurs rarely (443/n). X is poisson-distributed.</p>
<p>The strings in the dataset a... | g68889 | [
0.012933015823364258,
0.008218268863856792,
0.002147104823961854,
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0.02072104625403881,
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0.0013277510879561305,
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0.028037628158926964,
0.001490308321081102,
-0.... |
<p>I'm referring to something like this:</p>
<p><img src="http://i.stack.imgur.com/bQ8b1.png" alt="alt text"></p>
<p>suggested dataset for showing a solutions: </p>
<pre><code>data(mtcars)
plot(hclust(dist(mtcars)))
</code></pre> | g68890 | [
-0.024524886161088943,
0.011376324109733105,
-0.015986105427145958,
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-0.04492119327187538,
0.011056124232709408,
0.006127750035375357,
0.09728933870792389,
0.0... |
<p>Let ${X_t}$, $t=...-2,-1,0,1,2...$ be a stochastic process that satisfies:</p>
<p>$X_t=\rho X_{t-1}+\varepsilon_t$</p>
<p>with $|\rho|<1$ and $\varepsilon_t$ is a white noise. In that case, we also know that there is a $\beta$ such that $|\beta|>1$ and another white noise $\eta_t$ such that ${X_t}$ also sati... | g29109 | [
0.023935379460453987,
0.009455126710236073,
0.0010144738480448723,
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0.0006521823233924806,
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0.06023748591542244,
0.03661666437983513,
0... |
<p>In their paper Acosta-Ormaechea and Morozumi (2013) propose a use of GMM for estimating a regression in which they try to find the impact of reallocating public expenditure from some unproductive to those productive, and I am trying to write a monograph, so I would like to know how can I use the same method of estim... | g68891 | [
-0.01455723401159048,
0.031109904870390892,
-0.0063446867279708385,
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0.008134765550494194,
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0.08061988651752472,
0.026262788102030754,
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0.02167566306889057,
-0.022464968264102936,
0.00810321792960167,
0.05991464480757713,
-0.00... |
<p>I am working with a regression problem. I have some features which are only available for a few instances. But with those few instances based on those features we can build a model which gives reasonable results.
At the same time I have other features which are available for almost all instances. How should I combi... | g68892 | [
0.028952158987522125,
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0.050279680639505386,
0.0075984615832567215,
0.0025246981531381607,
0.02324090711772442,
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-0.03225027397274971,
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0.020491592586040497,
0.056643322110176086,
... |
<p>I have what I guess is a simple question really and it's probably as much about the English language as about stats. I should explain that this isn't my strong point at all but I have to write up results on some experiments I've carried out and I don't know how best to explain the way I'm comparing the results.</p>
... | g29110 | [
0.07761353999376297,
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0.05877716466784477,
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0.05143530294299126,
0.0367145799100399,
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0.008476275019347668,
0.0003874611866194755,
0.004975370597094297,
-0.0026268132496625185,
0.0... |
<p>I am playing around with SP500 data from MASS package and from observation of the ACF and PACF there seem to be no significant autocorrelation. Now I want to model the volatility of the returns but I also want a mean equation. I'm not sure how I will get my mean equation as the ACF and PACF suggest that I can't use ... | g29111 | [
0.03601404279470444,
-0.04097776859998703,
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0.0254158116877079,
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0.051531024277210236,
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-0.04391748830676079,
0.03507488593459129,
0.033035047352313995,
0.07308529317378998,
-0.0... |
<p>Suppose I have a random variable X which can take integer values 0 through 99. It can be, for example, numbers written on balls in a large urn. I have three hypotheses about the distribution of these numbers on the balls: $H_0$ says each number is just as likely as every other number; $H_1$ says that there's a 90% c... | g23853 | [
0.009675945155322552,
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0.0002937807876151055,
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0.04889689385890961,
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0.032097551971673965,
... |
<p>What are the differences between planning, prediction and forecasting in relation to data mining and business intelligence?</p>
<p>It would be great if you could provide some concrete examples of these three concepts.</p>
