question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I am encountering some problems with setting up a multinomial logistics regression (stepwise).</p>
<p>My data/model is the following:</p>
<ul>
<li>Dependent variable: strategy1/strategy2/no preference</li>
<li>"Indenpendent" variable: risk perception value (prob*impact in
percentage)</li>
<li>Moderator: risk profi... | g63546 | [
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<p>I currently have a experiment with a within subject design, where I repeatedly measure reaction times (RT). Reaction times for each category of reaction were measures multiple times. However now the problem is, that the mean of all reaction times for each subject may differ by quite a lot, as some person may react m... | g21260 | [
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<p>I was reading this paper <a href="http://cs.ru.nl/~perry/publications/2011/ICANN2011/groot-icann2011.pdf" rel="nofollow">http://cs.ru.nl/~perry/publications/2011/ICANN2011/groot-icann2011.pdf</a> and I am a bit confused how this was derived</p>
<p>$p(f|Y) \propto p(f)*p(Y|f) \propto exp^{(-\frac{1}{2}f^TK^{-1}f-\... | g40590 | [
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<p>I am confused. Given</p>
<p><img src="http://i.stack.imgur.com/WAUg6.png" alt="enter image description here"></p>
<p>how come this is derived?<a href="http://i.stack.imgur.com/JQsVu.png" rel="nofollow">enter image description here</a></p>
<p><img src="http://i.stack.imgur.com/JQsVu.png" alt="enter image descripti... | g21261 | [
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<p>If I have a QQ plot with two extreme outliers (picture below) how should I interpret it? Do I drop the outliers? Can I treat it as normal?<img src="http://i.stack.imgur.com/N3ONG.png" alt="enter image description here"></p> | g10382 | [
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<p>I have a time series of daily measurement data, if you plot the histogram of the data points of the time series, you see long tail and high positive scewness. Also zero values is an important state. </p>
<p>My goal is to use Markov Chain to model the time series, but the measurement data are integers without upper ... | g63547 | [
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<p>I am having trouble getting a fractional polynomial logistic model to converge using Stata 12. </p>
<pre><code>fracpoly, logistic: y x
</code></pre>
<p>I have tried</p>
<ul>
<li>centering the dependent variable</li>
<li>transforming the variable </li>
<li>adding a fixed value to every observation so that there ar... | g63548 | [
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<p>You have received a radioactive mass that is claimed to have a mean decay rate of at least 1 particle per second. If the mean decay rate is less than 1 per second, you may return the product for a refund. Let X be the number of decay events counted in 10 seconds.</p>
<p>Part a. If the mean decay rate is exactly 1 p... | g63549 | [
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<p>Beer's law from chemistry says that the absorbance of a liquid $A$ is proportional to the concentration $C$, so:
$$A = kC$$
The standard thing to do then is to prepare a set of solutions with known concentrations, measure the absorbance to form a 'standard curve' (a calibration curve basically), and do a simple line... | g63550 | [
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<p>In searching for any info about <strong>marginal model</strong> and <strong>random-effects model</strong>, and how to choose between them, I have found some info but it was more-or-less mathematical abstract explanation (like for example here: <a href="http://stats.stackexchange.com/a/68753/38080">http://stats.stack... | g63551 | [
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<h3>Initial Question:</h3>
<p>I am trying to calculate inter-rater reliability. Previous researchers in this area have used intraclass correlation. SPSS has options for two-way random, mixed random and one-way random models. SPSS help says choose the right one based on whether the 'people effects are random' and 'item... | g63552 | [
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<p>I have a mixed model with three random effects and many fixed effects. I set aside some of my data to validate my final model and now I would like to compute the $R^2$ on the validation set, in <code>R</code>. </p>
<p>I found some code for a mixed model with one random effect but not for a model with more than on... | g37629 | [
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<p>So I've been compiling a list of fictional (anime/manga) characters which meet a certain criteria (<a href="http://www.gwern.net/hafu#list" rel="nofollow">http://www.gwern.net/hafu#list</a>) from a universe of all anime/manga characters since 1963 (which is of unknown total size - but very large!), and I've been won... | g557 | [
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<p>Does anyone know of a step-by-step guide for the practical implementation of Gifi Methods for Optimal Scaling in R: The Package homals? Although I have an OK theoretical understanding (thanks chl for directing me to articles), I'm a tech novice and some of the language/technical information is a bit too complicated ... | g40606 | [
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<p>I am trying work out the variance of the population estimate var (R) where R = X/Y (X = sum(x) and Y = sum(y)). For each member of the population I know y and I have stratified the population and taken a random sample of each strata. For each member of the sample I need to estimate x. x is not known with certaint... | g21270 | [
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<p>I ran a simulation on that for mcnemar test, and the answer seemed to be yes.</p>
<p>I was wondering if this can always be said to be the case that the exact P value is higher (or not smaller) then the p value which is arrived to through an approximation.</p>
<p>some code for example:</p>
<pre><code>set.seed(234)... | g63553 | [
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<p>In recent research I pursue a MANOVA model on a dataset comprised of 50 measured characters and several grouping factors that I need to test. When I use something like this</p>
<pre><code>summary(manova(malesM ~ popMales*manageMales*biomeMales), test = "Wilks")
</code></pre>
<p>I get 2.2e-16 significance for eve... | g21276 | [
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<p>Looking at the following dataset:</p>
<pre><code> Date Visits Carts carts Orders
Created converted Created
2011-11-11 12277 161 9 36
2011-11-12 11871 93 5 19
2011-11-13 13072 107 8 8
2011-... | g40613 | [
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<p>Reading a paper, I realized that a polynomial regression equation was published with its associated standard error and sample size. That regression relates enamel thickness ($y$) and enamel formation time ($x$). I only know the regression equation, not the raw data.
