question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I have a collection of data, which I originally thought was normally distributed. Then I actually looked at it, and realised it wasn't, mostly because the data is skewed, and I also did a shapiro-wilks test.</p>
<p>I'd still like to analyse it using statistical methods, and so I'd like to hypothesis test for skew-n... | g38762 | [
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<p>Let's say I give you a 10-sided die and tell you that it is biased in some way. I then let you roll the die 5 times and you observe, let's say, 8, 8, 8, 2, and 8. Lastly, I ask you what your belief is regarding how the die is biased. </p>
<p>How would you use Bayes' Theorem in this situation to go from complete ign... | g62549 | [
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<p>I'm trying to understand some concepts related to predictive modeling. So let's say that I have the following data sample and am trying to regress <code>sales</code> on <code>clicks</code> and <code>calls</code>. Ultimately, I'm interested in predicting sales figures for any given month (e.g., <code>Jan</code>, <cod... | g62550 | [
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<p>I have 168 rows of patient data: 104 controls and 64 cases. I want to know if albumin status (low or high) is related to case/control status. I made a table using R:</p>
<pre><code>> table(Albumin, Status, useNA = "ifany")
Albumin Control Case
Low 51 16
High 39 32
<NA> 14... | g38765 | [
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<p>I am interested in modeling the following experiment:</p>
<p>A binomial trial with $n$ Bernoulli experiments is run.
For the k positive outcomes a second (independent) binomial trial with $k$ runs with a <strong>different</strong> success probability is run.</p>
<p>For example: I throw $n$ darts with probability $... | g62551 | [
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<p>I am about to start out analysis of a microbiological data set (ETEC: enterotoxic <em>echerichia coli</em> in children with diarrhea). The variables refer to the ETEC, not to the children. Some of the variables, like colonization factors (CF), may have none, one or multiple values; thus CF becomes a multiple-valued... | g62552 | [
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<p>The first method to test for the day of the week effect is OLS regression. This method has been used by many empirical researchers testing for a day of the week effect.</p>
<p><img src="http://i.stack.imgur.com/O2uyL.png" alt="enter image description here"></p>
<p><img src="http://i.stack.imgur.com/7hv8t.png" alt=... | g62553 | [
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<p>I'm currently trying to play around with NLTK and scikits-learn for text clustering news articles.</p>
<p>How do I extend the models to add the scaling of features from a document (I'm doing some preprocessing on the text articles) so I can experiment by weighting ?</p>
<p>I'm starting from this outline of docume... | g62554 | [
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<p>A colleague discussed about a concept of <em>similarity</em> between two different entities <em>line</em> and <em>a set of points</em>. My first guess for solution was considering distances squared ($d^2$) as in LS. So for the following demonstration in which the black line is fitted by means of Least Squares method... | g62555 | [
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<p>I have 4 dependent categorical variables and 11 independent <code>variables.im</code> not been able to write the commands in R using the CRAN's mvtnorm. </p>
<p>Can anyone help me with that?</p> | g19694 | [
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<p>I've been asked by a reviewer on a manuscript to provide plots of a model fit for a binomial lme which is specified as follows:</p>
<pre><code>EVENT_OCCURRED ~ (IV1*IV2) + IV3 + (1|PPT) + (1|RANDOM1) + (1|RANDOM2) + (1|RANDOM3)
</code></pre>
<p>Where <code>EVENT_OCCURRED</code> is a binary value (0/1), <code>IV1</... | g62556 | [
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<p>I have read that the distribution for the random effects estimator in lme4 is highly skewed and for this reason standard errors are not reported. I wonder if anyone can provide a reference for this ? I have access to the book by Bates and Pinherio, but not Raudenbush and Bryk. A published paper would also be fine. T... | g38770 | [
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<p>Consider the simple regression model $y=\beta_0+\beta_1x+u$, where $corr(x,u)=1$ and all random variables have normal distribution. Is it possible to provide asymptotically consistent estimate for $\beta_1$?</p>
<p>Since $corr(x,u)=1$, we can write $u=ax+b$ and substitute it to get $y=\beta_0+b+(\beta_1+a)x$. So o... | g37475 | [
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<p>Let there be two samples of size $n$, $x_i$ and $y_i$ from two different normal distributions.</p>
<p>What is $\operatorname{cov}(\bar X_n, \bar Y_n)$? And how can it be estimated?</p>
<p>The motivation for my question is to understand if there is a way to know if two paired samples are correlated in such away so ... | g62557 | [