<p>I don't have enough experience to understand it.</p> | g68893 | [
0.03916237875819206,
0.03724581375718117,
0.01576920785009861,
0.0496942400932312,
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0.032872870564460754,
0.06824102997779846,
-0.0169860... |
<p>I have an RNA_Seq dataset (FPKM values) obtained from the ENCODE Caltech datasets for K562 cells; I also have 6 different lists of genes and I want to show that the expression values of my panel of genes is not random. Therefore, I decided to use R and perform bootstrapping.</p>
<p>Bootstrapping, as far as I know, ... | g68894 | [
-0.00003236917473259382,
-0.008373884484171867,
0.006532908417284489,
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0.03223562613129616,
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0.03765735775232315,
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-0.0076908026821911335,
-0.0016984818503260612,
0.022501837462186813,
0.07064986228942871,... |
<p>I'm interested in a good reference for results concerning asymptotic properties of maximum likelihood estimators. Consider a model $\{f_n(\cdot \mid \theta): \theta \in \Theta, n \in \mathbb N\}$ where $f_n(\mathbf x \mid \theta)$ is an $n$-dimensional density, and $\hat \theta_n$ is the MLE based on a sample $X_1, ... | g68895 | [
0.03788066655397415,
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0.0071499706245958805,
0.009940947405993938,
0.06955201178789139,
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0.07401929050683975,
0.028430892154574394,
-0.012029958888888359,
0.0011576424585655332,
-0.0132152633741498,
0.015158185735344887,
0.03374211862683296,
0.0539... |
<p>See the cross-post at <a href="http://stackoverflow.com/questions/16659749/getting-the-ellipse-function-to-match-the-dataellipse-function-in-r">http://stackoverflow.com/questions/16659749/getting-the-ellipse-function-to-match-the-dataellipse-function-in-r</a>.</p>
<hr>
<p>So I am sampling from a multivariate norma... | g29117 | [
0.04243342950940132,
-0.038374681025743484,
-0.012096402235329151,
-0.005727636162191629,
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-0.07027410715818405,
0.034453850239515305,
-0.004880308639258146,
0.003647533943876624,
0.023025497794151306,
-0.019782135263085365,
0.04519141465425491,
0.03189924731850624,
-... |
<p>So, I am not a statistician, but a burgeoning mathematician. Here is something that is perplexing me in statistics, however. My apologies if the question is silly, on one hand, or just not solvable, on the other. Also, any online resources would be helpful. I am looking to learn:</p>
<p>Let's say we have indepe... | g42441 | [
0.0515005886554718,
-0.04105512797832489,
-0.019908932968974113,
-0.04501834884285927,
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-0.0776086375117302,
-0.008342229761183262,
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0.007458455394953489,
-0.022815903648734093,
0.0109739163890481,
-0.0024651263374835253,
0.013121460564434528,
0.0... |
<p>When I run this code:</p>
<pre><code>require(nlme)
a <- matrix(c(1,3,5,7,4,5,6,4,7,8,9))
b <- matrix(c(3,5,6,2,4,6,7,8,7,8,9))
res <- lm(a ~ b)
print(summary(res))
res_gls <- gls(a ~ b)
print(summary(res_gls))
</code></pre>
<p>I get the same coefficients and the same statistical significance on t... | g68896 | [
-0.010430464521050453,
-0.05130718648433685,
-0.009597067721188068,
-0.055049434304237366,
0.007399342488497496,
-0.011156689375638962,
0.02024526707828045,
-0.0237200278788805,
-0.051703374832868576,
-0.012661885470151901,
-0.05645323544740677,
0.044554702937603,
0.056089017540216446,
-0.... |
<p>I am using the <a href="http://en.wikipedia.org/wiki/Akaike_information_criterion#AICc" rel="nofollow">corrected AIC</a> to select the lag order in a simple AR(p) model. I chose the the AICc since my sample is fairly small (n=135). The AICc minimal model is the AR(15). To me it seems like an overfit to include 15 la... | g68897 | [
0.05074354633688927,
-0.031926680356264114,
-0.015250425785779953,
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0.03703451529145241,
-0.04510747268795967,
0.03846915066242218,
0.01602035015821457,
-0.06690036505460739,
0.01747100241482258,
0.05443466454744339,
-0.008877338841557503,
0.08639612048864365,
-0.01328... |
<p>Running a logistic regression we get p-values for all the input variables which helps us choose significant inputs. Similarly can we use the classification trees to pick variables that are split, and use those variables in the model? I think the fact that splitting the dataset on a variable leads to lower classifica... | g68898 | [
-0.015367135405540466,
0.004066996742039919,
0.008502993732690811,
-0.036033231765031815,
0.010143055580556393,
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0.03929512947797775,
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-0.011110054329037666,
0.006627260707318783,
0.023457037284970284,
0.010199055075645447,
... |
<p>I am ranking candidate models using Akaike information criterion (AIC).
