question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I would like to construct CIs for $\beta$ in the linear model</p>
<p>$Y = X\beta + \epsilon$</p>
<p>I observe $\{X', Y'\}$ which is $\{X,Y\}$ contaminated with values missing at random. $\epsilon$ is not Gaussian and not homoscedastic.</p>
<p>I propose to construct CIs for $\beta$ by:</p>
<ol>
<li>Generating sev... | g43981 | [
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<p>Lets say I'm doing 10,000 flips of a coin. I would like to know the probability of how many flips it takes to get 4 or more consecutive heads in a row. </p>
<p>The count would work as the following, you would count one successive round of flips being only heads (4 heads or more). When a tails hits and breaks the st... | g39648 | [
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<p>My datasets have two classes A and B. The classes should be treated equally (there is no "active/inactive"). The datasets are unbalanced, sometimes A is more frequent, sometimes B is more frequent. Which performance measure should I use?</p>
<p>Accuracy makes no sense on unbalanced datasets. If I get it right, F-me... | g71535 | [
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<p>I have problem about the assumptions and model verification of ARIMA models. I know that Gaussian distributed assumption is not necessary for fitting ARIMA models but I wonder why a lot of people standardize their data before fitting an ARIMA and why we check the residuals for being white Gaussian?</p> | g33052 | [
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<p>I'm trying to figure out the origin of the finite population correction (FPC) factor. That is, who developed it as a concept and theory, and when was it first documented.</p>
<p>I realize this is a tricky question. The history of certain basic ideas in statistics is quite complicated (see <a href="http://rads.stack... | g71536 | [
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<p>There exist <a href="http://en.wikipedia.org/wiki/Statistical_distance" rel="nofollow">a number of tools</a> that provide a distance between two continuous probability distributions. Most (semi)distances, like the Kullback-Leibler divergence, use probability density functions. However, the literature is quite sparse... | g71537 | [
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<pre><code>W = 0
for p in xrange(10):
W += -2*log(0.5)
print "W:",W
final_p = 1 - scipy.stats.chi2.cdf(W, 2*10)
print "Final p-value",final_p
</code></pre>
<p>Why does this result in a final p-value of 0.837376439136, when I used only the most insignificant p_values (p=0.5 for the null hypothesis)? Shouldn't this ... | g33054 | [
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<p>Using their previous results and the results form an aptitude test, students are given a target score. This score is a decimal number between $0$ and $120$. After their final exams they are graded on the same scale (although they receive a letter corresponding to intervals).</p>
<p>I would like to devise a statisti... | g71538 | [
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<p>I'm reading a paper that says that the authors used "bagged random forests". I couldn't understand this because as far as I know a random forest is a kind of bagging on its own. So a random forest is a bag of trees. But a bagged random forest?! Would that mean a bag of random forests with each random forest having 1... | g71539 | [
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<p>I need to analyze three samples of molecular barcodes, two from blood and one from tissue. My question is which of the two blood samples is more similar to the tissue in terms of molecular barcodes.</p>
<p>The number of unique barcodes in sample BLOOD-A is 3,000, in sample BLOOD-B is 20,000, and in TISSUE is 10,000... | g33057 | [
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<p>I would appreciate if someone could help me write the mathematical equation for the seasonal ARIMA (0,0,5) x (1,0,1) period 12. I'm a little confused with how to go about this. </p> | g49876 | [
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<p>I need to compute the <strong>Dirichlet CDF</strong>, but I can only find implementations of the <strong>PDF</strong>. </p>
<p>Do you guys know of any library (preferably in <code>R</code>) implementing it?</p> | g43989 | [
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<p>I'm currently adapting a coping questionnaire which has been widely used in sports to be used with a different population (musicians), so I need to address its <strong>reliability</strong> and <strong>validity</strong> with this new population. I'm a novice in statistics therefore any advice will be very helpful.</p... | g71540 | [
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<p>I'm using the Fligner-Killen test to analyze the residuals of a linear regression.
