question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I'm attempting a multiple regression model where the predicted variable is runoff ratio - the ratio of watershed discharge to the precipitation input. This should generally be bounded [0,1], however, due to measurement error some values > 1 occur.</p>
<p>Originally, I modeled this with the predicted variable un-tra... | g67562 | [
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<p>My study is to judge the appropriateness of target=1, not for predictive purpose. Can the variables occurring after target occurrence be used in regression or decision tree model? For example, a patient is admitted to ICU, he/she is likely to receive some treatments that often occur in ICU. Can I use the presence or... | g67563 | [
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<p>I am a bit confused on whether or not I have to use a fixed-effect panel time-series method or SUR (seemingly unrelated regression). To get a background of what I am trying to do, I have 10 panels of 25 weeks of data with four independent variables and one dependent variable and I am trying to find how these four in... | g67564 | [
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<p>Evan Miller's "<a href="http://www.evanmiller.org/how-not-to-sort-by-average-rating.html">How Not to Sort by Average Rating</a>" proposes using the lower bound of a confidence interval to get a sensible aggregate "score" for rated items. However, it's working with a Bernoulli model: ratings are either thumbs up or t... | g67565 | [
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<p>What is the formula for variance of product of dependent variables? </p>
<p>In the case of independent variables the formula is simple:</p>
<p>$$ {\rm var}(XY) = E(X^{2}Y^{2}) - E(XY)^{2} = {\rm var}(X){\rm var}(Y) + {\rm var}(X)E(Y)^2 + {\rm var}(Y)E(X)^2 $$
But what is the formula for correlated variables?</p>
... | g47826 | [
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<p>I am trying to solve $E\left[ E \left( \mathbf{X}|\mathbf{Z} \right) E \left( \mathbf{Y}|\mathbf{Z} \right) \right]$, (where $\mathbf{X}$, $\mathbf{Y}$, and $\mathbf{Z}$ are random variables) but I am confused - should the solution be $E \left( \mathbf{X}\mathbf{Y} \right)$ or $E\left(\mathbf{X} \right)E\left(\mathb... | g67566 | [
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<p>I have a problem embracing the benefits of labeling a model factor as random for a few reasons. To me it appears like in almost all cases the optimal solution is to treat all of the factors as fixed.</p>
<p>First, the distinction of fixed vs random is quite arbitrary. The standard explanation is that, if one is int... | g67567 | [
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<p>Take these data:</p>
<pre><code>5, 8, 9, 14
</code></pre>
<p>R says the interquartile range is <code>3</code>:</p>
<pre><code>IQR(c(5, 8, 9, 14))
# 3
</code></pre>
<p>...but I make it <code>5</code>. What am I doing wrong? Here's the steps I've taken:</p>
<ol>
<li>Find median, which is <code>8.5</code></li>
<li... | g67568 | [
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<p>I understand in theory why the Mahalanobis distance is a good measure for mutlivariate outlier detection. However, everything I tend to read warns against calculating the inverse/pseudoinverse of a covariance matrix, which is needed to compute the mahalanobis distance. </p>
<p>So, if nobody wants to compute the inv... | g67569 | [
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<p>I would like to calculate coskewness of two random variables. However I couldn't find even basic information on this matter. Is there a standard definition? How to calculate it? If not what are my alternative options? Is it possible to have a normalized coskewness like correlation coefficient? </p>
<p>Thanks </p> | g40861 | [
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<p>I have a series of wave heights observations (2observations per hour for each day in 7 months) and I'm trying to model a regression with wind data (same frequency of observation).