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<p>I'm using the analytical strategy of Christakis and Fowler to study the spread of behaviors in social networks. Page 566 of this article reviews their method in more details: <a href="http://humannaturelab.net/wp-content/themes/human-nature-lab/media/pdf/publications/articles/SIM_special.pdf" rel="nofollow">http://h... | g62558 | [
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<p>I am curious, given a data set that has a design with two within subjects factors, which plots would work the best to generalize the the observations?</p> | g62559 | [
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<p>So I know we statisticians don't use differential equations as heavily as e.g. engineers. Actually, I have never seen or needed them in my studies.</p>
<p>I'm curious to learn about them now, and I'd be especially happy to hear about statistical applications for DEs. This would make me even morew motivated to learn... | g19698 | [
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<p>Suppose you are given a binary classification problem. How do you know that you have to map the problem into a higher dimensional space? In other words, how would you know that a linear SVM is not suitable for a problem? Would you look at the accuracy?</p> | g62560 | [
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<p>Is it appropriate to apply predictive modeling variable selection and shrinkage techniques (for example, ridge regression or lasso) for <em>in-sample</em> prediction rather than out-of-sample prediction? Perhaps using 5- or 10-fold cross validation?</p>
<p>I think this would boil down to using a ridge regression or... | g19701 | [
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<p>I am new to regression and having problem in solving Heteroscedasticity in OLS. Have done lots of homework and test before seeking your advice. Sharing the background and what I have done to solve the problem. Hope you can share your thoughts if my approach was correct.</p>
<p><strong>Objectives:</strong></p>
<ol>... | g19702 | [
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<p><em>Most of this is background, skip to the end if you already know enough about Dirichlet process mixtures</em>. Suppose I am modeling some data as coming from a mixture of Dirichlet processes, i.e. let $F \sim \mathcal D(\alpha H)$ and conditional on $F$ assume $$Y_i \stackrel {iid}{\sim} \int f(y | \theta) F(d\th... | g62561 | [
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<p>I can see lots of paper mentioning they selected some parameters like regularization parameter $\lambda$ by cross validation. What do they mean by that?</p> | g19703 | [
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<p>Let X1, X2, ..., Xk be an i.i.d. sample of a random variable X. I plot these in a histogram and would like to include a confidence interval for the height of each histogram bar. Do you know how to go about doing it?</p> | g49689 | [
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<p>Say I have a number of time series, e.g. a number of temperature records from various stations in a region. I want to get a single temperature record for the whole region with which I could describe aspects of the regional climate. The intuitive approach might be to simply take the average of all stations at each ti... | g19705 | [
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<p>Lets say I run an experiment testing accuracy of hitting targets of two different sizes. I have 10 participants and 40 targets, 15 small and 25 large. I then have the number of misses for each target recorded.</p>
<p>So I end up with 150 small target scores and 250 large target scores. I want to see if there is a d... | g62562 | [
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<p>For an applied economics paper, I am looking for a 2-parameter probability distribution function that has the following properties:</p>
<ul>
<li><p>Simple, closed-form PDF $f(x)$ and CDF $F(x)$, defined on the interval $[0, M]$ (where $M$ may be infinite).</p></li>
<li><p>$f(x)$ is bell-shaped, in the sense that it... | g34483 | [
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<p>How would you explain intuitively what is a unit root, in the context of the unit root test? </p>
<p>I'm thinking in ways of explaining much like I've founded in <a href="http://stats.stackexchange.com/questions/17537/understanding-variance-intuitively">this question</a>.</p>
<p>The case with unit root is that I k... | g62563 | [
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<p>Thanks in advanced for the help:</p>
<p>I have a continuous dependent variable $y$ and two independent categorical variables $x_1$ and $x_2$. As well, they have been sampled from different sites (site).</p>
<p>$x_1$ has 3 levels
$x_2$ has 5 levels</p>
<p>is it correct to do:</p>
<pre><code>dat <- aov(y ~ x1... | g62564 | [
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<p>I have a group of samples drawn from density function $p(x,y)$, so it has the marginal density $p(x)$ and $p(y)$, and conditional density $p(x|y)$ and $p(y|x)$. </p>
<p>In what way I can construct another group of samples, with the SAME $p(x,y)$ but the $p(x)$, $p(y)$, $p(x|y)$ and $p(y|x)$ are changed?</p> | g19708 | [