I subdivide those residuals in three groups and then I do the FK test to check the homogeneity of variances.</p>
<p>The result is:</p>
<pre><code>fligner.test(pair.res, pair.groups)
Fligner-Killeen test of homogeneity of varian... | g71541 | [
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-... |
<p>I performed and plotted a kmeans analysis in R with the following commands:</p>
<pre><code> km = kmeans(t(mat2), centers = 4)
plotcluster(t(mat2), km$cluster) #from library(fpc)
</code></pre>
<p>Here is the result from the plot: <img src="http://i.stack.imgur.com/p3ds0.png" alt="kmeans clustering"></p>
<p>T... | g71542 | [
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<p>Hopefully someone on these forums can help me out with this basic problem in gene expression studies.</p>
<p>I did deep sequencing of an experimental and a control tissue. I then obtained fold enrichment values of genes in the experimental sample over control. The reference genome has ~15,000 genes. 3,000 out of 15... | g71543 | [
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<p>I want to know about Mahout's implementation of classification algorithms - how does its accuracy compare with other large data software?</p>
<p>Anyone knows a reference on this?</p>
<p>I know about this SAS Report: <a href="https://support.sas.com/resources/papers/Benchmark_R_Mahout_SAS.pdf" rel="nofollow">https:... | g27957 | [
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<p>This is a very basic question (I'm currently studying undergrad level statistics), but I was hoping for some clarification regarding an assertion I read in <a href="http://www.guardian.co.uk/lifeandstyle/2013/mar/10/alice-roberts-on-science-childbirth-risks" rel="nofollow">a newspaper article</a> earlier today. The ... | g43999 | [
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<p>I work at a hospital and have been asked to use statistical algorithms to identify an increase in Census which is really the number of patient days in a hospital. It has trended up about 15 percent in the past three months and we have not been able to identify why using basic descriptive statistics. I have dozens of... | g71544 | [
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<p>I used centering for my variables due to multicolleanirity and surprisingly the results (from before to after centering) changed for two interacted variables; one from significantly negative to significantly positive and the other from significantly positive to significantly negative.
I read that results normally ch... | g33068 | [
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<p>This is a practice problem for a midterm exam. The problem is an EM algorithm example. I am having trouble with part (f). I list parts (a)-(e) for completion and in case I made a mistake earlier.</p>
<p>Let $X_1,\ldots,X_n$ be independent exponential random variables with rate $\theta$. Unfortunately, the actual $X... | g71545 | [
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<p>I mean by sphericity the assumption that the variance of all pairwise differences should be the same between groups.</p>
<p>In particular, I don't understand why this should be the assumption and not that the variances of the group scores themselves be the same.</p> | g71546 | [
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<p>Studying the asymptotic distribution of order statistics I came across this approximation:</p>
<p>$$F \left( E \left[ Y_n^{\left(n \right)} \right] \right) \approx E \left[ F \left( (Y_n^{\left( n \right)} \right) \right] $$ </p>
<p>where $Y_n^{\left( n \right) }$ denotes the sequence of the nth order statistics a... | g71547 | [
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<p>I am reading up on the Cramér-Chernoff method in concentration inequalities. The idea is to use Markov's inequality and the monotonic transformation $\phi(t) = e^{\lambda t}$ where $\lambda \geq 0$.</p>
<p>Consider a non-negative random variable $Z$ with finite expectation. Then Markov's inequality implies
$$ (1) \... | g71548 | [
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<p>In the Coursera NLP course , Dan Jurafsky calculates the following perplexity:</p>
<p>Operator(1 in 4)
Sales(1 in 4)
Technical Support(1 in 4)
30,000 names(1 in 120,000 each)
He says the Perplexity is 53. </p>
<p>The lecture can be found here: <a href="https://class.coursera.org/nlp/lecture/129" rel="nofollow">htt... | g71549 | [
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<p>I understand that the <a href="http://en.wikipedia.org/wiki/Jeffreys_prior" rel="nofollow">Jeffreys prior</a> provides a method for constructing a prior distribution over parameters for a given model (likelihood function) such that the prior distribution is "invariant under reparameterization." I understand this inv... | g957 | [
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<p>I have a series of three dimensional data like so:</p>
<pre><code> 1 2 3 4 5
1 0 0 0 0 0
2 0 0.3 0.5 0.3 0
3 0 0.5 1.0 0.5 0
4 0 0.3 0.5 0.3 0
5 0 0 0 0 0
</code></pre>
<p>Which is clearly a normal distribution. I want some way to ... | g48347 | [
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<p>Is there any reference or guideline regarding the minimum number of studies for conducting a meta-analysis?</p> | g71550 | [
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<p>Suppose I have two samples with the following statistics and I want to determine if there is a difference in their means.</p>
<p>First:</p>
<pre><code> Min. 1st Qu. Median Mean 3rd Qu. Max.