Since waves observations, which are my response variable, have been taken continuously trought time, I started by thinking that this one ... | g67570 | [
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<p>Choosing positives sample is a relative straightforward task, but I'm having some problem on determine what should I use for the negative example.</p>
<p>I'm working on a SVM binary classificator, trying to learn whether a pair of usernames belongs to the same individual.</p>
<p>Is obvious what to use as a positiv... | g67571 | [
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<p>I am trying to use function the <code>boot</code> function (in the R package, <code>boot</code>) and we want to change how many observations are resampled each iteration of the bootstrap.</p>
<p>If it's not possible to change the number of observations in the pseudo-sample, how many observations are used when resam... | g67572 | [
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<p>I have a 65 samples of 21-dimensional data (pasted <a href="http://pastebin.com/h8TzsZEK" rel="nofollow">here</a>) and I am constructing the covariance matrix from it. When computed in C++ I get the covariance matrix pasted <a href="http://pastebin.com/qj35dwAd" rel="nofollow">here</a>. And when computed in matlab f... | g67573 | [
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<p>Our problem: model evolution of values of a continuous variable over time. </p>
<p>I came through a paper presenting an approach for predicting the next values for a time series. Whereas ARIMA model is more accurate for long term prediction, ARTXP model is preferred to infer the next values. </p>
<p><a href="http:... | g47835 | [
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<p>Let $X_i$ be the distance between two nodes in a graph.</p>
<p>$X_i \sim \mathrm{NB}(r,p)$ where $p \sim \mathrm{Beta}(\alpha, \beta)$.</p>
<p>After the posterior hyperparameters are obtained, $\mathrm{Beta}(\alpha,\beta) – \mathrm{Beta}(\alpha’,\beta’)$ could be found which would correspond to the change in expec... | g67574 | [
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<p>I was reading a paper on Bayesian curve fitting (<a href="http://www.stat.cmu.edu/~kass/papers/bars.pdf" rel="nofollow">Dimatteo et. al. Bayesian curve-fitting with free-knot splines, 2001</a>) and came across the symbol $\bumpeq$. It is used a few times throughout the paper but never explicitly defined. After a few... | g67575 | [
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<p>Consider the following unadjusted model: $$y = 1+2x_{1} +\epsilon$$ and adjusted model (adjusted for $x_2$) $$y = 1-5x_{1}+2x_{2}+\epsilon$$</p>
<p>Why would the coefficient of $x_1$ change sign and magnitude? Wouldn't this change the interpretation?</p> | g49779 | [
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<p>Let me begin by saying that I'm not entirely sure if this is the correct forum, or if Mathematics would be more suitable. The problem I'm about to describe is statistical in nature, so I suppose it fits here.</p>
<p>I have a system $m_I$ that is either in state 1, 0 or -1. In order to determine which state it is in... | g67576 | [
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<p>Suppose that you are performing a linear regression examining the main effect $x_1$ and want to adjust for possible confounders $x_2, x_3, x_4$. Is it better to have an unadjusted model and a model adjusted for <strong>all</strong> potential confounders? Or should you also consider models adjusted for only some of t... | g27162 | [
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<p>I saw <a href="http://moz.com/blog/why-the-inbound-marketing-funnel-is-essential-whiteboard-friday" rel="nofollow">this post</a> on Moz which presented a segmented marketing funnel: <img src="http://i.stack.imgur.com/t9Y4g.gif" alt="enter image description here"></p>
<p>This kind of thing would have quite a bit of ... | g805 | [
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<p>Many clustering algorithms require globular (gaussian) clusters. Main example is k-means. If clusters are not globular, these methods can bring wrong results.</p>
<p>In social sciences, data is often clustered by these algorithms (market segmentation is very common example). My question then is whether there are so... | g67577 | [
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<p>I have a data generating process of the form:</p>
<pre><code>res1 <- rnorm(N);
res2 <- res1*0.5 + rnorm(N)
x <- z[,1]*2 + res1;
ys <- x*b + res2;
d <- (ys>0); #dummy variable
y <- d*ys;
</code></pre>
<p>(blatantly stolen from an <a href="https://stat.ethz.ch/pipermail/r-help/2006-J... | g806 | [
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<p>I have 1.5 years worth of e-commerce data (orders and revenue) for 2 countries (US and UK) with daily metrics for visits, unique visitors, and page views. I would like to model these transactions and apply the model to 1.5 years worth of visitation data (visits, unique visitors, and page views) to predict e-commerce... | g67578 | [
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<p>I am having a hard time understanding the elements of an error covariance matrix for a class. Can someone clarify?</p>