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<p>Assume there are 2000 students, $m$ boys and the rest are girl. Now we take a sample of 5 students which contains only 1 boy. We claim that there are more girls than boys in the population. So what we want to do is to check the maximum likelihood under $H_1$ $H_0$, but the problem is I don't know how to get the maxi... | g604 | [
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<p>Suppose that $w_1,w_2,\ldots,w_n$ and $x_1,x_2,...,x_n$ are each drawn <em>i.i.d.</em> from some distributions, with $w_i$ independent of $x_i$. The $w_i$ are strictly positive. You observe all the $w_i$, but not the $x_i$; rather you observe $\sum_i x_i w_i$. I am interested in estimating $\operatorname{E}\left[x\r... | g62565 | [
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-0.017663605511188507,
-0.053293514996767044,
-0.03468545153737068,
0.059070270508527756,
0.0028721403796225786,
-0.037660472095012665,
0.01245158165693283,
0.005513849668204784,
0.023652497678995132,
0.03518892079591751,
0.... |
<p>I have constructed a social capital index using PCA technique. This index comprises values both positive and negative. I want to transform / convert this index to 0-100 scale to make it easy to interpret. Please suggest me an easiest way to do so. </p> | g19709 | [
-0.0016110852593556046,
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0.02501554787158966,
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0.04650966450572014,
... |
<p>I would like to compare multiple means using a method such as an ANOVA. This would have to be followed up with either Scheffe's test or the Games-Howell post-hoc method (my data is non-normal - to different degrees and can't all be transformed to normality using the same transformation - heteroscedastic and has grea... | g62566 | [
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0.004667552653700113,
... |
<h2>PROBLEM</h2>
<p>Suppose I have four dice: red (R), green (G), blue (B) and yellow (Y). I throw these dice several times. Each throw uses two of the four dice, and only the following pairs are allowed:</p>
<ul>
<li>RB</li>
<li>RY</li>
<li>GB</li>
<li>GY </li>
</ul>
<p>After each throw I note which dies rolled a '... | g19710 | [
-0.00662192003801465,
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... |
<p>Combining binary classifiers, I want to solve multi-class classification problem in the following setting.
Suppose there is a dataset and each data is in one of four classes: A1, A2, B1 and B2. A1 and A2 are somehow similar. B1 and B2 are also somehow similar.
(e.g. A1=rose, A2=iris, B1=cow, B2=horse)</p>
<p>Intuit... | g19711 | [
0.071022629737854,
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0.02365862764418125,
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0.01241... |
<p>I am using categorical variable (having three categories) as independent variable in model and found that one category is coming to be significant while another category is not coming to be significant while variable is significant at overall level to be included in model. I am not able to understand whether I shoul... | g62567 | [
-0.037066709250211716,
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0.026440678164362907,
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<p>I have morphological data from two different determined groups (<code>It</code> and <code>Nd</code>), where the variables are heterogeneous (continuous, semi-qualitative, binomial). I want to know if the groups differ morphologically and if so, which variables account most for the difference between them. </p>
<p>F... | g62568 | [
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0.017170488834381104,
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0.... |
<p>I am working on biological dataset. Around 20000 genes of each sample are comparing with the same ones in another group in order to find significantly differentially expressed genes. I am comparing 3 different factors in 12 sample groups (3 replicates for each type). I think because of fewer amounts of replicates I ... | g19712 | [
-0.01817312464118004,
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0.01... |
<p>I have been trying to understand the representation of the joint probability density of Markov random fields in the form of factors of the potential functions. I am finding it difficult to grasp the idea of potential functions and how we are supposed to choose a potential function. Any suggestions on how I should ge... | g62569 | [
0.006622514221817255,
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0.007825681939721107,
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0.04743655398488045,
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<p>I'm comparing matched data from a series of patients, looking at the effect of mental stress on cardiac conduction. I'm using the loess function to visually describe my data, and have 2 curves: one for with and one for without mental stress. I'd like to compare these curves. </p>
<p>Is it possible to compare two lo... | g19715 | [
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<p>I am looking for the (or a) suitable name of a continuous univariate
distribution depending on two parameters $\alpha>0$ (shape) and $\beta
>0$ (scale). The support is $(0, \,\beta)$ and the survival and density
functions are
$$
S_X(x) = \left[1- x/\beta\right]^\alpha \qquad f_X(x) = \frac{\alpha}{\beta}\, ... | g62570 | [
0.03794195502996445,
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0.035846009850502014,
