question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>In a specification where negative binomial regressions are estimated, can the coefficients be interpreted directly as in the OLS case?</p> | g62937 | [
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<p>I've 2 different questions:</p>
<p><strong>A.</strong> Sample with n variables, while $n-1$ variables are in the range (0-1), and one of the variable is very high: $10^{1000}$. If I'll use bootstrap to estimate the mean, what bias will I get?</p>
<p><strong>B.</strong> Please help me to find the variance of the me... | g62938 | [
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<p>I have implemented the condensation algorithm in order to track a moving object in video sequences, however the predictive step does not work properly, so the samples moves excessively compared to the actual movement of the object.</p>
<p>Maybe I need to estimate more accurately the velocity of the object: how to e... | g39469 | [
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<p>I'm building a predictive model for a medical condition that happens in both men and women. Physicians have reported that in some cases for women, their menstrual history seems to be a risk factor, though epidemiologists haven't been able to verify this claim. My data includes information about female subjects' mens... | g48138 | [
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<p>what is the best way to categorize or even bin monthly gross income? As of now, the variable for income is numeric and continuous. I have seen many examples for annual income. Should I categorize variables into quartiles? The purpose would be to fit the transformed variable into a logistic regression. As of now, I d... | g35712 | [
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<p>How do I distinctly represent two data sets on the same scatter plot , to compare the p-value distributions of the genes using R packages?</p>
<p>The gene expression values and p-values (obtained by ANOVA) of the two datasets are:</p>
<pre><code>### data A
probes AG1 AG2 LR1 LR2
901 ... | g62939 | [
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<p>I reviewed an application based paper saying that applying PCA before applying ICA (using fastICA package). My question is that does ICA (fastICA) requires PCA to run at first?</p>
<p><a href="http://www.cc.gatech.edu/~isbell/reading/papers/draper_cviu03.pdf" rel="nofollow">This paper</a> mentioned that "it is also... | g62940 | [
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<p>I tried both Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) in order to classify me data. While LDA is much better than PCA, the results are not good enough.</p>
<p>Are there any other alternatives that I can use? </p>
<p>Thanks</p> | g27976 | [
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<p>So I am developing this application for rating books (think like IMDB for books) using relational database. </p>
<p><strong>Problem statement :</strong></p>
<p>Let's say book "<strong>A</strong>" deserves 8.5 in absolute sense. In case if A is the best book I have ever seen, I'll most probably rate it > 9.5 where... | g49657 | [
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<p>I was wondering if, when running a regression on panel data, clustered standard errors are already correcting for heteroskedasticity. Actually, I have run such a regression and detected heteroskedasticity. Since I used the pooled OLS model I have to cluster the standard errors anyway. Hence, I was hoping that I can ... | g10229 | [
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<p>I have an application where I get back the time to perform an operation, the times are in the interval <code>]0:inf[</code> and I have this crazy idea. Lets say I know the mean of my dataset. woule it makes sense to test for normal distribution on the interval <code>]ln_n(0):mean[</code> if below mean and <code>[mea... | g33181 | [
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<p>For example, for linear models, you take the p-value of the regression, and you deduce if the regression is or not significative. But with non linear models, in R, there isn't shown a p-value associated to a F-statistic, that say if the regression is or not significative. How can I know if a non linear model is sign... | g62941 | [
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<p>Kernel density estimator is given by
$$\hat{f}(x,h)=\frac{1}{nh}\sum_{i=1}^{n}K(\frac{x-X_{i}}{h})$$
where $X_1,...X_n$ i.i.d with some unknown density $f$, $h$ - bandwith,</p>
<p>$K$ - kernel function (
$\int_{-\infty}^{\infty}K(x)dx=1$,
$\int_{-\infty}^{\infty}K(x)xdx=0$,
$\int_{-\infty}^{\infty}K(x)x^2dx&l... | g62942 | [
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0.033... |
<p><img src="http://i.stack.imgur.com/bBDqg.png" alt="N=2762"></p>
<p><strong>N=2762</strong></p>
<p>I've been exploring a data set that seems to give rise to this kind of plot rather frequently. Would you say this is one population with a different than normal population? Or are two populations confounding the norma... | g62943 | [
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<p>I am interested in learning (and implementing) an alternative to polynomial interpolation. </p>
<p>However, I am having trouble finding a good description of how these methods work, how they relate, and how they compare.</p>
<p>I would appreciate your input on the pros/cons/conditions under which these methods or ... | g39499 | [