<p>First, the diagonal. The variance is $E(e_i^2) - E(e_i)^2$. $E(e_i) = 0$, so it's just $E(e_i^2)$. Ok . . . so that is the square of the actual value of $e_i$? $y_i - ŷ_i$? A non-zero num... | g67579 | [
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<p>I am writing an essay which briefly discusses linear models as well as models with fixed and random effects. I am googling since ages to find a reference which says who first introduced linear models and especially later mixed effects models. I found on wikipedia that in 1918 Ronald Fisher introduced random effects ... | g35736 | [
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<p>I am establishing a model for prediction of a binary variable (Yes/No) depending on three continuous variables ($A$,$B$,$C$). I applied logistic regression analysis for a learning dataset vith the Tanagra software, and the results were good with high prediction accuracy.</p>
<p>My question is: is it possible to get... | g67580 | [
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<p>I am doing disease classification (i.e. a person is classified as normal or abnormal) using naive Bayes and SMO classifiers. I have around 30 attributes. Out of these I need to select the most relevant attributes. I am trying to choose the best attributes using Information Gain.</p>
<p>Is this a better method? Plea... | g40910 | [
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<p>I have two questions:</p>
<ol>
<li><p>I use cross validation to select a LASSO model, does the step in which a particular variable enter, indicate its relative importance?<br>
Let's age enter in step 1 and sex enter in step 2, country enter in step 3. Can I make the claim that age is more important than sex , which... | g47852 | [
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<p>I am building a neural network. Each perceptron in the network uses a <a href="http://en.wikipedia.org/wiki/Sigmoid_function" rel="nofollow">sigmoid</a> activation function.</p>
<p>Must I normalize my inputs (which currently range form 0 to 1200)? I ask this because the sigmoid function approaches 1 as the input to... | g44908 | [
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<p>I'm going to describe a problem and I'm not sure how to best solve it. I will describe the situation. When answering please recommend a method and maybe a software library. I'm using Python for my data analysis.</p>
<p>I'm trying to figure out what makes people on time. So the input data would be a bunch of variabl... | g62 | [
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0.012159823440015316,
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0.0003650819999165833,... |
<p>So I am having a problem specifying my model in OpenBUGS. A set of vectors in a linear regression model is given a multivariate normal prior with a constant mean vector and a constant precision matrix which is multiplied by a parameter with a hyperprior of a gamma distribution.</p>
<p>The code is as follows:</p>
<... | g45909 | [
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0.012294068932533264,
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... |
<p>I am simulating the effect of certain conditions on estimates obtained using OLS regression. In running 100 replications I get 100 sets of standard errors for the regression coefficients. How do I calculate the standard error of the estimates? Is it simply the standard deviation of the estimated standard errors f... | g67581 | [
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<p>What's the best way to study the association between nominal response (3 non-ordered categories) and one ordinal predictor variable (most observations are interval scaled, but some are censored (only known to be above x)) in smallish sample (50).</p>
<p>I think that Mantel-Haenszel row means score test (SAS) might ... | g67582 | [
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0.... |
<p>I'm dealing with a supervized binary classification issue. My dataset is composed of 1500 individuals, living in 600 households. I have approximately 4000 variables to classify my subjects as "infected/uninfected". </p>
<p>I was wondering how would it be possible to account for the hierarchical nature of my data in... | g67583 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/28873/goodness-of-fit-test-for-a-mixture-in-r">Goodness of fit test for a mixture in R</a> </p>
</blockquote>
<p>I just estimated the parameters for a mixture of two gaussians with different means and diff... | g49614 | [
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<p>I have adjusted the parameters (lambda, mu, sigma) for a mixture of two normals fitted to my data. Now I would like to plot the cdf of this model using the explicit function instead of the ecdf. Is there any way to do this or I do I have to simulate data so then I can use again ecdf?</p>
<p>The explicit function is... | g47868 | [
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0.... |
<p>I am writing a program to predict the click through rates of online ads. Two important notes about this problem:</p>
<ul>
<li><p>click through rates are very small (like 0.1%)</p></li>
<li><p>click through rates depend on several parameters (like size of the ad, country in which ad is shown, whether the user has se... | g67584 | [
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0.0... |