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-0.0... |
<p>I am asked to perform a regression on a dependent variable that only takes positive value. Intuitively one can think of Poisson or negative binomial, but unfortunately the response variable that I am dealing with is not a count variable. How can I perform a regression on such response variable? any ideas?</p>
<p>th... | g62571 | [
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0.006853995379060507,
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<p>I want to analyze data from TIMSS on mathematics. Data contains two data sets one for student level information (i.e. level-1) and another one for school level information (i.e. level-2). Data sets are provided in two different files and each file contains school ID variable.</p>
<p>As far as I know, I can't do mul... | g62572 | [
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0.017620498314499855,
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0.03630761057138443,
-... |
<p>The current question is inspired by this one:
<a href="http://stats.stackexchange.com/questions/13797/which-one-is-the-null-hypothesis-conflict-between-science-theory-logic-and-sta">Which one is the null hypothesis? Conflict between science theory, logic and statistics?</a></p>
<p>Paul Meehl attributed the first oc... | g62573 | [
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-0.01880866475403309,
0.03416411578655243,
-0.0029166671447455883,
0.06249428912997246,
0.02782... |
<p>I am unclear to on how to find the Fisher information of $\lambda$ in the iid sample $X_1,...,X_n$. </p>
<p>Attempt:</p>
<p>I know that the fisher information for $X$ (not in a sample) would be:</p>
<p>$I(\lambda) = - E \frac{d^2}{d \lambda^2} ln(f(x|\lambda)) = \frac{1}{\lambda^2}$</p>
<p>Where: $f_x(x|\lambda)... | g62574 | [
-0.005971367470920086,
0.01298485416918993,
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0.033313143998384476,
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0.0013518909690901637,
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-0.02948487363755703,
-0.0374935083091259,
0.061998799443244934,
0.0038902731612324715,
0.... |
<p>I have a categorical dependent variable that involves four clusters of positions. In descriptive analysis, I noticed that first cluster covered about 5% of the participants, second 6%, third 60%, and fourth 29%. I have four continuous independent variables and I am thinking of using multinomial logistic regression. ... | g62575 | [
-0.007156808394938707,
0.013158082962036133,
0.0010063396766781807,
0.011103707365691662,
0.0039728861302137375,
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0.010901426896452904,
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-0.001027689198963344,
0.0234729815274477,
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0.... |
<p>I have two questions about AICc and number of parameters.</p>
<p>I am using AICc to select the best of three models in a logistic regression - and each model has the same number of parameters. What are some compelling arguments for this method? I have G and C statistics, but these do not allow ranking. The formu... | g19718 | [
0.012383099645376205,
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0.009924790821969509,
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0.0282139852643013,
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0.02634422853589058,
0.024463584646582603,
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0.046398501843214035,
0.02562071569263935,
0.006851475685834885,
0.07891856878995895,
0.009002... |
<p>I am working with hyperspectral image data in R, so I have subset an image to a region of 5000 pixels, each containing a vector 254 bands in length.</p>
<p>I would like to cluster this data in order to try and map regions with similar surface composition.</p>
<p>Due to differences in surface reflectance, if I plot... | g62576 | [
-0.03220783546566963,
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-0.021792488172650337,
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0.011306182481348515,
0.004066417459398508,
0.010734622366726398,
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-0.0006122112390585244,
0.04226476326584816,
0.05442417412996292,
0.029644813388586044,
0... |
<p>Does glmnet provide any mechanisms to extract the regularization path from a final model? I'm using Elastic Nets (and L1) to build a binomial classifier and would like to be able to get the coefficients at each step along the path (until convergence).</p>
<p>The <code>elasticnet</code> R package has this in the <co... | g19719 | [
0.037287335842847824,
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0.003208465874195099,
0.017779534682631493,
0.07100318372249603,
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0.00565470103174448,
0.032815925776958466,
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-0.01779615320265293,
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0.0087269376963377,
0.00257189036346972,
-0.0408... |
<p>I performed enzyme kinetics experiments on a three independent preparations of an enzyme and produced the following three datasets which I separately fit to the Michaelis-Menten equation:</p>
<p>$$
V= \frac{V_{max} \times S}{K_m + S}
$$</p>
<p>I used R / nlme's nlsList function to do the fitting:</p>