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<p>I'm trying to compute some p-values for samples from a distribution of sums of ~1000 random variables. The exact distribution of these random variables isn't known, but I have empirical estimates that I think are pretty accurate.</p>
<p>So far I've been using the central limit theorem to produce a normal approximat... | g62944 | [
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<p>I have two datasets in which I probably need to use the intraclass correlation coefficient, and I want to make sure I choose the right type.</p>
<p><strong>Dataset 1</strong>:
I had 20 randomly selected human subjects rate 50 faces based on their attractiveness on an ordinal scale from 1-5. Each subject rated the s... | g62945 | [
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<pre><code>firm float %9.0g firm ID
year float %9.0g year, 82-88
va float %9.0g value added in millions of lire
labor float %9.0g permanent employees at year end
capital float %9.0g ... | g49412 | [
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<p>I have treated two groups of 100 people with different treatments. I have pre-treatment and post-treatment data for most participants (as well as 1-month follow-up. I also have weekly data for some variables, but may or may not include those). About 10% of cases dropped out before post-treatment in one group and 30%... | g327 | [
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<p>I am new to econometrics and I am building my first econometric model. I ran the LM test on a univariate time series data of 12000 observations and got the following stats:</p>
<pre><code>Chi-squared = 458.5313, df = 12, p-value < 2.2e-16
</code></pre>
<p>Can I reject the null? Is there presence of ARCH effect... | g20324 | [
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<p>I have three variables, a factor (<code>c</code>) as the dependent variable and two ordinal independent variables (<code>a, b</code>). Each variable has five categories (<code>1,2,3,4,5</code>). Thus, I fitted a multinomial logistic regression (<code>testus</code>, see below) with the <code>car</code> package. Now I... | g62946 | [
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<p>Let $Z=(X+Y)/2$, where $X$ and $Y$ are independent normally-distributed random variables with known variances $\sigma^2_X$ and $\sigma^2_Y$ and unknown (and possibly different) means. Given a sample $x_1$ from $X$ and $y_1$ from $Y$, what is the minimum mean squared error estimator of the mean of $Z$? Is there a bia... | g20325 | [
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<p>In Bayesian statistics, it is often mentioned that the posterior distribution is intractable and thus approximate inference must be applied. What are the factors that cause this intractability? </p> | g20326 | [
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<p>I'm having trouble to fit and simulate a <code>gamma distribution</code> using the <code>fitdistr</code> function from the <code>MASS</code> package:</p>
<p>My data is <code>daily rainfall</code>, so i 'm adding <code>1</code> to all points to get rid the 0's:</p>
<pre><code>require(MASS)
rainfall = scan('daily_ra... | g20327 | [
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<p>Can I use <a href="http://en.wikipedia.org/wiki/Chauvenet%27s_criterion" rel="nofollow">Chauvenet's criterion</a> on set of observations where a normal distribution cannot be assumed? </p> | g62947 | [
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<blockquote>
<p>Alice is getting married tomorrow at an outdoor ceremony in a
beautiful garden. </p>
<p>In recent years, it has rained, on average, only 5 days in a year.
Alice is anxious about the weather for tomorrow and wishes to get the
weather prediction from a weather forecaster. </p>
<p>From th... | g20329 | [
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<p>This question was from my CAs. Nothing has been changed.</p>
<p>A local weatherman forecasts that there is a 65% chance of rain on the
coming Saturday and a 65% chance of rain on the Sunday immediately following that Saturday.
What can you conclude from the above weather forecast?<br>
Choose one of the followin... | g20330 | [
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<p>I am using path analysis to test hypotheses in my study. I have been told by a few people in passing that I can use manifest variables rather than latent variables as long as my reliabilities are high.
The Cronbach's alpha reliabilities of my constructs are 0.81, 0.88, 0.87, 0.90 and 0.92.<br>
I know in general, ab... | g20332 | [
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<p>Taking into consideration the <a href="http://random.mat.sbg.ac.at/tests/empirics/runs/" rel="nofollow">runs test</a> proposed by Knuth given a sample of pseudo-random numbers to test independence, and looking at this example:</p>
<pre><code>X = (5,4,1,7,2,3,6), which yields
S = (0,0,1,0,1,1)
</code></pre>
<p>I'm ... | g62948 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/1142/simple-algorithm-for-online-outlier-detection-of-a-generic-time-series">Simple algorithm for online outlier detection of a generic time series</a><br>
<a href="http://stats.stackexchange.com/questions/3... | g49496 | [
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<p>I have a study variable that is measured at the individual level and then aggregated and to the group level. My hypothesis testing is conducted at the group level.