This is the regression equation:</p>
<p>$$y=8.7+0... | g34116 | [
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<p>I'm clustering a set of data but I don't have truth document that allow me to evaluate the result of clustering (I have unlabelled data), so I can not use an external evaluation measure. In this case, is there any efficient evaluation measures, that will allow me to incrementally evaluate the clustering result each ... | g63554 | [
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<p>I have over 1000 respondents each with their own regression coefficients. I am analyzing data by different segments by averaging the constant and coefficient scores for each group. Sometimes I will have 2 groups (gender, yes/no questions, etc.) and sometimes I will have multiple groups (Ethnicity, age groups, etc.)... | g10392 | [
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<p>I am reading the Expectation Propagation chapter in Chris Bishop's book and there is a bit on approximating factor graphs. So, the original factor graph and the approximating factor graph looks as follows:</p>
<p><img src="http://i.stack.imgur.com/wkAVG.png" alt="enter image description here"></p>
<p>So, the origi... | g63555 | [
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<p>I have a data set (patients (15000) nested in hospitals (50)), with a number of covariates. I built a proportional hazards model in Stata, and entered site as a frailty term. I would like to report how survival varies between hospitals. I can extract the frailties and report these, but this has no straightforward, f... | g63556 | [
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<p>So I have a categorical variable with ~ 8000 types (or levels, or cardinality). The dataset is rather large (a couple million records). Most machine learning techniques are failing do to memory limits on my computer, so I think an approach may be to run a loop and do individual regressions for each category step by ... | g21283 | [
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<p><strong>Question 1:</strong></p>
<p>Suppose that data is modelled by a mixture of K probability distributions which are actually Gaussians. $P(x_i|\theta_j)$ is the probability density of the j'th cluster, for which the parameters that we want to learn are $\theta_j = \{\mu_j, \sigma_j\}$. The probability that data... | g40640 | [
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<p>In text classification and clustering, the number of features are normally big, e.g. I currently get are around 5,000 features which is already really small compared to many other text mining tasks. Given I am totally new to visualization, I have no clue about how should I plot the results from text classification a... | g63557 | [
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<p>I am transforming an unscaled density function to log scale to avoid underflow issues. </p>
<p>BI was performing integration on this function on a grid of values before I used the log transormation, to build a grid based cumulative distribution function. Then, using a draw from uniform[0,1], I was choosing the the ... | g63558 | [
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<p>I'm thinking how to tackle such a problem.</p>
<p>Let's say we have a set of products, each have some numeric characteristics <code>(x1, x2, x3)</code>. A customer is given a choice of <code>n</code> such products and buys one. Only a few of products are shown and the choice is made only between them based solely o... | g40644 | [
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<p>Consider the problem of randomly generating a $p \times p$ covariance matrix $\Sigma$ with the diagonal entries constrained to be 1, and the off-diagonal entries $\Sigma_{ij}=\Sigma_{ji} \sim Unif[-a,a]$. What is the maximum value of $a$, as a function of $p$, such that $\Sigma$ is positive definite with probabilit... | g63559 | [
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<p>(cross-posted from the R-sig ME list - maybe this is too basic for it)</p>
<p>Hello
I would like to fit piecewise linear growth curves to a number of
subjects (each with a number of observations at different abscissa),
where all the slopes for a common interval (e.g, 2 <= x < 3)
presumable arise from the same... | g21287 | [
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<p>I am comparing the error between wind turbine production and predictions from 24 hours ahead. The graphs below are using the normal distribution.</p>
<p>But can I do better?