All my models have positive -2*LL (log likelihood) values which as far as I understand is expected under certain circumstances and not much of a problem...</p>
<p>...unless - and this is just me wondering - I want to rank models using AIC=-2*LL... | g68899 | [
-0.031019246205687523,
-0.029516464099287987,
-0.005587630905210972,
-0.03026602976024151,
0.0015899199061095715,
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0.015945089980959892,
0.01653190329670906,
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0.05512234941124916,
0.0000025288061351602664,
0.024705814197659492,
0.1011255532503128,
... |
<p>The Bradley–Terry–Luce(BTL) model states that $p_{ji} = logit^{-1}(\delta_j - \delta_i)$, where $p_{ij}$ is the probability that object $j$ is judged to be "better", heavier, etc, than object $i$, and $\delta_i$, and $\delta_j$ are parameters.</p>
<p>This seems to be a candidate for the glm function, with family =... | g29121 | [
-0.02775654010474682,
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0.008629396557807922,
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0.07816120982170105,
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-0.013434509746730328,
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0.003137946594506502,
0.13588295876979828,
-0.0... |
<p>My data is a time series of employed population, L, and the time span, year.</p>
<pre><code>n.auto=auto.arima(log(L),xreg=year)
summary(n.auto)
Series: log(L)
ARIMA(2,0,2) with non-zero mean
Coefficients:
ar1 ar2 ma1 ma2 intercept year
1.9122 -0.9567 -0.3082 0.0254 -3.5904 ... | g29122 | [
0.004313443787395954,
-0.05868315324187279,
0.015241419896483421,
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0.014847430400550365,
0.0819375216960907,
0.0010858328314498067,
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0.03011515364050865,
0.0003882490564137697,
0.056889813393354416,
0.06722120940685272,
-0.... |
<p>Hello fellow number crunchers</p>
<p>I want to generate n random scores (together with a class label) as if they had been produced by a binary classification model. In detail, the following properties are required:</p>
<ul>
<li>every score is between 0 and 1</li>
<li>every score is associated with a binary label w... | g68900 | [
0.009051320143043995,
-0.053644079715013504,
-0.0038849920965731144,
-0.0619087815284729,
0.0335216224193573,
-0.024142399430274963,
0.0033181870821863413,
0.026740072295069695,
-0.03044426068663597,
-0.012793663889169693,
-0.0039000820834189653,
-0.005534857977181673,
0.05268887057900429,
... |
<p>Say I have 1000 unique websites in my sample.</p>
<p>Each website has two categorical variables assigned to it:</p>
<ul>
<li>PolicyDomain (e.g. 0 = "health", 1 = "defence", etc... up to 42).</li>
<li>Community (e.g. "Community1", "Community2" ... up to "Community 6").</li>
</ul>
<p>How do I find out whether there... | g11701 | [
0.010165716521441936,
0.033589620143175125,
-0.028800491243600845,
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0.07021279633045197,
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0.034450460225343704,
0.03597262129187584,
-0.033954963088035583,
-0.009771646000444889,
-0.0018226986285299063,
0.04527052491903305,
0... |
<p>I am working on a pattern identification/classification problem on an imbalanced dataset, with target to non target proportion in population approx as 1%:99%. There are around 0.5 million records in my dataset.</p>
<p>I am restricted to use SAS E-Miner for this analysis. Currently I am using the following approach:... | g68901 | [
-0.006612819153815508,
-0.013528277166187763,
-0.015294717624783516,
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0.027034947648644447,
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0.02726396545767784,
0.034738194197416306,
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0.019660484045743942,
0.018785836175084114,
0.042944952845573425,
0.05926457419991493,
0... |
<p>Since the KM estimator does not allow for any other state other than the event of interest is it safe to assume that $S(t=\infty) = 0$ ? Or can it be that $S(t=\infty) > 0$ </p> | g68902 | [
0.022684412077069283,
0.010247637517750263,
0.0017016039928421378,
0.010569815523922443,
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0.0011498715030029416,
0.0497097410261631,
0.01554674468934536,
0.014724417589604855,