I used an 8-item referent-shift measure of team psychological capital.</p>
<p>When calculating and reporting the coefficient alpha, should I be looking... | g62949 | [
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-0.009825024753808975,
0.027729474008083344,
-0.007950685918331146,
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0.02274511195719242,
0.0244398582726717,
0.015402041375637054,
-0.01809614896774292,
0.0... |
<p>I have a model with a ratio (percentage) as dependent variable. The denominator of this DV also changes from year-to-year. I remember that we should be more careful with ratios as DV but I'm a little rusty on the specific steps that should be taken in this situation.</p>
<p>Some suggest to transfer the ration into ... | g10237 | [
0.0035728386137634516,
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0.0038155922666192055,
0.0376049913465976... |
<p>Quite a newbie to this, any info or pointers are appreciated, but please be as precise as possible.</p>
<p>If I have a feature in general that was launched mainly to improve the user experience, but interested to understand if it also helps to boost the movie sales on the website pre and post launch (the feature wa... | g62950 | [
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<p>A large dataset with more than 100 variables including a target variable. A small portion of target = 1 cases are fraud or due to other errors. I want to identify these target = 1 cases, i.e. fraud or error.
Assuming most cases are good, I intend to use decision tree to classify cases. In one leaf with a high perce... | g4561 | [
0.013261786662042141,
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<p>I would like to ask for some advice on an analysis that I am doing at the moment. </p>
<p>The experiment: I ran an experiment with animals in which I subjected 15 pairs of individuals (one male and one female in each pair) to three olfactory tests: treatment 1, treatment 2, treatment 3. Each test procedure involved... | g20347 | [
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<p>I am trying to find the following: If $X\sim\mathrm{Exp}(1)$ and $Y\sim\mathrm{Exp}(2)$, what is the pdf of $Z=X+Y$?</p>
<p>I tried to use the convolution formula but am not sure what the limits of the integral are:</p>
<p>$$g(z) = \int_{0}^{z} 1 \cdot 2\cdot\exp(-1\cdot(y-x))\cdot\exp(-2x) \mathrm dx.$$ </p>
<p>... | g62951 | [
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0.03331746906042099,
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0.021988550201058388,
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0.... |
<p>I have pre- and post-treatment continuous data for a large number of variables that I am analyzing for treatment effect. Normally I would obtain the P values and then adjust them for multiple testing with a method such as Benajmini-Hochberg.</p>
<p>However, the statistical test that I am using is somewhat computati... | g62952 | [
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... |
<p>Suppose we have a random variable $X$ supported on $[0,1]$ from which we can draw samples. How can we come up with an unbiased estimate of the median of $X$? </p>
<p>We can, of course, generate some samples and take the sample median, but I understand this will not in general be unbiased. </p>
<p>Note: this questi... | g62953 | [
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<p>What is the difference between a finite population and an infinite one - when you are designing an experiment (sample/power and interpretation of the results)?</p>
<p>Say a company has a database of 20,000 customers. Given that a response to some stimulus is relatively small, and a meaningful minimum detectable dif... | g62954 | [
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<p>I applied number of methods of clustering, and I want to evaluate these different methods using Dunn index, in this method I have to calculate the distance among clusters and among points in clusters.</p>
<p>My question is: if my algorithm is clustering users depending on their sequences, i.e., each user has sequen... | g20351 | [
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... |
<p><strong>Assumptions / Context:</strong> Let's assume that I have data that can be modeled as a dynamic linear model. To estimate the parameters (e.g., covariance matrix of the state/system equation), I use a Gibbs sampling or other Markov Chain Monte Carlo procedure.</p>
<p><strong>Problem:</strong> The problem is ... | g62955 | [
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0... |
<p>I am interested in performing a regression on data on a population. This population causes events X and Y. I have monthly data for population, event X, and event Y. Do I need to change my variables X and Y into rates (X divided by population) before running the regression?</p>
<p>Some details about the model: the p... | g10243 | [
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<p>I'm implementing a permutation test for a test statistic with unknown distribution. Apart from my concrete situation (see below), I'd like to know first </p>
<ol>
<li>If and under what circumstances permutation tests might inflate the type I error, that is, in what kind of situations they may produce anti-conservat... | g104 | [
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0.012976284138858318,
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0.015019486658275127,
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... |
<p>There is a blind test that asks participants to distinguish Coke and Pepsi.
A participant will test 6 cups of drink and tell whether it was Coke or Pepsi.