<img src="http://i.stack.imgur.com/oNqHC.jpg" alt="enter image description here">
<img src="http://i.stack.imgur.com/tvsoC.jpg" alt="enter ima... | g63560 | [
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0.05603651702404022,
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0.... |
<p>We are running a sweepstake for the football world cup and the first three people to choose "drew" the past three winners while in a closed room.</p>
<p>Just for fun, I'd like to show the probability of this happening by chance?</p>
<p>As an extension, what is the probability that each of these 3 got the country t... | g63561 | [
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<p>So I'm trying to build my own Wald test and likelihood ratio test code within a machine learning pipeline. I can get the final fitted logistic regression coefficients from liblinear. I'm coding in MATLAB.</p>
<p>How would I get the variance of the regression coefficients and also the confidence intervals of the reg... | g8136 | [
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<p>I have two variables A={some values} and B={some values). Each value in A is not related to the corresponding value in B. How I can find the correlation between these two variables? or how can I know if these two variables have any kind of association "relationship" between them?
Just an example to make the questio... | g63562 | [
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<p>For two class labels +1 and -1, is there a case in conventional soft-margin SVM where one class does not have a margin support vector and just margin error support vectors or correct points? </p> | g63563 | [
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<p>I have a calculated standard deviation, mean and number of elements in list. For every new numerical entry to list, I should compute new standard deviation via using old one and new entry data. I have stucked how to do in paper so my code implementation is also. How can I formulate new standard deviation after new e... | g49676 | [
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<p>I am writing my thesis on VaR and ES risk measurements and have encountered some issues with how to best test the accuracy of ES statistics.</p>
<p>My understanding of the topic is that backtesting ES adequately is extremely difficult or even impossible, as it is not an elicitable risk measure. And I also assume th... | g21293 | [
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<p>I have an uncorrelated bivariate normal process: $X \sim N(0, \sigma_1), Y \sim N(0, \sigma_2), \rho = 0$, and I'm interested in the distribution of $Z = \sqrt{X^2 + Y^2}$.</p>
<p>I know that if I'm willing to normalize <em>X</em> and <em>Y</em> by their variance then <em>Z</em> has the chi distribution with 2 degr... | g63564 | [
0.0203288272023201,
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<p>It is a general and maybe stupid question, but it will help me to avoid a mistake. To test the dependence of continuous variable on nominal with parametric test (t-test, ANOVA), "the data has to be normally distributed" (distribution have to be not much violated from normal). </p>
<p>But I don't clearly understand:... | g21297 | [
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<p>I was wondering if anybody knows of the existence of an R package which implements entropy-based methods (maximum empirical likelihood, maximum exponential empirical likelihood, minimum discrepancy estimators, etc.)? Thanks</p> | g63565 | [
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<p>I was wondering whether the Nelson-Aalen estimator can be applied to discrete-time multi-state data (in months). I ask this because it seems that literature tends to present it only in the continuous-time framework (in particular within the so called "counting processes" approach).</p>
<p>Since in discrete time dat... | g44746 | [
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<p>Consider for instance the balanced one-way random effects ANOVA model:
$$(y_{ij} \mid \mu_i) \sim_{\text{iid}} {\cal N}(\mu_i, \sigma^2_w), \quad j=1,\ldots,J,
\qquad
\mu_i \sim {\cal N}(\mu, \sigma^2_b), \quad i=1,\ldots,I. $$</p>
<p>In <a href="http://stats.stackexchange.com/questions/41177/prediction-interval-... | g63566 | [
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0.0523... |
<p>As a follow-up to <a href="http://stats.stackexchange.com/questions/43554/model-suggestion-for-a-cox-regression-with-time-dependent-covariates-here">Model suggestion for a Cox regression with time dependent covariates</a> is the Kaplan Meier plot accounting for the time dependent nature of pregnancies. In other word... | g37710 | [
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<p>What's the difference between an <strong>unrestricted</strong> and a <strong>restricted</strong> VECM? </p>
<p>I believe a hint lies within the <code>cajorls()</code>[<a href="http://www.inside-r.org/packages/cran/urca/docs/cajorls" rel="nofollow">1</a>] function of R language's <code>urca</code>[<a href="http://cr... | g41783 | [
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<p>I have run a repeated measures MANOVA for my dissertation study in clinical psychology but am struggling a little bit with the proper write up. I have found several examples on the internet and through my school library for written results, but none specifically for a RM MANOVA with one IV and only two DV's (for pre... | g40315 | [
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<p>I have come across some formula for calculating the confidence interval (CI) of data from an Inverse Gaussian distribution. But, being really new in stats, I am unable to figure out what to do.</p>
<p>On page 51 of <a href="http://www.idescat.cat/sort/sort321/32.1.2.arefi-etal.pdf" rel="nofollow">this</a> document,... | g63567 | [
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<p>the two likert scales will determine disease perception A.severity B. susceptibility.