0.0 39.0 39.0 38.6 40.0 48.0
</code></pre>
<p>Others:</p>
<pre><code> Min. 1st Qu. Median ... | g33073 | [
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<p>I am running simulations to compare different weighting methods to estimate the mean of y (with missing values). I use bias, RMSE and 95% CI Coverage as my performance metrics. However, looking at RMSE and coverage, I arrive at different conclusions. For example, for method A and B, bias(x10^3) are 75 and -134 respe... | g16998 | [
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0.03923... |
<p>In Bayesian decision theory: Given $\omega_1$ and $\omega_2$ as two classes for classification, $P\left( \omega_1 \right)$ and $P\left( \omega_2\right)$ their prior probabilities, $x$ the feature vector representing an unknown pattern, $P\left( \omega_1 | x\right)$ and $P\left( \omega_2 | x\right)$ as posteriori pro... | g71551 | [
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0.030092669650912285,
0.01666785217821598,
0.02682056464254856,
0.039505716413259506,
0.02285158634185791,
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-0.010391924530267715,
0.01965573988854885,
0.044614098966121674,
0.049569498747587204,
0.06642... |
<p>I hope someone her can help me because I'm so lost. I'm trying to figure out what statistical test I should use for my study:</p>
<p>I want to look at how promotions, stadium age, and environmental sustainability impact attendance at sporting events. What statistical test should I use? If someone could help me I'd ... | g33078 | [
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<p>I'm familiar with the diagnostics required for OLS, however I'm in new territory with a model I'm fitting to data in R, using Poisson regression with GLM.</p>
<p>What are the standard methods in evaluating a WLS model?</p> | g71552 | [
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<p>I would like to know if there is a difference in the values taken from measurements of a given characteristic sampled at primary <code>forest=1</code> and secondary <code>forest=0</code></p>
<p>I'm using two vectors, one with the data itself (<code>DATA$Measurements</code>), and the other one with the category of s... | g49877 | [
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<p>I am sick of using the examples in the book. Is there an easy place to find data for which z-score/percentile/normal distribution stuff would be easy to see?</p> | g71553 | [
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<p>I've run across a couple guides suggesting that I use R's nlm for maximum likelihood estimation. But none of them (including <a href="http://stat.ethz.ch/R-manual/R-devel/library/stats/html/nlm.html">R's documentation</a>) gives much theoretical guidance for when to use or not use the function.</p>
<p>As far as I ... | g71554 | [
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0.072... |
<p>Similar to this question: <a href="http://stats.stackexchange.com/questions/63600/how-to-translate-the-results-from-lm-to-an-equation">How to translate the results from lm() to an equation?</a> in which the top voted answer said how to get the form of an equation from <code>lm(y ~ x)</code> and equivalently for <cod... | g33081 | [
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<p>I have 150 observations, 500 features, and I am interested in novelty detection (outlier detection): given a new observation (let's say 'patient') I want to know if it is different from the previous ones (let's call it 'control'). If I had a lot of data, I would probably be using statistical testing at the univariat... | g44015 | [
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<p>This is a statistical version of my <a href="http://math.stackexchange.com/questions/30731/will-two-convex-hulls-overlap" >Math.SE </a> post.</p>
<p>Given natural numbers $b$ and $r$, uniformly randomly choose $b+r$ points within a unit square. Call the $b$ points the <i>blue points</i> and the $r$ points <i> red p... | g33083 | [
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<p>The problem I am trying to solve is finding the probability that two people are the same by cross-referencing the associates of the two people. For example, if person A is associated with the following people:</p>
<ul>
<li>Jeff</li>
<li>Rick</li>
<li>Jessica</li>
<li>Mary</li>
</ul>
<p>Person B is associated with ... | g33084 | [
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<p>After doing some reading on CrossValidated, I understood that we can use "imputation" techniques to fill in the gaps (if they are random). But I am not clear on following questions:</p>
<ol>
<li><p>How many consecutive gaps may make data set invalid for forecasting?</p></li>
<li><p>How many total gaps in data set m... | g71555 | [
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<p>I have 3 algorithms (A, B, C) which predict "author name" of each text article. I have tested all the algorithms on 3 different corpora (X, Y, Z) (different number of articles from 3 newspapers). I have got the following result.</p>
<p>The result provides the number of "Correct" and "Incorrect" answers and the "Acc... | g71556 | [
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<p>I am currently running quasipoisson models with a continuous response variable and 13 covariates. I am using <code>glm()</code> and <code>summary()</code>. Most of my covariates are continuous but I also have the <code>YEAR</code> and <code>SEASON</code> as categorical variables. </p>