-0.05987641215324402,
0.023522846400737762,
-0.031173426657915115,
-0... |
<p>I am running an experiment where I have a finite set of raters and a finite set of items, and raters have to provide their subjective judgment about each item. The goal is to measure the importance of those items for the raters.</p>
<p>For every item, each rater uses a Likert-like scale (1= Unimportant, 2= Of Littl... | g42830 | [
0.002445506863296032,
0.014204309321939945,
0.012262338772416115,
-0.04972555860877037,
0.021633315831422806,
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-0.02094980701804161,
0.015146296471357346,
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0.0076892985962331295,
0.05448884516954422,
-0.01204801443964243,
0.03776755928993225,
0.067... |
<p>I have 1000 observations with 2 continuous variables :</p>
<blockquote>
<p>Observation ID | X | Y</p>
</blockquote> | g68903 | [
-0.015658793970942497,
0.01650959625840187,
-0.008244622498750687,
-0.018710032105445862,
0.04651181027293205,
-0.022705601528286934,
0.022002367302775383,
0.062076419591903687,
-0.0021104614716023207,
-0.008866301737725735,
0.0116698257625103,
0.0492425337433815,
0.027614938095211983,
0.0... |
<p>I am looking for a metric to evaluate the quality of a classifier which answers the question for a class of an object with a probability per known class. Say I use the classifier to classify an object of class A and the classifier classifies the object with 75% probability as A and 25% probability as C.</p>
<p>One ... | g68904 | [
0.03096838667988777,
0.0016677610110491514,
0.011777539737522602,
-0.03535451740026474,
0.013506966643035412,
-0.014926239848136902,
0.03307461738586426,
0.028843380510807037,
-0.01926877163350582,
-0.04889291524887085,
0.0788486897945404,
-0.027802683413028717,
0.068966805934906,
0.005544... |
<p>The <a href="http://en.wikipedia.org/wiki/Mantel_test">Mantel test</a> is usually applied to symmetric distance/difference matrices. As far as I understand, an assumption of the test is that the measure used to define differences must be at least a semi-metric (meet the standard requirements of a metric but not the ... | g39176 | [
-0.026175696402788162,
0.009278678335249424,
-0.012081481516361237,
-0.05744656175374985,
0.008734120987355709,
-0.03620439022779465,
0.05451950058341026,
0.03150931000709534,
-0.06126733869314194,
-0.01158573292195797,
-0.033342622220516205,
-0.026907308027148247,
0.00046555313747376204,
... |
<p>In my previous question titled <a href="http://math.stackexchange.com/questions/183614/conditional-combinations-of-balls-in-bowls">"Conditional combinations of balls in bowls"</a>, is there a distribution to fit $k$ when $d \gg M$? I mean, when $d$ is so large, what is the distribution of the total number of balls?<... | g29125 | [
0.03709929436445236,
0.08026771247386932,
-0.0033239100594073534,
-0.04314535856246948,
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0.01080512534826994,
0.02231285162270069,
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0.009439051151275635,
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0.05405483767390251,
-0.0... |
<p>I am trying to predict a binary outcome with a model that includes a random effect using survey data. I've included a description of the sampling design below, so feel free to comment on my survey weighting approach. My primary question is how to include a random effect in the survey weighted model. Here is the co... | g29126 | [
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0.0... |
<p>using a monte carlo simulation
Im just trying to test the null hypothesis for normality in a sample that splits N values into 2, using the first N/2 values to estimate the sample mean and variance, and the second N/2 values to apply the test based on these moment estimates (the Normal distribution tested against wi... | g68905 | [
0.039899133145809174,
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<p>I'm modelling a time series using high order markov chain and estimate the transition probability of the equivalent first order markov chain.</p>
<p>The problem is that some of transition in the equivalent first order markov chain from state i to state j doesn't occur in the training dataset at all. How to handle t... | g68906 | [
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<p>Let $B(t)$ and $W(t)$ be two independent Brownian motions.