The alogorithm will determine stage the of intention to be screened for disease which the participants can fall into 1 of 6 stages. I am not sure of the best way to conduct my analysis I was leading toward ordinal regressional ana... | g63568 | [
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<p>I want to randomly generate 1000 normal variates (using <code>rnorm</code>, <em>e.g.</em>) that have mean 100. 25% of the 1000 numbers should be over 110.</p>
<p>How can I do this in <code>R</code>? </p>
<p>I only got this far: </p>
<pre><code>x <- rnorm(1000,100,1)
</code></pre> | g63569 | [
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... |
<p>I have a small population and it is possible to estimate Population regression function from the data. The size of the population is very small. It is only eight. I think since the regression relates to poulation, there is no need to conduct any testing. Am I correct?</p> | g63570 | [
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<p>I have obtained some data about how complexity of Java open source projects varies with time. I want to fit a curve to the data, however I am unable to figure out the right kind of transformation. I tried some that came immediately to my head: $\ 1/y \sim x,\ \log(y) \sim x,\ y \sim 1 + x + x^2$, etc. but I never go... | g63571 | [
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<p>Suppose that there are two two-dimensional maps. For simplification, let's say one map is the temperatures in the 48 continental U. S. states, and the other map is the corresponding humidities. The data of temperature and humidity are collected at one specific moment at some equally-spaced (e.g., 1000) locations. If... | g21310 | [
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<p>I have a logistic regression model which implicitly estimates the probability that a business will default in each of 8 future quarters conditional upon survival to that quarter. In other words, I have 8 sets of coefficients to give me 8 different conditional probabilities based on the covariates at t=0. (cumulative... | g63572 | [
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<p>I am curious to learn whether there are any best practises in creating random variables for a Monte Carlo simulation using input such as skewness and kurtosis information of a particular distribution. Of course those need to be used in addition to the average and standard deviation. </p>
<p>My objective is to creat... | g278 | [
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<p>If I have a variable with 4 levels, in theory I need to use 3 dummy variables. In practice, how is this actually carried out? Do I use 0-3, do I use 1-3 and leave the 4's blank? Any suggestions?</p>
<p>NOTE: I'm going to be working in R.</p>
<p>UPDATE: What would happen if I just use one column that uses 1-4 c... | g40668 | [
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<p>We define a state i to be recurrent if $\sum\limits_{n=0}^\infty P(X_n=i,X_k \neq i$ for $1\leq k < n | X_0=i)$=1.</p>
<p>Why do we take infinite series over the probability? Why don't we define recurrent just as:</p>
<p>$P(X_n=i,X_k \neq i$ for $1\leq k < n | X_0=i)$=1</p>
<p>Doesn't this already mean, tha... | g34705 | [
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<p>A signal detection experiment typically presents the observer (or diagnostic system) with either a signal or a non-signal, and the observer is asked to report whether they think the presented item is a signal or non-signal. Such experiments yield data that fill a 2x2 matrix:
<img src="http://i.stack.imgur.com/JktFQ.... | g21315 | [
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<p>In boosting, each additional tree is fitted to the unexplained variation in the response that is currently un-modelled. If we are using squared-error loss, this amounts to fitting on the residuals from the aggregation of the trees fitted up to this point. I am not clear on whether it is at this point that the shrink... | g63573 | [
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<p>In 1999, Beyer et al. asked,
<a href="http://www.cis.temple.edu/~vasilis/Courses/CIS750/Papers/beyer99when_17.pdf">When is "Nearest Neighbor" meaningful?</a></p>
<p>Are there better ways of analyzing and visualizing
the effect of distance flatness on NN search since 1999?</p>
<blockquote>
<p>Does [a given] data ... | g40679 | [
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<p>In response to a growing body of statisticians and researchers that criticize the utility of null-hypothesis testing (NHT) for science as a cumulative endeavour, the American Psychological Association Task Force on Statistical Inference avoided an outright ban on NHT, but instead suggested that researchers report ef... | g40683 | [
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<p>How can I generate random numbers that follow a student-<em>t</em> distribution?