<p>I'm trying to minimize a custom function. It should accept five parameters and the data set and do all sorts of calculations, producing a single number as an output. I want to find a combination of five input parameters which yields smallest output of my function.</p> | g67585 | [
0.04778432473540306,
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0.007902815006673336,
0.0203... |
<p>How do I establish the +/- in terms of a set of mean ages. My mean age is 27.2. The ages are 20 23 24 43 22 26 18 32 18 41 22 20 26 46 21 27 19 19 39 40 19 39 18 38 24 24 23 30.</p>
<p>Thank you. </p> | g41043 | [
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0.03421969339251518,
0.029594089835882187,
0... |
<p>What is the best imputation method for a dataset consisting of stochastic data? For example, let's say you have a table of security returns. In some cases the missings are random, in other cases are not. For example, a new IPO would have a relatively short time-series.</p>
<p>Suggestions:</p>
<ul>
<li>Expectations... | g67586 | [
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0.012739141471683979,
0.003531879745423794,
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0.011402408592402935,
0.04678884148597717,
0.021968316286802292,
0.006362936459481716,
0.0... |
<p>I have 10 years of backtested simulated performance of some trading strategy (using historical prices), and N months of actual trading performance. What statistical test can I do find out if I'm on target with the backtesting numbers? (both, in terms of expected annual returns and expected annual Sharpe ratio)</p> | g67587 | [
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0.032336488366127014,
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... |
<p>I have the following setup. </p>
<ul>
<li>Parameters $W$ with density $\pi(w)$.</li>
<li>Observed data $X_1,...,X_n$ iid.</li>
<li>Density of $X_i|W=w$ is $f(x_i|w) = \int_{\Delta(x_i)} f(\mathbf c|w) \,d\mathbf c$.</li>
<li>The simplex $\Delta(x_i) = \{\mathbf c \geq 0 : c_1 + \cdots + c_m = x_i\}$.</li>
</ul>
<p... | g67588 | [
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0.01057261973619461,
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0.009560435079038143,
0.07116740196943283,
0.0... |
<p>I have a dataset that's nominally 16-dimensional. I have about 100 samples in one case and about 20,000 in another. Based on various exploratory analyses I've conducted using PCA and heat maps, I'm convinced that the true dimensionality (i.e. the number of dimensions needed to capture most of the "signal") is arou... | g27184 | [
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-0.005456097424030304,
0.06363549083471298,
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0.08920567482709885,
... |
<p>I have two dataset that i want to compare.
each dataset contain the weight of 10 different person measured for 3 different day.</p>
<p>I am interested in measuring the probabily that the two sample originate from the same population.</p>
<p>People seem to suggest doing a Kolmogorov-Smirnov test but i need a measu... | g67589 | [
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-0.007546784356236458,
0.04197719320654869,
-0.051780495792627335,
0.07815821468830109,
0.0202... |
<p>I have a linear string of unit length, and I randomly sample two locations a and b from Uniform(0, 1). Then I cut the string at these two locations to get a sub-string. What is the distribution for the size of the sub-string (i.e. |a-b|)? Otherwise, I want to at least know the mean and variance.</p> | g67590 | [
0.009198120795190334,
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0.0014524548314511776,
-0.03210356831550598,
-0.021707948297262192,
0.031897109001874924,
-0.019015148282051086... |
<p>I am trying to replicate a Stata manual example (-mlogit-) of nested
logit estimation,</p>
<pre><code>webuse restaurant
nlogitgen type = restaurant(fast: Freebirds | MamasPizza, family: ///
CafeEccell | LosNortenos | WingsNmore, fancy: Christophers | MadCows)
nlogittree restaurant type, choice(chosen)
nlogit chos... | g67591 | [
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0.006119327619671822,
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0.042883023619651794,
0.07278572022914886,
0.... |
<p>I'm choosing a GAM, and when I try to do</p>
<pre><code>anova(model.1, model.2, test="F")
</code></pre>
<p>It gives me a warning message saying that the F test is inappropriate for binary outcomes. Why is this?</p>
<p>I get virtually the same p-value either way.</p> | g67592 | [
-0.006290921475738287,
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0.0012880360009148717,
0.048509616404771805,
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0.03... |
<p>I am doing Rainfall-Runoff modeling. I have 4014 inputs and 4014 outputs. I am confused about the of support vectors. Suppose I have a model having 2000 support vectors and I have another model having 3900 support vectors. Both perform well, and the second model has slightly better performance. Which is better? Wha... | g67593 | [
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0.0037694296333938837,
0.005940907634794712... |
<p>I have estimated the coefficients of the following equation, using the fixed-effect model:</p>
<p>$Y_{it}=\alpha _i+ \rho _t + \beta _1 X_{it}+\beta _2 C_i*D_t+\epsilon_{it}$</p>