<pre><code>f... | g62577 | [
-0.01225329004228115,
-0.039039842784404755,
-0.015374294482171535,
-0.004646599292755127,
-0.021605374291539192,
-0.06905478239059448,
-0.044046830385923386,
0.05359034612774849,
-0.04694013297557831,
0.05157726630568504,
-0.05423559993505478,
0.0038236624095588923,
0.06166911497712135,
0... |
<p>I would like to apply <a href="http://en.wikipedia.org/wiki/Kalman_filter" rel="nofollow">Kalman smoothing</a> to a series of data sampled at irregular time points. There is a claim on Stack Exchange that <a href="http://stats.stackexchange.com/a/34046/20486">"For irregular spaced time series it's easy to construct ... | g62578 | [
0.000439075956819579,
-0.009971302933990955,
0.01123728882521391,
-0.017508408054709435,
-0.026872284710407257,
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0.030156400054693222,
0.06294463574886322,
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-0.019606351852416992,
-0.005053672008216381,
-0.037734005600214005,
0.051030583679676056,
... |
<p>I have an set of input ranges <code>{[a1, b1], [a2, b2], ...}</code>. Each <code>a</code> and <code>b</code> represent integer values.</p>
<p>I have a constant "segment length" <code>i</code> that is always less than <code>b-a</code> for all <code>a</code> and <code>b</code>.</p>
<p>I would like to uniformly sampl... | g19720 | [
-0.012998655438423157,
0.027688903734087944,
-0.021214086562395096,
-0.06454119086265564,
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0.014342383481562138,
0.001544210477732122,
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0.016123514622449875,
-0.023172223940491676,
0.024259908124804497,
-0.024524493142962456,
... |
<p>I need to fit a bivariate data using kernel regression (local polynomial regression).
It should satisfies two conditions.</p>
<ul>
<li><p>$\frac{dy}{dx_1} \geq 0$ for all $x_2$</p></li>
<li><p>$\frac{dy}{dx_2} \geq 0$ for all $x_1$</p></li>
</ul>
<p>How can I incorporate these two conditions into local polynomial ... | g62579 | [
0.06602060049772263,
-0.00543987238779664,
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-0.060794953256845474,
0.024196814745664597,
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0.032791029661893845,
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-0.006326710339635611,
0.026872944086790085,
0.008743196725845337,
-0.011261790059506893,
0... |
<p>Could you give me some clarification about data mining and artificial intelligence algorithms? What mathematics base they used for? Could you give me starting point, in mathematics, to understand these types of algorithms? </p> | g19724 | [
0.06539420783519745,
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0.02524847909808159,
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-0.011851427145302296,
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0.0540311299264431,
0.10656660795211792,
0.01858... |
<p>I have conducted a clinical trial using two groups with two different treatment modalities. I have measured different physical and biochemical parameters (e.g pulse, systolic blood pressure, serum sodium level etc.) in each group at different time intervals (say pre-intervention, after 1 month and after two months).... | g37477 | [
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0.007004600949585438,
-0.021962929517030716,
0.012210849672555923,
0.031968794763088226,
0.018581513315439224,
-0.005401637405157089... |
<p>@whuber has demonstrated how to <a href="http://stats.stackexchange.com/questions/24257/how-to-simulate-multivariate-outcomes-in-r">simulate multivariate outcomes</a> ($y_1$, $y_2$, and $y_3$) for one time point.</p>
<p>As we know, longitudinal data often occur in medical studies. My question is how to simulate rep... | g62580 | [
-0.01861884444952011,
-0.023665277287364006,
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0.014619612134993076,
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0.015835251659154892,
-0.016246473416686058... |
<p>I have a total of 7 data sets that i want to compare. Each set has 2 samples only, for which i want to calculate standard deviation. Will my value of standard deviation be reliable? Or is it a a better option to compare them using only average value of the 2 samples.</p> | g62581 | [
0.0048947627656161785,
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0.0027413940988481045,
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-0.07082203030586243,
0.08695641160011292,
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0.03484484925866127,
... |
<p>I am working in text classification in RapidMiner where, because of the nature of my problem, I cannot use the built-in k-fold cross validation strategy, so I decided to create 10 copies of my dataset manually in order to incorporate the k-fold cross validation $(k = 10)$. However I have a few confusions regarding i... | g62582 | [
0.019230250269174576,
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0.003407476469874382,
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0.04115394502878189,
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0.05409375950694084,
0.07584026455879211,
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0.020625311881303787,
-0.003969560842961073,
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0.027309460565447807,
-... |