From several sources I understand that this can be done using a random sample of size $n$ drawn from a normally distributed population, as follows:</p>
<p>$$
t = \frac {(x - m)} {(s/\sqrt n)}
$$</p>
<p>Where $x$ is the sample mean, $m... | g63574 | [
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<p>I'm reading through a thesis at the moment which uses a "well known result from information theory", namely</p>
<p>$\mathrm{argmax}_\mathbf{g}\,\mathbf{f}\,\mathrm{log}\,\mathbf{g} = \mathbf{f}$,</p>
<p>for two probability vectors $\mathbf{f}$ and $\mathbf{g}$. I'm having trouble actually finding the source or a n... | g21316 | [
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-0.0... |
<p>I would like to know how to calculate the degree to which multiple IVs share variances with each other in predicting for the DV. For example, A, B, C, D and E predicts for Z. How do I calcuate the degree of shared variance for A, B, C, D and E in predicting for Z? Thank you!</p> | g63575 | [
0.011464552953839302,
0.01106423418968916,
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0.012236949987709522,
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0.02297055535018444,
0.027339650318026543,
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-0.028298035264015198,
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0.030132723972201347,
0.013622813858091831,
0.... |
<p>I am working with a set of historical data that I did not collect myself. I cannot add to this data set in any way. For a 350-year period I have many thousands of data points, each associated with one of ~50 time points. Some of the time points have hundreds of data points associated with them, so I'm sure that thos... | g63576 | [
0.027521073818206787,
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0.0007307499181479216,
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0.025012603029608727,
-0.00302008748985826... |
<p>On page 110 of <em>McFadden,1973 - Conditional logit analysis of Qualitative Choice Behavior, Frontiers in Economics, ed Zarembka, New York: Academic Press, pp. 105-142</em> the following three Axioms are made:</p>
<blockquote>
<p><strong>Axiom 1: Independence of Irrelevant Alternatives (IIA):</strong> </p>
... | g63577 | [
-0.005566826555877924,
0.046584390103816986,
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0.0008374520693905652,
0.02450970932841301,
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0.04884500801563263,
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0.019421972334384918,
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0.10372155159711838,
0.018435344099998474,
0.02447... |
<p>Can you suggest me any random effect linear model in R? At the moment I am using <strong>lmer</strong>, but I would like to know if there is any other similar function.</p>
<p>Thank you</p> | g63578 | [
-0.023689690977334976,
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0.01528703048825264,
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0.001059858943335712,
0.006402167957276106,
-0.004779462236911058,
0.02783822827041149,
0.03768400847911835,
-0.003078500973060727,
0... |
<p>I have a distribution of frequencies (1000 data points) expressed as %. The list of data looks like this: </p>
<blockquote>
<p>3.10%<br>
1.80%<br>
1.70%<br>
1.70%<br>
1.60%<br>
1.60%<br>
1.50% </p>
</blockquote>
<p>I would like to check for normality distribution of such data usin... | g21320 | [
0.031205497682094574,
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0.0060638063587248325,
-0.028993899002671242,
0.006519770715385675,
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0.014369303360581398,
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0.007973147556185722,
0.020258966833353043,
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0.04415364935994148,
0.014151792973279953,
0.... |
<p>I want to fit a Gaussian Process with about 50,000 training examples and 130 features using <a href="http://scikit-learn.org/0.13/modules/gaussian_process.html" rel="nofollow">Scikit-learn</a>. Right now, I only have 1 theta hyperparameters as I run the process with all defaults. But I get a MemoryError when it trie... | g63579 | [
0.02552068792283535,
0.001056913984939456,
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0.047523777931928635,
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0.02773023582994938,
0.0327250100672245,
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0.001588617218658328,
0.02086310088634491,
0.01823643036186695,
0.058880... |
<p>For a publication I'm looking for references for generic requirements of evaluation/fitness functions in evolutionary (more specifically genetic) algorithms.</p>
<p>I could come up with some requirements myself (efficient implementation, intuitive results, etc.) but I would like some references to existing work, si... | g63580 | [
-0.01953132264316082,
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0.015404969453811646,
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0.053320564329624176,
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0.043694060295820236,
0... |
<p>I've recently extended my genetic algorithm in such a way that it constructs a Pareto front, instead of weighing the different quality dimensions.