Show that $X(t)=\frac{B(t)+W(t)}{\sqrt2}$ is also a Brownian motion. Find the correlation
between $B(t)$ and $X(t)$.</p> | g68907 | [
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<p>Suppose $X \sim N (50, 20.5)$ represents a population. If $X_1, X_2, …, X_n$ is a random sample from this population, find $n$ such that $\mathbb{P}(X_1 + X_2 + … + X_n > 2000) = 0.95 $</p> | g68908 | [
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<p>I'm looking for resources to help me solve an issue of resource prediction. We can make a number of observations of the resource over time, but the way in which the resource changes is affected by both us and other players, furthermore the amount of resource as it appears to us can be false in some circumstances. I'... | g68909 | [
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<p>I'm going to implement HOG as my features descriptor.<br>
But there are some things that make me confused:</p>
<p>For example:<br>
If we have an image with size of 10 x 20 </p>
<ol>
<li><p>If we want to compute the HOG of that image (not overlay), and we determine that the<br>
cellsize would be 1x1 and the block... | g29132 | [
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<p>I am doing a LMM in R and would like to know if I need to do a planned contrast or a post-hoc analysis. </p>
<p>From my understanding, the LMM in R already provideds me a planned contrasts and if I have many types in each variable, you can just change the baselines of model to see all angles of it.</p> | g29133 | [
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<p>I am using a Likert scale for a group of 3 questions.</p>
<ol>
<li>Strongly Agree</li>
<li>Agree</li>
<li>Undecided</li>
<li>Disagree</li>
<li>Strongly Disagree</li>
</ol>
<p>I have 3 questions with these possible responses under the category "Effectiveness". Can the responses in the 3 questions be combined to giv... | g49817 | [
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<p>I am modelling a simple model of how many points are scored in total in basketball matches. I have a dataset of 500 matches. Pre game I know which team are favorite to win, for all the matches in my dataset. For every minute of the matches, I observe the difference in score. The difference in score is a factor: X fo... | g68910 | [
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<p>This problem occurred to me a couple of days ago, in the context of a game with a leaderboard. I wondered, given only the leaderboard, could I estimate parameters for the distribution of scores? </p>
<p>Estimation of order statistics is a reasonably well understood problem, but as far as I can see all require kno... | g68911 | [
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<p>I wanted to ask whether it was possible to use the auto.arima function to identify subset ARIMA models rather than those of pure lags? I have identified a model in Stata in subset lags that performs well and wanted to cross check this with the <code>auto.arima()</code> function but I can't seem to figure out if subs... | g68912 | [
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<p>As title, I am thinking of merging both into "missing data", which is to name it as NA in R. Since I don't see it will make much sense (or even any sense), to separate the "don't know" row out and to compare the information with other rows.</p>
<p>Is it OK for me to do so? Thanks!</p> | g39188 | [
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<p>I am running a multi-level model on data which is set out with one row per individual survey return, each with Individual ID and Organisational ID as columns. There are variables which can be aggregated in to group, but I first have to justify this aggregation, and believe I have to use ICC(1), ICC(2) and Rwg. Altho... | g68913 | [
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<p>Suppose I have an algorithm that classifies things into two categories. I can measure the accuracy of the algorithm on say 1000 test things -- suppose 80% of the things are classified correctly.</p>
<p>Lets suppose I modify the algorithm somehow so that 81% of things are classified correctly.</p>
<p>Can statistics... | g44008 | [
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<p>This is a discrete problem concerning integers.</p>
<p>If there are $n$ independent random variables $X_1,...,X_n$ that each take on a value from $\{1,...,x\}$ uniformly at random ($x$ distinct values), what is the probability that the minimum (call it $l$) is <em>unique</em>? The following are approaches I've tak... | g44014 | [
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<p>I want to "blow up" a sample, taken with replacement, for which I know the overall sampling probability $\pi_i$ for each item $i$. Is it valid to use bootstrapping and apply inverse probability weighting during the selection (as in the Horvitz-Thompson estimator: weight each item with $1/\pi_i$), or are there any pi... | g29142 | [
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<p>I'm doing a research module for my Computer Science degree, and for my topic, I have collected over 500,000 tweets using the Twitter Streaming API, using a ruby script to store them in a Mongo database (BSON/JSON). I started recording the tweets on Tuesday 7th Feb, and stopped the following Tuesday, so there is a we... | g68914 | [
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<p>After seeking clarification about linear model coefficients <a href="http://stats.stackexchange.com/questions/24242/how-to-apply-coefficient-term-for-factors-and-interactive-terms-in-a-linear-equa">over here</a> I have a follow up question concerning non-signficant (high p value) for coefficients of factor levels.</... | g49798 | [
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<p>I want to start working on data-mining by parsing text. It seems like the best place to start is by processing n-grams out of text to try sentiment analysis.</p>
<pre><code>Muffins are fine, I wouldn't say I like them though.