Assuming that the participant can tell the difference between them, though not perfect,
if he judged that the first three were all Coke,
then he would think it ... | g39536 | [
0.00927015207707882,
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-0.0... |
<p>Given an IID normally distributed sample $X_1,...,X_n$ for $n$ small with mean $\mu$, standard deviation $\sigma$, sample mean $\overline{X}$ and sample standard deviation $s$ (the unbiased estimator form). I understand that</p>
<p>$$\frac{\overline{X} - \mu}{\frac{\sigma}{\sqrt{n}}} \sim N(0,1),$$</p>
<p>but I'm... | g20362 | [
0.04617811366915703,
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0.001044364064000547,
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0.018440784886479378,
0.006260151509195566,
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<p>I am currently working on my research and I have the following problem. I have conducted a CFA on all model variables and after deleting the troublesome items, the CFA yielded good fit indices. </p>
<p>However, when i conduct a structural equation modeling (with item-averaged composites of the resulting items), I h... | g20363 | [
0.009051940403878689,
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0.0015579669270664454,
0.03789791092276573,
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0.03660651668906212,
0.037... |
<p>I am confused. I don't understand the difference a ARMA and a GARCH process.. to me there are the same no ?</p>
<p>Here is the (G)ARCH process</p>
<p>$\sigma_t^2 =
\underbrace{
\underbrace{
\alpha_0
+ \sum_{i=1}^q \alpha_ir_{t-i}^2}
_{ARCH}
+ \sum_{i=1}^p\beta_i\sigma_{t-i}^2}
_{... | g20368 | [
0.05051503702998161,
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0.008682196028530598,
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0.015512100420892239,
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0.07902055233716965,
0.02412554807960987,
-0.00... |
<p>Can someone show me how to evaluate</p>
<p>$\int_{0}^{\infty} x^4 e^{-x^2/{\beta}^2}dx$?</p>
<p>I am working on verifying that a function is a pdf, and finding its expectation and variance. I want to be able to do it step-by-step, without just getting the answer from a CAS. Thanks in advance!</p> | g62956 | [
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0.05035777762532234,
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<p>I am using a Machine Learning package called <a href="http://orange.biolab.si/" rel="nofollow">Orange</a>. This software provides a Python interface and a visual programming GUI. I am using the GUI at present.</p>
<p>There were 48 original variables. I have been using the PCA widget for dimensionality reduction a... | g20369 | [
0.022383015602827072,
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0.008120749145746231,
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0.02308916114270687,
0.003296916838735342,
0.038... |
<p>I have performed LRT:</p>
<pre><code>> (lL1 <- logLik(mixedModel))
'log Lik.' -65435.99 (df=4)
> (lL2 <- logLik(linearModel<-lm(y~x)))
'log Lik.' -78234.86 (df=3)
> ((Delta <- as.numeric(lL2-lL1)))
[1] -12798.86
> pchisq(- 2 * Delta, 1, lower.tail = FALSE)
[1] 0
</code></pre>
<p>How can... | g62957 | [
0.001010656007565558,
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0.04852345958352089,
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0.04423513263463974,
0.09559536725282669,
0.02... |
<p>I'm running twin models in which I estimate additive genetic and environmental influences in a bivariate model, mixing continuous and ordinal measures.
In my model I estimated an overlap between E estimates (non shared environmental influences), which brings out the following output:</p>
<pre><code>ACE.Re[2,1] 3... | g62958 | [
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0.09066734462976456,
0.03684276342391968,
0.016162732616066933,
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-0.009145625866949558,
0.026291899383068085,
0.022225653752684593,
0.04791378602385521,
0.03308... |
<p>What does it mean to draw a number at random from a normal distribution? Why can't you just "draw" numbers at random? Why do you have to draw random numbers from a distribution?</p> | g62959 | [
-0.012001784518361092,
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<p>In some data set A, we have: household id, person id, age, sex, and then a simple binary <code>likes donuts / does not like donuts</code> variable.