The quality dimensions are not related to 'spacial' information, so no natural x,y,z candidates. They are real quality dimensions (for instance recall, precision, cost, e... | g63581 | [
-0.010143288411200047,
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0.005175922531634569,
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0.03855995833873749,
0.008358906954526901,
0.08920110762119293,
0.0109... |
<p>I'm looking for a clustering implementation with the following features:</p>
<ul>
<li>Support for high-dimensional data. Now I have approximately 160.000 dimensions/features.</li>
<li>Be able to manage sparse matrix. That is, not only to read sparse matrices, but also capable of making operations in this format.</l... | g63582 | [
0.01672663353383541,
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0.004414981696754694,
0.008957887999713421,
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-0.04265586659312248,
0.029113084077835083,
0.03773944824934006,
0.08984468877315521,
-0.03... |
<p>I would like to generate a random correlation matrix such that the distribution of the entries (except 1) look approximately like normal.</p>
<p>The motivation is this. For a set of n time series data, the correlation distribution often look quite close to normal. I would like to generate many "normal" correlation ... | g63583 | [
-0.008555657230317593,
0.03669249266386032,
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0.049312181770801544,
0.022649206221103668,
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0.04501168429851532,
0.005335038993507624,
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0... |
<p>I ran a GEE model, with a dependent variable of "percent of total students with an unexcused absence," using a binomial family. My dependent variable is basically a proportion, with range from 0 to 1 to obey the rules of the binomial family.</p>
<p>I understand that the difference between the non-event/event 0-1 is... | g21325 | [
-0.05719882249832153,
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0.02155018039047718,
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0.0253603532910347,
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0.03979438543319702,
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0.06502988934516907,
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<p>As part of my dissertation I am looking into the relationship between temperature and methane emissions. A large proportion of this work relies on statistical interpretation and analysis. When plotting the link between flux and temperature SPSS outputted a 'quadratic' line of best fit with very little variation from... | g63584 | [
0.0515362024307251,
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0.04538547247648239,
-0.017021149396896362,
0.06709454953670502,
0.0144... |
<p>I am trying to fit a general linear model in which each regressor consists of 1s and 0s only.</p>
<p>Suppose my design matrix is as follows:</p>
<pre><code>1 0 0 0 0 0 0 0 0
0 1 0 0 0 0 0 0 0
0 0 1 0 0 0 0 0 0
0 0 0 0 0 0 1 0 0
0 0 0 0 0 0 0 1 0
0 0 0 0 0 0 0 0 1
0 0 0 1 0 0 0 0 0
0 0 0 0 1 0 0 0 0
0 0 0 0 0 1 0 ... | g63585 | [
0.006159450393170118,
0.004649825394153595,
-0.005017466843128204,
-0.033068928867578506,
0.10688494145870209,
0.006089523434638977,
0.013773643411695957,
0.02430439554154873,
-0.038864344358444214,
-0.049172867089509964,
-0.041916921734809875,
0.0013217807281762362,
0.0037445060443133116,
... |
<p>Suppose you divide users into two groups by flipping a coin for each user. Now you measure the number of actions in each group (say, number of total clicks). How do you test if the two groups are different?</p>
<p>For the number of users in each group, I would use a chi-squared test between expected # users (tota... | g21332 | [
-0.027162516489624977,
0.06363426893949509,
0.0026289031375199556,
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0.05164244771003723,
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0.08556587994098663,
0.0319070965051651,
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0.008170519024133682,
0.010130426846444607,
0.027283020317554474,
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-0.... |
<p>I am studying <em><a href="http://rads.stackoverflow.com/amzn/click/0262013193" rel="nofollow">Probabilistic Graphical Models</a></em>, a book for self-study. Do edges in a <a href="https://en.wikipedia.org/wiki/Directed_acyclic_graph" rel="nofollow">directed acyclic graph (DAG)</a> represent causal relations? </p>
... | g63586 | [
-0.02388458326458931,
0.008204052224755287,
-0.02174501121044159,
-0.05311863496899605,
0.037683695554733276,
-0.033578239381313324,
0.07962039858102798,
0.013461488299071789,
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-0.09355444461107254,
0.05864987522363663,
0.009564494714140892,
0.11032270640134811,
0.00425... |
<p>I wrote a Python script searching text for words and separating unique and non unique words. Running the pages I have through my program, I find 1041 unique words out of 3742 total, so roughly 27% of all the words are unique. Yet when I look at the first word of each page, 33 of the 44 words starting each page are... | g63587 | [
-0.011313863098621368,
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0.007417635526508093,
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0.02274925820529461,
0.0752514973282814,
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-0.00797642208635807,
0.013825831934809685,
-0.00818698387593031,
-0.030990397557616234,
0.0... |
<p>I used R optim() to find min log likelihood, however the diagonal elements of the inverse of Hessian matrix turns to be negative..</p>
<pre><code>> round(diag(solve(KFopt$hessian)),2)
[1] 0.00 -0.08 -0.03 0.00 -0.47 -0.18 -167.32
</code></pre>
<p>Does that mean the optimization is wrong? So what s... | g63588 | [