<p>I have observations from 1980 to 2010 for $Y_{it}$ and $X_{it}$.I am interested in the interaction term. The dummy variable $D_t$ is ... | g67594 | [
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0.0050076949410140514,
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0.07260802388191223,
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<p>I have a strange problem that I'm not sure how to solve:</p>
<p>I have complex data points in a time series. The amplitude of these complex numbers in the time series forms a straight line, which I have fit for. But now what I want to do is <em>subtract</em> this fit from the data points. Except I have no idea how ... | g67595 | [
0.0602131262421608,
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0.01623028889298439,
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0.00615435978397727,
0.052465442568063736,
-0... |
<p>Assume I have two factors A and B potentially predicting my outcome Y. Now I would like to test for fixed-effects using likelihood ratio test to find the best model.</p>
<pre><code>fm1 <- lmer(Y~1+A*B+(1|subject))
fm2 <- lmer(Y~1+A+B+(1|subject))
fm3 <- lmer(Y~1+A+(1|subject))
fm4 <- lmer(Y~1+B+(1|subje... | g67596 | [
0.02428615838289261,
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0.008298923261463642,
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0.012298027984797955,
0.043... |
<p>We did customer survey in last fall from which we know how different stratas answer to survey questions. We did notice that amongst many strata having younger people who move often the non-response rate was much higher than amongst more established of our customers. </p>
<p>Original survey was based on simple rand... | g67597 | [
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0.04816214740276337,
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0... |
<p>I have three independent variables (all binary) and two interaction variables that I would like to test for their effect on the dependent variable "Awareness_level". This dependent variable is also binary.</p>
<p>I assigned participants randomly to one of 8 different conditions. In the assigned condition they were ... | g67598 | [
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0.051437512040138245,
0.024058911949396133,
0.012344455346465... |
<p>I'm trying to work out the effect of treatment on a group using a counterfactual approach. However, I don't know how I can infer the treatment start date for the comparison group. </p>
<p>For both groups I have a time point from which on they are eligible for treatment. I'm using kernel matching to match both group... | g27195 | [
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0.027045872062444687,
0.02800813876092434,
0.029155060648918152,
0.02439858391880989,
0.032... |
<p>I have been handed a dataset with many poor variables and what appear to be outliers.</p>
<p>Looking at histograms and box plots of the distributions, many cannot even form a box plot due to the distribution.
Some of the distributions are just plain terrible with a chunk of single numbers and a second chunk of sing... | g27196 | [
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0.03510938584804535,
0.03902348503470421,
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0.0161... |
<p>After going through some slightly terse mathematics, I think I have a slight intuition of kernel density estimation. But I am also aware that estimating multivariate density for more than three variables might not be a good idea, in terms of the statistical properties of its estimators.</p>
<p>So, in what sorts of ... | g67599 | [
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0.029628820717334747,
0.026397529989480972,
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0... |
<p>Package RHmm (R)</p>
<p>I have a vector which I fit into a hmm model in an attempt to select an optimal number of states for a hidden markov model. </p>
<pre><code>x<-c(-0.0961421466,-0.0375458485,0.0681121271,0.0259201028,0.0016780785,0.0311860542,
0.0067940299,0.0126520055,0.0357599812,0.0007679569,0.04... | g67600 | [
0.006099258083850145,
-0.03934577852487564,
0.021681377664208412,
0.02912113070487976,
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0.06341665238142014,
0.03959418088197708,
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-0.03390827029943466,
-0.04347312077879906,
0.012328483164310455,
0.053968075662851334,
0.009... |
<p>Is there someone who knows an econmetric model to describe count datas with an upper bound? Thank you! </p> | g67601 | [
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<p>In practical application, I have witnessed often the following practice. One observes a pair $(x_t, y_t)$ over time. Under the assumption that they are linearly related, we regress one against the other using geometric weights rather than uniform ones, i.e., the OLS minimizes
$$\sum_{t=0}^\infty k^{t} (y_{T-t}- a ... | g67602 | [
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-0.025067349895834923,
0.028105726465582848,
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0.08970044553279877,
0.... |
<p>In R, what is the difference between:</p>
<pre><code>if(x>2 & x<3) ...
</code></pre>
<p>and</p>
<pre><code>if(x>2 && x<3) ...
</code></pre>
<p>Similarly:</p>
<pre><code>if(x<2 | x>3) ...
</code></pre>
<p>and</p>
<pre><code>if(x<2 || x>3) ...