In some other data set B, we have just household id, person id, age, and sex.</p>
<p>We have set up a regression in data set A with independent variables: age, sex, and... | g62960 | [
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0.009317809715867043,
0.07252097129821777,
0.02330861985683441,
0.0647... |
<p>I have a dataset that I have to perform a regression task. I split the dataset into 80% for training and 20% for validation.</p>
<pre><code>train.index <- sample(N.rows, N.rows * 4/5, F)
train.data <- data[train.index,]
val.data <- data[-train.index,]
</code></pre>
<p>I used the GBM in R which has the par... | g62961 | [
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0.021367494016885757,
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-0.0021176873706281185,
0.016041889786720276,
0.02918098308146,
0.05032386630773544,
0.0069... |
<p>I have a distribution which looks a bit binomial, though with a cutoff, i.e.:</p>
<p>$P(x) = 0$ if $x \le 0$, rises to a bell-shaped peak at around $x=0.2%$, appears to tail off exponentially until an abrubt cut such that $P(x)=0 $ if $x>1$.</p>
<p>I don't want to make any claim as to what kind of distribution ... | g20375 | [
0.009270254522562027,
0.06557232141494751,
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0.029896149411797523,
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-0.023072179406881332,
-0.0016065113013610244,
0.03760862722992897,
0.0741616040468216,
-0.0... |
<p>I frequently used to diagnose my multivariate data using PCA (omics data with hundreds of thousands of variables and dozens or hundreds of samples). The data often come from experiments with several categorical independent variables defining some groups, and I often have to go through a few components before I can f... | g62962 | [
-0.008640707470476627,
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-0.04249070584774017,
0.04370326176285744,
0.04178575053811073,
0.04404653608798981,
-0.01... |
<p>My data consists of occurrences of words in time windows. E.g.:</p>
<pre><code>Day; Word; Frequency
1; "dog"; 45
1; "cat"; 2
...
2; "dog"; 90
2; "cat"; 4
...
</code></pre>
<p>I would like to estimate the ratios of all day-to-day differences (i.e., for dog day 1->2: 90-45/45 = 100%). For cat the increase is also 10... | g62963 | [
-0.021745456382632256,
0.0021042730659246445,
-0.02294549159705639,
-0.07541362196207047,
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0.0162521842867136,
0.001885571051388979,
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0.016895748674869537,
0.048655327409505844,
-0.00036903825821354985,
0.036704640835523605,
... |
<p>Why should the importance density (or biasing density) $g$ have heavier tails than the original distribution $f$? </p>
<p>Equivalently, why should</p>
<p>$$\frac{f(x)}{g(x)}<M , \forall x$$ for some $M>0$?</p> | g62964 | [
0.06723825633525848,
0.010888203047215939,
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-0.04034886136651039,
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0.025699900463223457,
0.04836577549576759,
0.0162... |
<p>I have measured total organic carbon (TOC), total nitrogen (TN) and chlorophyll content in seawater at two depths i.e. upper and lower. </p>
<p>Now I want to do statistical analysis of my data to compare the relation between the three - whether they are related or unrelated, whether they affect one another signific... | g62965 | [
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0.022584104910492897,
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0.0368993915617466,
0.007665582466870546,
0.0329320952296257,
0.0172053... |
<p>What are good examples to show that, even if a regression of $Y$ on $X$ is heteroscedastic, a regression of $Y$ on a different independent variable $Z$ could be homoscedastic?</p>
<p>More formally, what are populations of triples $(Y_i, X_i, Z_i)$ for which all of the following hold:</p>
<p>a) $E[Y_i | X_i]$ is an... | g62966 | [
-0.03189491108059883,
0.032613325864076614,
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0.02171284891664982,
0.022525612264871597,
0.0028704286087304354,
0.038633793592453,
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0.016392329707741737,
0.010089721530675888,
-0.0365428701043129,
0.02026774361729622,
0.07044766843318939,
0.0193303... |
<p>I am trying to predict auction prices from a self gathered data set.</p>
<p>I have titles available, and the price it was offered for. Now I noticed that whenever there is a 3 digit string of numbers in the title, there is about 48% that this is the actual price offered (I constrained to only gather data of the pri... | g62967 | [
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0.010540955699980259,
0.010089565999805927,
0.05236669257283211,
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-0.01864352449774742,
-0.022089404985308647,
0.04277126118540764,
0.059866711497306824,
-0.... |
<p>I am currently implementing a simple neural network and the backprop algorithm in <strong>Python</strong> with <strong>numpy</strong>. I have already tested my backprop method using central differences and the resulting gradient is equal.</p>
<p>However, the network fails to approximate a simple sine curve. The net... | g22559 | [
0.012862682342529297,
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0.0469632... |
<p>I have a Poisson GLM model</p>
<pre><code>m1 <- glm(count ~ x, data = data, family = "quasipoisson")
</code></pre>
<p>The predictor variable x is a cumulative sum of ratios, i.e. real numbers between 0 and 1. (Not important for this question, but if you are interested why the sum is needed, it is because it is ... | g62968 | [
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<p>a friend of mine has asked me to help him with predictive modelling of car traffic in a medium sized parking garage. The garage has its busy and easy days, its peak hours, dead hours opening hours (it is opened during 12 hours during weekdays and during 8 hours during weekends). </p>
<p>The goal is to predict how m... | g20379 | [
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<p>I have a logistic regression model: $softmax(WX)$ where $W$ is my parameter matrix and $X$ is my input. I want a density function over the outputs of that model.</p>
<p>Say I know that my $X$ are distributed according to some density $p$. From the <a href="http://en.wikipedia.org/wiki/Probability_density_function#D... | g20380 | [
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<p>What book is the most thorough treatment of fundamental concepts in statistics?