0.014194672927260399,
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0.0006766578298993409,
0.014271889813244343,
0.004135473631322384,
0.00618471996858716,
0.022358685731887817,
0.004631900694221258,
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-0.02453724667429924,
-0.014561101794242859,
0.03350008279085159,
0.01018700934946537,
0.01... |
<p>Title says enough... so far, I've been using Shapiro-Wilk's statistic in order to test normality assumptions in small samples. Could you, please, recommend another technique?</p> | g63589 | [
0.06800920516252518,
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0.009375255554914474,
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0.05857264995574951,
0.011489475145936012,
0.019263938069343567,
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0.028572633862495422,
0.034118685871362686,
0.012444913387298584,
0.013... |
<p>Imagine that:</p>
<ul>
<li>You have a sample of 1000 teams each with 10 members.</li>
<li>You measured team functioning by asking each team member how well they think their team is functioning using a reliable multi-item numeric scale.</li>
<li>You want to describe the extent to which the measure of team effectiven... | g21336 | [
-0.03437944874167442,
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0.0002973858208861202,
-0.06961847841739655,
0.024991635233163834,
0.010364728048443794,
-0.03676226735115051,
0.00896364264190197,
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0.0036777425557374954,
0.058636412024497986,
-0.025059599429368973,
-0.015402249991893768,
... |
<p>Say I observe two groups of 10 people, measuring some quantity 100 times in each person. There will presumably be some variability across these 100 measures in each person. Can I use mixed effects analysis to assess whether this within-person variability is, on average, different between the two groups? For example,... | g40716 | [
-0.03878049924969673,
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-0.0063444166444242,
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0.015122541226446629,
0.062045931816101074,
0.014805245213210583,
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-0.015990298241376877,
0.039801981300115585,
0.00366284791380167,
0.011668025515973568,
0.031... |
<p>I would like to know whether preprocessing of the dataset is required for dynamic Bayesian network inference or not?</p> | g21338 | [
-0.00507888849824667,
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0.001980316126719117,
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<p>Consider a random variable $Y$ with mean: $y = \alpha + \beta x$ and variance $\sigma^{2}$. Assume $n$ independent values of $Y$ are observed and are split into two samples such that the samples can be labelled: $n_{1}$ and $n_{2}$ ($n_{2} = n-n_{1}$); furthermore, assume that the observations in both groups share a... | g21340 | [
-0.03668941557407379,
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0.08509016782045364,
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-0.0016059166518971324,
-0.040877439081668854,
0.05310451239347458,
0.020874489098787308,
... |
<p>I have a dataset with approx. 13,000 cases in total, and approx. 1,000 cases have the outcome I am interested in predicting (sentenced to imprisonment). I have run a logstic regression on the whole sample and the model is terrible at predicting 'imprisonment' although quite good at predicting 'no imprisonment'. I tr... | g49437 | [
0.014867102727293968,
-0.009758791886270046,
0.012562361545860767,
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0.04542595520615578,
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0.03992509841918945,
0.059104081243276596,
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-0.013033452443778515,
-0.0036413664929568768,
-0.010050993412733078,
0.05870312824845314,
... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/7/locating-freely-available-data-samples">Locating freely available data samples</a><br>
<a href="http://stats.stackexchange.com/questions/11142/sites-for-predictive-modeling-competitions">Sites for predicti... | g49411 | [
-0.011670122854411602,
0.009407463483512402,
0.008580791763961315,
-0.02461438998579979,
0.02717079035937786,
-0.05737342685461044,
0.024132562801241875,
0.05069991573691368,
0.023171333596110344,
-0.05416755750775337,
0.01672782376408577,
0.0061933607794344425,
0.09474194794893265,
0.0090... |
<p>I am wondering if there are some better machine learning methods for medical imaging segmentation?</p>
<p>Currently, I have some relatively low-resolution MRI images and I tried to use histogram and k-means algorithm, which is an old method to do a general clustering based segmentation. However, pixel may help esti... | g21341 | [
0.030295327305793762,
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0.013497715815901756,
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0.0018074384424835443,
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0.022999005392193794,
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0.029070841148495674,
0.09211695939302444,
0.034227706491947174,
0.07368689030408859,
0.0... |
<p>Question: </p>
<blockquote>
<p>Suppose we have an ordinary household scale such as might be used in a kitchen. When an object is placed on the scale, the reading is a combination of the true weight plus a random error. You have two coins of unknown values B1 and B2. To estimate the weights of the coins, you take ... | g63590 | [
0.02541176974773407,
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0.046561431139707565,
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0.004681350663304329,
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0.0165922362357378,
-0.028577633202075958,
0.052401941269636154,
0.02686959318816662,