<p><a href="http://en.wikipedia.org/wiki/Effect_size#Effect_sizes_for_associations_among_categorical_variables" rel="nofollow">Wikipedia</a> gives some information on this. However, I seek more detailed information on when odds ratios/risk ratios are better, and why one is better than the other in certain circumstances... | g62583 | [
0.02511291205883026,
0.05984555184841156,
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0.022200288251042366,
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-0.005211466923356056,
0.04796620085835457,
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0.0399499386548996,
0.075... |
<p>I'm an ecology PhD student, but unfortunately not a very mathematically sophisticated one. I am interested in ways to compare two non-linear models. I was really impressed with <a href="http://stackoverflow.com/questions/6723157/how-to-compare-two-curves-arrays-of-points">this answer</a>, which covers part of my qu... | g38799 | [
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0.034301575273275375,
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0.112493596971035,
0.0... |
<p>Given the sample mean $\bar{x}$ and the sample variance $s^2$ of a random variable $X$, is it possible to estimate the shape $\sigma^2$ and log-scale $\mu$ of the log-normal distribution, with probability density function
$$f_X(x;\mu,\sigma^2) =\frac{1}{x \sqrt{2 \pi \sigma^2}}\, \mathrm{exp}\left( {-\frac{(\ln x - ... | g62584 | [
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0.042935602366924286,
0.035308852791786194,
... |
<p>I want to subsample two equivalent (in terms of features/columns) data sets in a way that the new subsampled data sets have the same joint probability distribution. To explain it better on an example:</p>
<p><strong>Example</strong>: Assume I have salary data for software developers and construction workers availab... | g62585 | [
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<p>I have to conduct a time series regression analysis.
Before proceeding I tested for stationarity and I verified that the variables are distributed according to the normal probability distribution.
After I regressed the time series model, I tested error autocorrelation and the presence of heteroskedasticity.
There is... | g62586 | [
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<p>Please help me, I don´t have any idea how to solve this problem. If $\textbf{A} \sim W_p(\mathbf{\Sigma}, m)$ and $\textbf{B} \sim W_p(\mathbf{\Sigma}, m)$ are independent Wishart matrices, show that $|\textbf{A}|/|\textbf{A}+\textbf{B}|$ has the $\Lambda(p,m,n)$ Wilk's lambda distribution.</p>
<p>I would be very g... | g19730 | [
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<p>First off, I apologize if it seems like I'm flooding the board, but I'm new to modelling and a lot of the questions that are coming up aren't closely related to one another, so it seems better to put them in their own threads. </p>
<p>I'm trying to predict win percentage of a particular team in a particular season ... | g38327 | [
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<p>How do <a href="http://stats.stackexchange.com/questions/14474/compendium-of-cross-validation-techniques">different cross-validation</a> methods compare in terms of model variance and bias? </p>
<p>My question is partly motivated by this answer: <a href="http://stats.stackexchange.com/questions/61546/number-of-fold... | g19731 | [
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<p>I have a series of xyz data in a unit cube. It forms a sort of tapered & curved cylinder. It will begin and end at 0,0,0 and 1,1,1. I want some sort of best fit curve down the 'axis' of this shape. And I need to take a new xyz point and map/project it onto this best fit curve. If I was expecting a straight ... | g62587 | [
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<p>I am fairly new to statistics. The concept of bootstrapping has been confusing to me.</p>
<p>I know that normality of the sampling distribution is required to use certain tests such as the t-test. In cases when the data are not normally distributed, by requesting "bootstrapping" in t-tests in SPSS would this circum... | g62588 | [
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<p>How do I test for a "location shift" in something like the mean or median if the shape of the distribution has changed quite significantly between groups?</p>
<p>Often an experimental intervention seems to completely change the distribution of the data. For example, If I measure limb length in control and toxin-exp... | g62589 | [
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<p>If I have a one-dimensional random walk with position $X(\text{t})$ with $X(0)=0$ and $\text{Var}(X(1)) = 1$,
and I observe $X(1) = \text{c}$, what are the distributions of the minimum and maximum values of x between times 0 and 1 conditional on c, and what is the distribution of the range over this time interval?<... | g62590 | [
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<p>In my survey, I grouped 67 unique counseling techniques that I thought were related to one another (based on theory and conceptual similarity) into six "counseling domains" using fairly intuitive, descriptive but brief labels (e.g., rapport-building or confrontation). In the first section of the survey, I asked resp... | g62591 | [