</code></pre>
<p>However, I'm curious to know if I should include punctuation or not. (I ... | g68915 | [
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<p>I have a model that is fitted with glm and I want to be able to calculate the response of this model when I specify the independent variables, while simulating the error terms. For example, if my formula is <code>y~x1*x2</code>, then this corresponds to:</p>
<p>$y_{i} = \mu + \beta_{1} x_{1i} + \beta_{2} x_{2i} + \... | g68916 | [
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<p>Is there any way to calculate variable importance in R for SVM regression and averaged neural networks?</p>
<p>I've been using <strong>caret</strong> package, that has <strong>varImp</strong> function in it</p>
<pre><code>> m <- best.tune(svm, train.x = descr[rownames(tr[[i]]),2:ncol(descr)],
train.y = tr[[... | g68917 | [
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0.02409179136157036,
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<p>I've got a non-linear model that I've been applying to some data of repeated binary outcomes. I have data for multiple years, and I'd like to add random effects (by year) for two of my parameters. Looking at the <code>lme4</code> package in R, it seems that it supports non-Gaussian error structure and nonlinear mode... | g68918 | [
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0.... |
<p>If p is the probability of success of a binomial trial i would like to calculate the number of trials n required that if performed would give a probability x of at least one success. Is there a way to obtain this n in R? I have a large vector of probabilities and would like to extract this n for a given x.</p>
<p>T... | g68919 | [
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<p>I have 14 weather stations' temperature data for the period between 2010–2013. I need to evaluate the performance of two spatial interpolation methods. I suggest to select 10 days from this period of temperature data and estimate temperature data for these days to each station and then calculate the RMSE of these da... | g68920 | [
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<p>I have trained a boosting classifier using <code>ada</code> package in <code>R</code>. Now I want to see the importance of my predictors in constructing the model. I have used <code>varplot</code> and got the following plot of variable importance </p>
<p><img src="http://i.stack.imgur.com/bgPya.png" alt="enter imag... | g68921 | [
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0.024324927479028702,
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0.08387114852666855,
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<p>Can somebody explain autocorrelation function in a time series data? Applying acf to the data, what would be the application?</p> | g68922 | [
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<p>To better ask my question, I have provided some of the outputs from both a 16 variable model (<code>fit</code>) and a 17 variable model (<code>fit2</code>) below (all predictor variables in these models are continuous, where the only difference between these models is that <code>fit</code> does not contain variable ... | g68923 | [
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<p>I am using Cox proportional hazards models for survival analysis. The specific reason I am interested in them is because they give a nice way to quantify effect size between groups via the hazard ratio, assuming the PH assumption is not violated. </p>
<p>I use R's <code>survival</code> package for the modeling. The... | g68924 | [
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... |
<p>I am trying to run a discrete duration (logistic) regression on unemployment. However, I face the following challenge:
The survey collects information on whether the person is employed or not for ten consecutive months. In addition, at the first interview those who are unemployed are also asked about their past une... | g68925 | [
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<p>I have a data.frame (<code>myData</code>) with 6 variables which are:</p>
<pre><code>Fish.species | anemone.species | substrate | Depth | Turbidity | anemone.size
</code></pre>
<p>Some of these variables are categorical (<code>Fish.species</code>, <code>Anemone.species</code>, <code>substrate</code>) and some are ... | g68926 | [
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0.0342818908393383,
-0.03184008225798607,
-0.00807248055934906,
-0.02869613841176033,
0.08316777646541595,
0.02307737246155739,
-0.020... |
<p>I am attempting to analyse downstream travel speed of fish within two different rivers, however, I am getting lost on which model I should use. Please see working below</p>
<p>data:</p>
<pre><code>data4<-structure(list(code = structure(1:32, .Label = c("10888", "10889",
"10890", "10891", "10892", "10893", "108... | g29154 | [
-0.003029931103810668,
-0.055502619594335556,
-0.0015157137531787157,
-0.0516151562333107,
0.03737402707338333,
-0.015076035633683205,
0.07110926508903503,
-0.0014106322778388858,
-0.05244280770421028,
-0.015279406681656837,
0.042088933289051056,
0.06274469941854477,
0.03783288970589638,
0... |
<p>I am running a model using <code>lm</code> in R to look at the effects of two independent factors. These independent factors are breeding group (<code>bgrp</code>: 2 levels with <code>bgrp1</code>=maternal lines; <code>bgrp2</code>=terminal lines) and sex (<code>psex</code>: 2 levels with <code>psex1</code>=males; <... | g68927 | [
-0.023352595046162605,
-0.07644093036651611,
-0.00380116980522871,
-0.017645467072725296,
0.015565887093544006,
-0.0067565347999334335,
0.021248197183012962,
-0.0011158717097714543,
-0.08477228134870529,
0.020676398649811745,
-0.016896700486540794,
0.07511822879314423,
0.03533487394452095,
... |
<p>Say I have a dataset that contains Users & all the sites that each user visited & how often each user visited it. For example:</p>
<pre><code>User1 -> (Site1, 5 times), (Site5, 3 times)
User2 -> (Site2, 10 times) & so on..