0.005... |
<p>I was trying myself in kaggle CIFAR competition, I trained lots of classifiers but get the same result/fail (don't know how to treat them), maybe someone could help me figure what i'm doing wrong. </p>
<ol>
<li>So in the beginning I converted images to vector (included all colours) and tried to train classifier on ... | g63591 | [
-0.02985866367816925,
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0.03192916512489319,
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0.023441247642040253,
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0.035132184624671936,
0.05770520120859146,
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-0.030838288366794586,
0.016901584342122078,
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0.021286098286509514,
0... |
<p>Let $X_1, X_2, X_3 \sim N(0, d^2)$ and $T = X_1^2 + X_2^2 + X_3^2.$ </p>
<p>I have an estimator for $d$, $$\hat{d} = \frac{\sqrt{T\ 2\pi}}{4},$$
and another estimator for $d$, $$\tilde{d} = \frac{1}{3} \sqrt{\pi / 2}\ \left(|X_1| + |X_2| + |X_3|\right).$$</p>
<p>I need to show that $\mathbb{E}(\tilde{d} | T) = \ha... | g49820 | [
-0.016936220228672028,
-0.0073157064616680145,
-0.0327327698469162,
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0.011478042230010033,
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0.08359835296869278,
0.016485031694173813,
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0.08558446913957596,
0.0469086579978466,
0.0... |
<p>When running my analysis on a dataset, I find a positive Mantel-Haenszel chi square trend statistic. Does this mean that the trend in the data is positive or simply that there is a trend? The data deals with the improvement of patients' symptoms after taking a drug or a placebo. </p> | g63592 | [
-0.007005012594163418,
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0.011413863860070705,
0.06966937333345413,
... |
<p>I am using LibSVM library for classification. For my problem I am using polynomial kernel and I need to select best parameters (<code>d</code> = degree of polynomial kernel, and <code>C</code> = soft margin constant). The <a href="http://www.csie.ntu.edu.tw/~cjlin/papers/guide/guide.pdf" rel="nofollow">LibSVM guide<... | g645 | [
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0.03190632537007332,
0.04194524884223938,
0.0426940955221653,
0.02721305750310421,
0.03678... |
<p>If we draw two random variates from a discrete uniform distribution $[1, D]$, the probability that the samples are distinct is $(D-1)/D$. Explanations of the birthday problem state that if we sample a third time, the probability that this third sample is distinct from the first two is $(D-1)(D-2)/D^2$. Doesn't this ... | g47802 | [
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... |
<p>I am working on a text categorization task, and I possess 21,000 documents for training, and (for the time being), 7000 documents for testing. I construct the doc-term matrix for both training corpus and testing corpus, with two different weighting factors, i.e. <strong><em>TF</em></strong> (term frequency) or <stro... | g42192 | [
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<p>I am trying to create a variogram for a data set with 10,000 points. However, if I try to actually calculate the distance of each point with the other then I will have 10,000*9999/2 pairs. Out of these pairs of distances I can round off the distance values to lets say 2 decimal places. Then I can find the distances ... | g63593 | [
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<p>I would like to compare a handful of percentage values - whether they are significantly different from each other. Since the t-test only compares means, it doesn't seem appropriate. Multiple comparisons such as Scheffe's gave me a warning in SAS that only CLASS variables were accepted.</p>
<p>What kind of test shou... | g63594 | [
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... |
<p>I am not sure whether or not this problem can be solved through statistical methods, but here is the problem:</p>
<p>I have 4 professional reference providers for a job candidate rating the candidate on a scale of 0-100 on say 10 items. Behind the scenes we check for the consistency of ratings for each item from t... | g47915 | [
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<p>First of all, excuse me if this is not a good place to ask this question.</p>
<p>Can anyone explain to me how streaming kmeans algorithm implemented in Mahout works? And can it be used for anomaly detection?</p> | g63595 | [
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<p>I have basic knowledge on machine learning techniques and I'm working on a real-world regression problem which is basically predicting the time consumption of a certain task based on a number of predictor values. Unfortunately (as usual) the underlying relationship is not known to me.
However, I do assume that there... | g63596 | [
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... |
<p>I'm involved in a census at our condo association. We may, for logistics reasons, survey 1/4 of the population per quarter so that we have surveyed everyone by the end of the year, but let's assume we survey everyone at once.</p>
<p>A year later, we survey again. Since we're attempting to cover 100% of the populati... | g63597 | [
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<p>This image show a histogram (200 bins) of accumulated distances from a radar distance meter (very noisy).
The peak around 7 meters is an object. At thought this looked kind of like a normal distribution, at least if you ignore values <4m (which for this application is reasonable).</p>
<p>I have also achieved a r... | g40736 | [
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... |
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