</code></pre> | g47894 | [
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0.007964213378727436,
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0.014173437841236591,
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0.015897255390882492,
-0.... |
<p>I'm just having a look through Hadley's very excellent book about his ggplot2 R package. </p>
<p>He has some code to remove a linear trend in the diamonds dataset, like so:</p>
<pre><code>d <- subset(diamonds, carat < 2.5 & rbinom(nrow(diamonds), 1, 0.2) == 1)
d$lcarat <- log10(d$carat)
d$lprice <-... | g27202 | [
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<p>I have a question on testing mortality table.
Suppose I am given a simple mortality table:</p>
<pre><code>age | prob of dying | prob of surviving
---------------------------------------
20 | 0.01 | 0.99
21 | 0.02 | 0.98
22 | 0.03 | 0.97
23 | 0.04 | 0.96
...... | g52 | [
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<p>I am of the knowledge that to test whether a data set approximates a normal distribution, the median and the mean should be approximately equal. So my question is to what degree should the difference between the median and the mean be accepted? </p> | g67603 | [
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<p>I'm dealing with a time series data and I'm trying to construct a time series model for this particular dataset. I'm new to R and tried using the the <code>auto.arima</code> function under the forecast package:</p>
<pre><code>fit <- auto.arima(tsdata, xreg=cbind(CSS2$Month,CSS2$DayID,CSS2$Year),
... | g67604 | [
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<p>I suspect this question is really about basic definition, but I could not find the ressource I need to solve my problem.</p>
<p>I want to understand why the pearson $\chi^2$ test statistic, and corresponding residuals, are computed the way they are in R.</p>
<p>First, some tests:</p>
<pre><code>>d<-data.fra... | g67605 | [
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<p>My Error's plot from a linear regression</p>
<p><img src="http://i.stack.imgur.com/bprYB.png" alt="enter image description here">.</p>
<p>Is it Normal distributted? If not, why? What that negative big bar means?</p>
<p>The code used is:</p>
<pre><code> library(MASS)
sresid <- studres(reg3)
hist(sresid, freq... | g67606 | [
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<p>I need to compare my observed point vs random points that have been constrained to be relevant to that observation. In my case, I am looking at habitat selection along transects of animal movements. I have several types of variables categorical and continuous. Here is an example of 1 of my many models:</p>
<pre><... | g67607 | [
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<p>In my thesis I'm trying to discover which factors influence the CSR (corporate social responsibility, <code>GSE_RAW</code>) behavior of companies. Two groups of possible factors / variables have been identified: company-specific and country-specific.</p>
<p>First, company-specific variables are (among others)</p>
... | g67608 | [
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<p>I have a dataset $X = \{x_1, ..., x_n\}$. I also have three algorithms, $A_1, A_2, A_3$, that each take a single data point as input and produce some measure of how well they performed. If I apply each of the algorithms to each of the data, I get a matrix of performance measures, $M$, where $M_{a,i}$ is the value of... | g47899 | [
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<p>The data I have is based on percentages. I have several variables on percent of children that have been immunized. So one column that is one kind of immunization, and is ordered by state. So for example in my data it shows that in Massachusetts, 53.3% of children have gotten the HPV4 vaccine. I want to correlate the... | g67609 | [
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<p>I came across this image in a blog post <a href="http://www.statisticsblog.com/2013/04/sudden-clarity-about-the-null-hypothesis/" rel="nofollow">here</a>.</p>
<p><img src="http://i.stack.imgur.com/n2EuU.jpg" alt="enter image description here"></p>
<p>I was disappointed that reading the statement did not illicit th... | g27208 | [
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<p>I am trying to find the best way to visualize different distributions of accuracy. Accuracy here is a value in the interval [0,1], 0 meaning not accurate, 1 maximum accuracy.</p>
<p>I have different methods to compare, so I decided to use violin plots.</p>
<p><img src="http://i.stack.imgur.com/AaZaE.png" alt="accu... | g19921 | [
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<p>Are the values of <code>xcorr(x,y)</code> in MATLAB correlation values or not? I'm asking this because in MATLAB <code>xcorr(x,y,'coeff')</code> normalizes values. Is it normalizing covariance values to get correlations? </p>
<p>I'm confused if cross correlation values are necessarily between -1 and 1 like Pearson ... | g67610 | [