<p>When I run the model it app... | g33086 | [
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<p>I was reading a paper where they showed that when $\mathbf{X}$ and $\mathbf{Z}$ are two multidimensional variables</p>
<p>$$p(z_{nk}=1|\mathbf{X}, \mathbf{Z}_{\neg nk})\propto p(\mathbf{X}|\mathbf{Z})p(z_{nk}=1|\mathbf{Z}_{\neg nk}).$$</p>
<p>I didn't get how this expression was obtained. Suggestions?</p> | g71557 | [
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<p><img src="http://i.stack.imgur.com/yc6o9.png" alt="enter image description here"></p>
<p>Histogram showing the frequency for test scores (range 15-75) for a total of 91 students.</p> | g28990 | [
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<blockquote>
<p>If $X_1, ... , X_n$ be iid exponential with mean $1/\lambda$. Let $S_n = X_1 + ... + X_n$.</p>
<p>a) Show that $S_n$ is $\Gamma(n, 1/\lambda)$. </p>
</blockquote>
<p>Each $X_i$ is $\Gamma(1, 1/\lambda)$ by the definition of an exponential distribution. We can look at the mgf of $S_n$. </p>
<p>$... | g33088 | [
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<p>Let's say I have monthly data on cars on the road and number of car accidents. I want to know whether cars on the road is somehow related to the number of car accidents. Of course, I could conduct regression analysis or correlation analysis. However, when I have a set of 50 or so months with the number of cars on th... | g71558 | [
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<p>In a Hamiltonian system, the Hamiltonian is always preserved, but in HMC algorithm, new state is accepted by probability $\min(1,\frac{\exp(-H_{new})}{\exp(-H)})$, I think increase or decrease in Hamiltonian is due to numerical error, why should we always prefer a state with low Hamiltonian while what we actually wa... | g14469 | [
0.08700364828109741,
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<p>I have two distributions: A, and B. Each distribution is filled with the numbers 1.0-10.0. These distributions are NOT simple functions, like the gaussian, but are merely empirical counts.</p>
<p>Essentially, I want to create a model for the probability that any given number is A.
You can imagine that this is easy... | g71559 | [
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<p>Have 4 groups of results from 4 different treatments. Want to compare pre- and post treatment within groups and between groups</p> | g2060 | [
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<p>Is it right that both Cramér's $\phi_{c}$ (and consequently <a href="https://en.wikipedia.org/wiki/Cram%C3%A9r%27s_V" rel="nofollow">Cramér's $V$</a> as well) are similar to the <a href="https://en.wikipedia.org/wiki/Pearson_product-moment_correlation_coefficient" rel="nofollow">Pearson correlation coefficient</a>, ... | g71560 | [
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0.007880514487624168,
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... |
<p>I'm trying to perform a knn regression on a sales time series using the kknn package. I can't see how you can restrict the neighbours to past sales only though.</p>
<p>e.g.</p>
<pre><code>Product, Price, Sale Date
A, £100, 2012-01-04
A, £100, 2012-01-05
A, £200, 2012-01-06
</code></pre>
<p>If... | g71561 | [
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0.006858637556433678,
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<p>Can anyone provide or point me to a freely available implemention of Elastic Net in C or C++?</p> | g39939 | [
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0.024312244728207588,
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<p>As an example, consider the <code>ChickWeight</code> data set in R. The variance obviously grows over time, so if I use a simple linear regression like:</p>
<pre><code>m <- lm(weight ~ Time*Diet, data=ChickWeight)
</code></pre>
<p>which aspects of the model will be questionable? Are the problems limited to extr... | g71562 | [
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<p>Last year, we did a survey that asked people a question about their belief in climate change. The respondents could select 1 from a list of 5 categorical responses.</p>
<p>In the fall, there was an event that we believe might affect respondents' climate change beliefs, so we're repeating the survey this year. I hav... | g39950 | [
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<p>I have Vectors which have a certain position (Voxels) in an image. I would like to perform a pca to cluster out all Voxels which are correlating with each other.</p>
<p>I have for example three Voxels in 1D:</p>
<pre><code>syn_data_1 = [1;0;0;1;1];
syn_data_2 = [1;0;0;1;1];
syn_data_3 = [0;0;1;0;1];
syn_data = [sy... | g71563 | [
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0.03375968337059021,
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<p><strong>How do I add a neat polygon around a group of points on a scatterplot?</strong> I am using ggplot2 but am disappointed with the results of <code>geom_polygon</code>.</p>
<p>The dataset is <a href="http://pastebin.com/emD71JT5">over there</a>, as a tab-delimited text file. The graph below shows two measures ... | g49834 | [