I am not asking for a book on details of the methods of calculations and procedures, I am mainly interested in a book that thoroughly explains the foundational concepts ... an intuitive/illustrated/visual approach to the core ideas ... ... | g49639 | [
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<p>I have the following experimental layout:</p>
<ol>
<li><p>five different treatments - harvesting rates, ranging from 0 to 1, indicating proportion of branches per plant harvested</p></li>
<li><p>75 plants, randomly assigned plants to each treatment, resulting in 15 plants per treatment</p></li>
<li><p>followed over... | g39581 | [
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<p>I'm analyzing a certain dataset, and I need to understand how to choose the best model that fits my data. I'm using R.</p>
<p>An example of data I have is the following:</p>
<pre><code>corr <- c(0, 0, 10, 50, 70, 100, 100, 100, 90, 100, 100)
</code></pre>
<p>These numbers correspond to the percentage of correc... | g62969 | [
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<p>I have this data:</p>
<pre><code>DAY # of units Manuf %
1 800 20
2 400 10
3 1200 30
4 800 20
5 400 10
6 200 5
7 200 5
</code></pre>
<ul>
<li>First column is day of week.</li>
<l... | g62970 | [
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... |
<p>I have some SKUs and I'd like to do a forecast using single exponential smoothing as a forecasting method, when should we go for small value of alpha (.05,.1,...) and when for bigger values(.8,.9,...)? Does it depend on the characteristics of the series? </p> | g62971 | [
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<p>The AIC is defined as $AIC=-2 \log(L(\hat\theta))+2p$, where $\hat\theta$ is the maximum likelihood estimator and $p$ is the dimension of the parameter space. For the estimation of $\theta$, one usually neglects the constant factor of the density. This is, the factor that does not depend on the parameters, in order ... | g62972 | [
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<p>If you've been reading the community bulletins lately, you've likely seen <a href="http://blog.stackoverflow.com/2012/07/the-hunting-of-the-snark/?cb=1">The Hunting of the Snark,</a> a post on the official StackExchange blog by Joel Spolsky, <a href="http://en.wikipedia.org/wiki/Joel_Spolsky" rel="nofollow">the CEO ... | g62973 | [
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<p>I have a question about the shape of the error surface for online gradient descent algorithms. Take into account that I am trying to translate my specific question into a more general and idealized situation so that you can understand it. This means that the situation and constraints you will read here may look a bi... | g20386 | [
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0.... |
<p>I am using R's <a href="http://www.spatstat.org/spatstat/" rel="nofollow">package spatstat</a> to study the locational pattern of conflict events in Africa (around 8.000 points) using point pattern analysis techniques.</p>
<p>I was able to obtain the plot of g(r), the pair correlation function, using the contour of... | g20387 | [
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<p>I'm using libsvm in C-SVC mode with a polynomial kernel of degree 2 and I'm required to train multiple SVMs. Each training set has 10 features and 5000 vectors. During training, I am getting this warning for most of the SVMs that I train:</p>
<pre><code>WARNING: reaching max number of iterations
optimization finish... | g39584 | [
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0.03133774548768997,
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0.028514230623841286,
0.03918147087097168,
0.0718... |
<p>I am using the train function in caret package. I have 55 predictors and a continuous outcome. The model that I selected is glmnet. Looking the results of using the "predictors" function-just to check what variables are involved in the final model- it seems that 29 out off 55 variables are taking part in the model. ... | g62974 | [
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0.0... |
<p>I have a monthly time series of a water quality parameter. I used copula-based Markov process of C(Y(t), Y(t-1) and I forecasted the mean behavior of Yt by following equation:
<img src="http://i.stack.imgur.com/pGjBe.jpg" alt="enter image description here"> </p>
<p>Now, I need to find the probability that for a gi... | g62975 | [
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0.05115290731191635,
0.0... |
<p>I'd like to check in R if my data fits log-normal or Pareto distributions. How could I do that? Perhaps ks.test could help me do that, but how could I get the alpha and k parameters for Pareto distribution for my data? Any help will be appreciated.</p> | g20393 | [
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0.017739659175276756,
... |
<p>Let say we have only one sample in which we are interested only on one statistics c of this sample. This is usually true in practice when we usually have only one data set. So, most probably the usual estimating method like MLE cant be applied.</p>
<p>And let say we want to estimate 2 parameters (i.e. a & b) of... | g62976 | [
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0.018094569444656372,