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<p>I need to analyse a dataset of clinical rehabilitation data. I am interested in hypothesis-driven relationships between quantified "input" (amount of therapy) and changes in health status. Although the dataset is relatively small (n~70) we have repeated data reflecting temporal changes in both. I am familiar with no... | g38806 | [
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<p>I want to learn about Radial Basis Function Neural Networks, can you please suggest a good introduction or tutorial? All the introductions I found are rather short or incomplete or so. </p> | g62592 | [
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<p>Some material I've seen on machine learning said that it's a bad idea to approach a classification problem through regression. But I think it's always possible to do a continuous regression to fit the data and truncate the continuous prediction to yield discrete classifications. So why is it a bad idea?</p> | g62593 | [
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<p>Given the regression model</p>
<p>$y=\beta_0 + 300*ln(x_1) - 15 * (ln(x_1))^2 + \beta_3*x_2 + ... + u $</p>
<p>$x$ ranges from 1 000 to 30 000 (6.9 to 10.3 on a logarithmic scale). How to interpret the diminishing effect that $x_1$ has on $y$? Is it possible to interpret it for small changes in $x_1$ analog to a "... | g62594 | [
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<p>Quoting from a Wikipedia article on <a href="http://en.wikipedia.org/wiki/Naive_Bayes_classifier#Parameter_estimation">parameter estimation for a naive Bayes classifier</a>: "a typical assumption is that the continuous values associated with each class are distributed according to a Gaussian distribution."</p>
<p>I... | g62595 | [
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<p>I need some help. I have never used the cointegration process neven before and I am not used working with econometrics.I have a model with 5 explanatory quarterly variables,52 observations and the lags selection criteria proposed 4 lags (given in the choice maximum lags: 4 lags)</p>
<p>I would like to ask about the... | g62596 | [
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<p>Suppose we are given $\mu$ and $\sigma$ for a lognormal distribution with random variable $X$. $\mu$ is the mean of the variable's logarithm and $\sigma$ is the standard deviation of the variable's logarithm. Then if $Z$ is sampled from a standard normal distribution ($Z$ has mean 0 and std deviation 1), </p>
<p>... | g62597 | [
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<p>What is best statistical model to assess effect of <code>habitat type</code> and <code>year</code> (categorical factors), and <code>plant species percent coverage</code> (%), as independent variables on the dependent variable: <code>insect abundance</code> (count)? </p>
<p>I have zeros in my data and the DV is not... | g49647 | [
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<p>Given $Z_1, ..., Z_n, \sim\mathcal{N}(0, θ^2), θ>0$. Define $X_i=|Z_i|$ and consider estimation of $\theta$ and $θ^2$ on the basis of the random sample $X_1,...X_n$. Find the uniformly minimum variance unbiased estimator (UMVUE) of $θ^2$.</p> | g62598 | [
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<p>Say I have some data on people where I have a measure of their general health (some score out of 1000), the number of apples they eat in a year, and the number of oranges they eat in a year. </p>
<p>Then I do a multiple regression and I get something like:</p>
<p>$\hat Y = 442.22 + 1.1a + 0.7o$</p>
<p>where $a$ i... | g62599 | [
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<p>I've obtained a logistic regression model (via <code>train</code>) for a binary response, and I've obtained the logistic confusion matrix via <code>confusionMatrix</code> in <code>caret</code>. It gives me the logistic model confusion matrix, though I'm not sure what threshold is being used to obtain it. How do I ob... | g62600 | [
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<p>I really hope someone can help me as i have been reading about this stuff and i am still really confused!</p>
<p>I have a dataset of 180 chemical compounds with 2 data (numerical) values each - i want to see if there is a difference between these two data points for each of the compounds for the whole dataset howev... | g62601 | [
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<p>Good day! Our group conducted a classroom research about Social Goals Role on Student Mindset. For this study, we asked 42 college students to answer 2 sets of questionnaire. The first survey consists of 17 items (YES/NO) while the second set consists of 3 items with 6-point Likert scale.</p>
<p>Please help me on w... | g62602 | [
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<p>I am doing multinomial logistic regression.</p>
<p>Dependent variable is categorical with 6 categories. 6 Independent variables are measured on an interval scale (included as covariates in SPSS)</p>
<p>Now I am watching the LR test. None of the independent variables have a $\chi^2$ value and no degrees of freedom ... | g49648 | [
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<p>As per answers to <a href="http://machinelearning.stackexchange.com/questions/84/how-to-decide-on-the-correct-number-of-clusters">this question</a>, there are shortcomings in the heuristics of deciding on the number of clusters.</p>