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<p>I am working on a classification problem, which may contains a unknown number of data classes, typically 5-50 classes in each sample. I had several classification algorithms, each gives me a classification output based on a given sample. However, these classification outputs are almost unlikely to agree with each ot... | g67611 | [
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<p>Here I am working on fingerprint recognition. I am using SVM for fingerprint feature verification and classification. I want to classify fingerprint images using two class problem of SVM that means in one class I want right loop, left loop and tented arch type images and in another class I want arch type and whorl t... | g27209 | [
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<p>I want to study some data describing $k$ different systems. For a given system, these data can take two forms:</p>
<ul>
<li><em>Global</em> metric: a single value describing the whole system.</li>
<li><em>Local</em> metric: a series of values describing each element in the system. This is <em>not</em> a temporal se... | g27210 | [
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<p>The problem I have is one that ideally seems to be suitable by considering it as a multivariate normal pdf problem however this way seems impossible.</p>
<p>Consider three Normal distributions </p>
<p>$X\sim N(\mu_{x},\sigma_{x})$,</p>
<p>$ Y\sim N(\mu_{y},\sigma_{y})$, </p>
<p>$Z\sim N(\mu_{z},\sigma_{z})$.</p>... | g27213 | [
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<p>I have read about <a href="http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1225&context=usgsnpwrc">controversies regarding hypothesis testing</a> with some commentators suggesting that hypothesis testing should not be used. Some commentators suggest that <em>confidence intervals</em> should be used in... | g49634 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/16287/assessing-error-of-a-spatial-interpolation-algorithm">Assessing error of a spatial interpolation algorithm</a> </p>
</blockquote>
<p>This is a similar question to <a href="http://stats.stackexchange.... | g49780 | [
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<p>Assuming n testers were independently testing the same application for a given period. Each tester found a given set of bugs (Some of the bugs were detected by more than one tester).</p>
<p>For example:</p>
<p>Tester 1 found bugs {1,2,3,4,5} Tester 2 found bugs {3,5,6,7} Tester 3 found bugs {1,3,5,8,9,10}</p>
<p>... | g67612 | [
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<p>I have thousands of product info in a database with category, title, description, make, model, price and store name. I have grouped those products by store names and it seem to span to 4 stores. So thousands of products in those 4 stores.</p>
<p>I want to compare every store's product with rest of stores' products ... | g67613 | [
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<p>I have a sequence of bytes. My null hypothesis is that each byte is drawn independently from a uniform distribution. What is the correct statistical tool for testing such a hypothesis?</p>
<p>My first thought was Pearson's chi-squared test. However... apparently that only works reliably when the expected frequencie... | g49380 | [
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<p>I know this is a very debated topic, even on this site, but I still couldn't find an answer to my problem. </p>
<p>Recently I am working with large samples (300, 400 and more). For now, I am trying to use simple techniques, such as correlation, T-tests, and ANOVA, all of which require the normality assumption (fro... | g67614 | [
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<p>I tried finding an answer to this question on this and other sites but to no avail - if I am missing something please excuse my inability to locate the answer!</p>
<p>Basically I have several dependent variables (<code>dv</code>) for two land management treatments (<code>treat</code>) measured quarterly (<code>seas... | g67615 | [
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<p>In my PhD thesis I am working on spatial modeling of different chemical parameters in groundwater, and for spatial modeling I am also using the multiple statistical approach.
I have a question about multiple regression analysis. (Or it is better to use polynomial regression?)</p>
<p>The equation for spatial regress... | g67616 | [
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<p>Can one just fit a linear model between $Y$ and $X$, and then take the p-values of the $t$-test done on the slope (or beta) of the linear model? Since presumably correlation would be in the same direction as the slope/beta of the linear regression model?</p> | g27223 | [
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<p>Normally we cannot draw an ROC curve for the discrete classifiers like decision trees.
Am I right?