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0.... |
<p>So I am using SPSS, but not sure what analysis to run if I am trying to determine if there is any difference between pre-post survey results in one group. So basically I have a group that has pre-post test results and I want to compare both pre-post within that same group. All my variables are categorical. </p> | g49887 | [
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... |
<p>I have conducted an intervention study on preschool children on behavior problems, social-emotional competence with control and experimental groups. I have analysed the results using ANCOVA to find out main intervention effects on measures. Now I want to see if there are any gender differences in intervention group ... | g62977 | [
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0.0... |
<p>For a linear regression with multiple groups (natural groups defined a priori) is it acceptable to run two different models on the same data set to answer the following two questions?</p>
<ol>
<li><p>Does each group have a non-zero slope and non-zero intercept and what are the parameters for each within group regre... | g62978 | [
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0.05135761573910713,
0.012596195563673973,
0.009603512473404408,
0... |
<p>How do I know when to choose between Spearman's $\rho$ and Pearson's $r$? My variable includes satisfaction and the scores were interpreted using the sum of the scores. However, these scores could also be ranked. </p> | g49569 | [
0.033653371036052704,
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0.024424953386187553,
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0.06280869990587234,
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<p>I am performing a longitudinal analysis and I am curious if the predictors we are including in the model will introduce any unexpected effects. </p>
<p>We have subjects with multiple points of follow-up and they are entered into the study at various times and ages. The main hypothesis we want to test is if there ... | g62979 | [
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0.025002682581543922,
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0.022270629182457924,
... |
<p>I am assessing a bunch of classification algorithms for a specific application with multiple classes. The classification algorithms that I am considering are:</p>
<ol>
<li>Multinomial Logistic Regression (Matlab's 'mnrfit')</li>
<li>Multiclass SVM (K. Crammer and Y. Singer. On the Algorithmic Implementation of Mult... | g7601 | [
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0.001775776850990951,
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0.... |
<p>If I want to achieve a margin-of-error of <= 5 % for a representative population sample, how large a sample do I need when: The interviewees are picked from <em>X</em> regions and from <em>Y</em> age groups? That is, how many samples from each age group & region?</p>
<p>I know how many people live in each re... | g37522 | [
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0.03795167803764343,
0.0... |
<p>My dependent variable is not normally distributed. I chose the Gamma log link, and I hope this is correct. I wasn't entirely sure with this because the dependent variable is actually a whole lot of percentages. I know this isn't technically continuous, but if I choose Poisson, it excludes most of my data. so questio... | g62980 | [
0.0029122454579919577,
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... |
<p>A colleague and I have been clustering some data in SPSS (v19) and R (2.15), respectively. Using the same distance metric and agglomeration method, we get identical merge orders/agglomeration schedules in both programs, and the dendrograms have very similar shapes, but the actual height values are quite different. O... | g39593 | [
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0.10524088889360428,
... |
<p>It is easy to compare <em>paired</em> data, using paired t-test. But suppose this pairing is hierarchical. Below is an example:</p>
<p>The stem cells of two mouse strains S1 and S2 are cultured in two different culture conditions C1 and C2, having 3 replicates for each Strain/Condition (2 x 2 x 3 = 12 samples total... | g62981 | [
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0.01735386624932289,
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0.06523437052965164,
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0.... |
<p>I want to create forecasting for a large quantity of time series. Since they are too many, I am thinking on reducing my data by clustering it into to similar groups. However, I am using SPSS modeler and it is not possible to cluster time series (only static data). </p>
<p>Do you think it makes sense to apply cluste... | g62982 | [
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<p>Many of my colleagues are considering using the M-PLUS package to carry out Hierarchical Linear Modeling, rather than the HLM 7 package. Both packages are designed by very well respected figures in the field of Hierachical Linear Modeling. Have any users seen distinct statistical advantages in using one package or... | g62983 | [