<p>A more robust approach could be <em>probability based clustering</em>: from a pr... | g62603 | [
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<p>The most well-known bandit algorithm is upper confidence bound (UCB) which popularized this class of algorithms. Since then I presume there are now better algorithms. What is the current best algorithm (in terms of either empirical performance or theoretical bounds)? Is this algorithm optimal in some sense?</p> | g19743 | [
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<p>Am I understanding correctly that growth mixture model is just Gaussian mixtures applied to coefficients of polynomials fitted to the time-series data?</p>
<p>For example, we have 1000 cases, with 3 measurements each. We fit, say, a quadratic equation to each which gives us 3 extra values per case (quadratic, line... | g62604 | [
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<p>I recently came across this work: </p>
<p><a href="http://cvlab.epfl.ch/alumni/oezuysal/ferns.html" rel="nofollow">http://cvlab.epfl.ch/alumni/oezuysal/ferns.html</a></p>
<p>which is a balance between the full naive Bayes assumption (full independence between the features) and absolutely no independence assumption... | g19745 | [
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<p>If you have two data sources which report their decision at different data rates, and have different "trustworthiness" how can I combine them so that I can take advantage of both of them?</p>
<p>I'm still relatively new to the statistics realm, but I am assuming that using data from multiple sources yields a better... | g62605 | [
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<p>There seem to be many machine learning algorithms that rely on kernel functions. SVMs and NNs to name but two. So what is the definition of a kernel function and what are the requirements for it to be valid?</p> | g19747 | [
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<p>Example: I want to compare the number of successes in a sample of ~10,000,000 independent bernoulli trials against a known population probability of success of ~.01. Thus, expected success count for 10,000,000 trials should be 100,000. </p>
<p>What's the quickest hypothesis test to implement for a large n, small p?... | g62606 | [
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<p>See also <a href="http://stats.stackexchange.com/questions/13597/on-the-strength-of-weak-learners">a similar question on stats.SE</a>. </p>
<p>In <a href="http://en.wikipedia.org/wiki/Boosting">boosting</a> algorithms such as <a href="http://en.wikipedia.org/wiki/AdaBoost">AdaBoost</a> and <a href="http://en.wikipe... | g38816 | [
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<p>In the past few years, various scholars have raised a detrimental problem of scientific hypothesis testing, dubbed "researcher degree of freedom," meaning that scientists have numerous choices to make during their analysis that bias towards finding with p-value < 5%. These ambiguous choices are, for example, whic... | g3890 | [
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<p>I have just started playing around and reading about Bayes Nets. Here is a snippet of code using the bnlearn package in R, which seems to be a fantastic tool.</p>
<pre><code>install.packages("bnlearn")
library(bnlearn)
data <- data.frame(matrix(c("sunny","hot","high","weak","no",
"sunny","hot",... | g19752 | [
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<p>I am trying to do a grid search for a polynomial kernel. I have used the normal grid search on polynomial kernels which is wrong. I only varied $c$ and $\gamma$... but I need to vary $a$ and $b$... Is there any fast method to do grid search for polynomial kernels? </p>
<p>Polynomial kernel: $K(x_i, x_j) = (\gamma x... | g19753 | [
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<p>Assume a set of nodes is scattered over a 2D surface $\mathcal{S}$ so that for any given $\mathcal{A} \subset \mathcal{S}$, the number of nodes inside $\mathcal{A}$ follows a Poisson distribution with parameter $|\mathcal{A}| \rho$, where $|\mathcal{A}|$ shows the area of the subset $\mathcal{A}$ and $\rho$ is the i... | g62607 | [
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<p>I would like to use the following type of model and am wondering if someone could let me know if this technique has been studied before (I assume it has) and where to learn more about it?</p>
<p>The idea is simple. I have a Markov process with a possibly infinite state space S. I have a partition P of S into a fini... | g62608 | [
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<p>It's been a while since I looked at partitioning trees. Last time I did this sort of thing, I like party in R (created by Hothorn). The idea of conditional inference via sampling makes sense to me. But rpart also had appeal. </p>
<p>In the current application (I can't give details, but it involves trying to determi... | g62609 | [
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<p>How do you interpret an odds ratio of an interaction between two continuous variables $x_1, x_2$? Would you fix $x_2$ and let $x_1 = x$ and $x_1 = x+1$?</p> | g49894 | [
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