</code></pre>
<p>Now based on how may times a user visited each site, I ... | g68928 | [
-0.011425384320318699,
0.03214576095342636,
-0.0076868562027812,
-0.05972535163164139,
-0.02928117848932743,
-0.03667384758591652,
0.041627366095781326,
0.0388801135122776,
-0.08380229771137238,
-0.031232627108693123,
0.014226676896214485,
0.009835675358772278,
0.07090581208467484,
-0.0025... |
<p>Consider a study looking at the relationship of chili-pepper plant height to number of chilies produced. </p>
<p>Data was collected on all plants taller than 10cm. Initial look at the distribution of heights shows that most plants are on the short end, with a few reaching a max height of 150 cm as seen in a histogr... | g29155 | [
0.05309154838323593,
0.0367937870323658,
-0.015667658299207687,
-0.06803888082504272,
0.007667627185583115,
-0.0034300016704946756,
0.03436119109392166,
0.03550189733505249,
-0.05338943004608154,
-0.03110046684741974,
-0.011984295211732388,
0.029314791783690453,
0.03911693021655083,
-0.030... |
<p>I have a couple weekly time series and an intervention occurred over several weeks and then for some, after a period of no intervention, began again. So, the pattern is off for a period of weeks, then on for a period of weeks, then off for a period of weeks and perhaps on again.</p>
<p>The image below tries to show... | g68929 | [
-0.011924331076443195,
0.007977727800607681,
-0.001933580613695085,
-0.03887923061847687,
0.03531089425086975,
0.0015051404479891062,
0.07504136860370636,
0.057143229991197586,
0.0009649339481256902,
-0.054702360183000565,
-0.021273279562592506,
0.031169990077614784,
0.04611798748373985,
0... |
<p>I have 2 sets of variables that are weakly correlated to each other but highly correlated with third variable. Is there any method to combine these 2 variables to achieve a much more stronger correlation to third variable?
for example:
set a (correlation with b:0.2, correlation with c:0.8)
set b (correlation with a:... | g728 | [
0.037393469363451004,
-0.02310612052679062,
0.02346375584602356,
-0.048660822212696075,
0.04432069882750511,
0.018112720921635628,
-0.05560315027832985,
-0.016346093267202377,
-0.046490270644426346,
-0.02504841424524784,
0.0058236392214894295,
-0.008723119273781776,
-0.03387017175555229,
0... |
<p>anyone know about the predictive model evaluation? I'm confused about the ROC curve and confusion matrix. The area under the curve for ROC is represent about the accuracy of the classifier. But what about the confusion matrix, we can also find the accuracy. So which method is better for me to find the accuracy of th... | g29161 | [
0.02478611096739769,
-0.04775339365005493,
0.031002085655927658,
0.0011070038890466094,
0.05944877117872238,
-0.04201667755842209,
0.05469200387597084,
0.021386079490184784,
-0.028464609757065773,
-0.04375273734331131,
0.010651865042746067,
0.03579626977443695,
0.07083331048488617,
-0.0407... |
<p>I'm using several algorithms to predict a binary target. So far I tried Gradient Boosting, Random Forest, Extra Random Trees and adaboost from scikit learn.
All of these algorithms appear to predict probabilities ranging from close to zero to close to 1 with a very similar standard deviation. adaboost is the only on... | g68930 | [
0.0009664240060374141,
0.006494349800050259,
0.008223490789532661,
0.025073818862438202,
0.031156761571764946,
0.006400103215128183,
0.013426287099719048,
0.01826578937470913,
-0.015716921538114548,
-0.03721233457326889,
0.011031155474483967,
-0.027097603306174278,
0.04017261043190956,
0.0... |
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