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<p>I am familiar with linear regression models but the random section of linear mixed models just melts my mind. I did find an excellent guide that could have helped me but the languageR package is not compatible with newer versions of lme4 so I've been unable to implement it in my work.</p>
<p>For me the fixed effect... | g39595 | [
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0.016955988481640816,
0.... |
<p>I'm up to perform certain kinds of sparse decomposition methods on my dataset. However, I'm not sure: what's the tractable data size for the Sparse Decomposition methods?</p>
<p>The dataset is a $10^3\times10^5$ binary matrix, and the expected methods are Sparse PCA, which aims to find a decomposition with minimize... | g62984 | [
0.01656375266611576,
-0.0010979705257341266,
-0.0035290587693452835,
-0.05395479500293732,
0.016731321811676025,
-0.10014838725328445,
0.020921191200613976,
0.014610331505537033,
-0.06519606709480286,
-0.029727650806307793,
0.030996937304735184,
-0.03484299033880234,
-0.022324755787849426,
... |
<p>I am working on an e-learning system with a friend for our final year (Computer Science) project which is part of the under-graduate programs mandatory 'courses'.</p>
<p>I have a question about making inferences and therefore gauging the skill level of the 'subject (student) at hand'</p>
<p>We have gathered the fo... | g62985 | [
-0.02702852338552475,
-0.025757601484656334,
-0.010988316498696804,
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0.042382728308439255,
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-0.005110747646540403,
0.016285067424178123,
0.02026352286338806,
0.09167442470788956,
0.... |
<p>I am testing a product (liquid bag) for leakage and my primary variable is the amount of leakage in ml. I have a specification that states, on average, leakage must be below XXml. In total I tested 20 bags. Now my problem is this: none of the bags leaked so essentially my data consists of 20 values all equal to zero... | g62986 | [
0.021976597607135773,
-0.019334515556693077,
0.00047281323350034654,
-0.04707321524620056,
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0.... |
<p>I have an assignment to implement the <a href="http://en.wikipedia.org/wiki/Adaptive_resonance_theory" rel="nofollow">adaptive resonance theory</a> (ART) type network (as part of a bigger project). I have red a lot of Internet resources on the topic and I think I've got the essence of it, but I am not sure. So far I... | g62987 | [
-0.026427533477544785,
-0.026518728584051132,
-0.013737427070736885,
-0.031819142401218414,
0.0429956279695034,
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0.07115872204303741,
0.034249935299158096,
-0.044178981333971024,
-0.006123694591224194,
-0.03127617761492729,
-0.0036397355142980814,
0.037958335131406784,
... |
<p>I have carried out some research on whether awareness and knowledge of HIV had been increased on university students by giving a questionnaire to students before and after a presentation on HIV. Only 140 students completed the pre questionnaire and only 129 completed the post questionnaire after the presentation. So... | g62988 | [
-0.02666069194674492,
-0.018543291836977005,
0.0035532561596482992,
-0.03251522034406662,
-0.0021249966230243444,
-0.011137666180729866,
0.013675779104232788,
0.023433996364474297,
0.010989831760525703,
-0.006135332863777876,
-0.009254018776118755,
0.024636905640363693,
0.026435909792780876,... |
<p>Given $X\sim N(0,\Omega)$. Suppose that we can construct a sequence $\{X_n\}$ based on the observation such that $\{X_n\}\to X$ in distribution. My problem is to estimate $\Omega$ consistently using this sequence.</p>
<p>If $\operatorname{var} X_n$ converges to a "finite" matrix, then of course $\operatorname{var}X... | g62989 | [
-0.01778576523065567,
-0.018520142883062363,
-0.010177633725106716,
-0.019735127687454224,
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0.029804175719618797,
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0.005228305701166391,
-0.011981888674199581,
... |
<p>Suppose that, for year $t$, the data $y$ is Poisson with mean $a + bt$. Assume also a uniform prior on $(a,b)$. If we have $n$ years of data then I think the posterior for $(a,b)$ will be</p>
<p>\begin{align*}
p(a,b | y) &\propto p(y|a,b)p(a,b) \\
&\propto p(y | a, a) \\
&=\prod_{i=1}^n {\rm Po... | g62990 | [
0.00941452570259571,
-0.019779980182647705,
-0.010482455603778362,
-0.101028211414814,
-0.024367783218622208,
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0.03003719449043274,
-0.02042297273874283,
0.046106476336717606,
-0.001652815262787044,
-... |
<p>I have two sets of random data $X=\{x_1,...,x_N\}$ and $Y\{y_1,...,y_N\}$ both of length $N$. The sets are autocorrelated such that the correlation between $x_i$ and $x_j$ depends only on $|i-j|$. From both of these I can find the sample mean,
$$
\bar{X} = \frac{1}{N}\sum_{i=1}^N x_i
$$
and similarly for $Y$. I b... | g62991 | [
0.000006409453817468602,
-0.03088872693479061,
-0.01352251973003149,
-0.026072481647133827,
0.024429891258478165,
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0.047428980469703674,
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-0.04970542713999748,
-0.005821368657052517,
0.08202812075614929,
-0.024147192016243935... |
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