Is there any way to draw an ROC curve for Dtrees?</p> | g67617 | [
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<p>I have one group of six raters who scored recordings of two separate six-person groups of participants, each group under separate conditions. While the participants were divided into two independent groups, the ordinal data came from the same group of raters. Due to the small sample size (i.e. 12 ordinal scores to... | g27224 | [
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<p>I measured two variables (outcomes) $Y_a$ and $Y_b$ for several subjects. $Y_a$ and $Y_b$ are continuous variables defined on $[0,100]$ and have a bimodal distribution. I tried using a transformation but came up with nothing worthy. I have two independent variables $X_1$ (factor with 2 levels) and $X_2$ (factor wit... | g67618 | [
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<p>Suppose we have two distributions: $\mu$ and $\upsilon$ on $\{1,2,3\}$. $\mu(1) = 1/2, \mu(2) = 1/3, \mu(3) = 1/6,\upsilon(1) = 1/3, \upsilon(2) = 1/6, \upsilon(3) = 1/2$. Could anyone explain me (as simple as possible since I'm at a beginner level in stats) how I can compute the total variation distance of $\mu$ an... | g27225 | [
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0.013235235586762428,
... |
<p>I am working on severely imbalanced data. In literature, several methods are used to re-balance the data using re-sampling (over- or under-sampling). Two good approaches are:</p>
<ul>
<li><p>SMOTE: Synthetic Minority Over-sampling TEchnique (<a href="http://www.csee.usf.edu/~hall/papers/smote.pdf" rel="nofollow">SM... | g67619 | [
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0.02181447669863701,
0.008968556299805641,
0.01887633465230465,
0.024394871667027473,
0... |
<p>I'm reading a paper that mentioned the term: ad-hoc classifiers. I look into the web but couldn't find an answer. I wish someone could help.</p> | g12591 | [
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0.03490808606147766,
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0.08833151310682297,
0.06836496293544769,
0.0... |
<p>I have a very large data set which I would like to summarise in as small a space as possible, preferably one side of A4.</p>
<p>The data are from a customer satisfaction survey and are Likert-type scales, 5 scales for each work area, with 190 work areas in total. I would also like to represent the response rate on ... | g67620 | [
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-0.01712479256093502,
0.07335668057203293,
-0.006176842842251062,
0.0730227380990982,
0.0288379... |
<p>Suppose I have an $ARIMA(p,d,q)$ model:</p>
<p>$ \left(1 - \sum_{i=1}^p \alpha_i B^i \right) \nabla^d X_n = \left(1 + \sum_{i=1}^q \beta_i B^i\right)\epsilon_n$</p>
<p>where $B$ is the shift operator (or lag operator), $\nabla$ is the backward difference operator and $\{\epsilon_n\}_{n=0}^\infty$ is a white noise... | g67621 | [
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0.07002842426300049,
0.05... |
<p>Assume we have three hypotheses: $$A\equiv\text{we have a box with 1/3 defective}\\B\equiv\text{we have a box with 1/6 defective}\\C\equiv\text{we have a box with 99/100 defective}$$
given the prior information $X$, we take: $$P(A|X)=\frac{1}{11}(1-10^{-6})\\P(B|X)=\frac{10}{11}(1-10^{-6})\\P(C|X)=10^{-6}$$
The thre... | g67622 | [
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-0.0365133099257946,
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0.05852469056844711,
-0.03... |
<p>Assume we're polling or surveying people about their predictions regarding some future event. This survey is done every day, and the event they are asked to predict is the same every time. For example, each morning they are asked "Do you think it will be sunny this afternoon?" Assume for the purposes of this questio... | g27230 | [
0.013192843645811081,
-0.04519297927618027,
0.004820443689823151,
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0... |
<p>If I understood it correctly, the Metropolis-Hastings algorithm allows one to sample from a distribution without an analytical representation, which comes in handy, for instance in the Bayesian statistics literature.</p>
<p>Quite generally, the algorithm seems to work as follows (this is similar to <a href="http://... | g67623 | [
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0.048277679830789566,
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0.045539069920778275,
0.08117654919624329,
0.00955... |
<p>I am looking for some source of information, some articles about Robust ANCOVA. Can you suggest me something? And do you know any source that directly gives information about how to perform various robust ANCOVA with R?</p>
<p>I have seen a citation about Maxwell et al. 1993, an article called <em>Analysis of Covar... | g67624 | [
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0.04140710458159447,
-0.0039... |
<p>I don't have a very strong background in statistics so I have a few conceptual questions and there is a strong possibility I'm missing something obvious.</p>
<p>Suppose I'm interested in estimating the 99th percentile of body weight in the United States and I have data from every town in every state. I could simply... | g11371 | [
0.03257166966795921,
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0.002789277583360672,
0.01630425453186035,
... |
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