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<p>I'm thinking of this from a very basic, minimal requirements perspective. What are the key theories an industry (not academic) statistician should know, understand and utilize on a regular basis? </p>
<p>A big one that comes to mind is <a href="http://en.wikipedia.org/wiki/Law_of_large_numbers">Law of large numbers... | g71564 | [
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<p>I'm trying to find more information on how to measure and detect increases in activity in twitter list activity. I have access to all the tweets produced by a list of users. The idea is to try to predict or detect when there is some breaking news that everyone is talking about.</p>
<p>A sensible thing is to plot nu... | g11458 | [
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<p>I'm trying to utilize economic and industry data to forecast sales of industrial companies. I have numerous economic and industry indices and as a first step I would like to indentify those indices that are good leading indicator for sales. I have already utilized graphing, but I was hoping there was a statistic tha... | g71565 | [
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<p>I have a k-means clustering result with 35 clusters, there are 5000 documents that each belong to one of the 35 cluster. I would like to visualize the results of the clustering algorithm on a scatter plot (or something similar) where each document is colored based on which cluster they belong to, and their distance ... | g44043 | [
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<p>This question is intentionally written in a very abstract way, because I am interested in a generic solution, or for pointers to different possible concrete cases in different fields:</p>
<p>I am measuring a particular quantity in a sample of subjects taken from a given population, and I want to apply a null hypoth... | g28768 | [
0.004995016381144524,
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<p>$A$ and $B$ play a dice game where a player wins if their score is higher. $B$ wins if their score is equal. What is the probability of $A$ winning if both the players roll their dice $n$ times and choose their best scores (out of their $n$ throws)?</p> | g71566 | [
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<p>I am taking random numbers from an uniform distribution. After I have taken some number of samples, I plot the probability density function. Now, I'm wondering how should I call the plot. Is it probability density function of uniform sampling distribution? Due to small number of samples it does not look like exactly... | g33102 | [
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<p>Imagine that I have 40 observations in region A, and 50 observations in region B. The total size of region A in square kilometers is 50km, and the total size of region B is 40km. Within each region, each observation has a count of events that ranges from 0 (fairly frequent) to 20.</p>
<p>What is the best way to hyp... | g71567 | [
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<p>I'm new here. I am planning a neuroscience experiment. I will be measuring brain signals from about twenty subjects. I will present the subjects four different kinds of stimuli. After all the data processing, I will have four power spectrums for each participant (one per stimulus type). That is, I will see the magni... | g71568 | [
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0... |
<p>I would like to analyze the email I receive in my Gmail inbox in order to systematically come up with effective Gmail filters for the most common types of email.</p>
<p>I am prepared to manually curate and classify a very large volume of emails (perhaps several 1000) to supply training data, if a machine learning s... | g33104 | [
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<p>I performed multivariate logistic regression with the dependent variable <code>Y</code> being death at a nursing home within a certain period of entry and got the following results (note if the variables starts in <code>A</code> it is a continuous value while those starting in <code>B</code> are categorical):</p>
<... | g71569 | [
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<p>I have been calculating tf-idf for removing stop words in my file. I am experiencing problems. First let us have a look at code I have written..</p>
<pre><code>%MATLAB CODE%
a = load('myexcelfile');
wcf = cell2mat(a.raw(2:end-2,2:7)); % obtaining frequencies in matrix form
</code></pre>
<p>%raw is a cell... | g71570 | [
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... |
<p>There are plenty of resources on how to compute $\beta$-mixing coefficients for a time series and to check if a time series is $\beta$-mixing or not. However, I am struggling to actually find concrete examples of time series I can generate on my own that are defined to be $\beta$-mixing or not. </p>
<p>It would be ... | g71571 | [
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0.04... |
<p>How can one objectively (read "algorithmically") select an appropriate model for doing a simple linear least-squares regression with two variables?</p>
<p>For example, say the data seem to show a quadratic trend, and a parabola is generated which fits the data quite well. How do we justify making this the regressio... | g71572 | [
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<p>I am trying to find the association between BMI and onset age of a condition with linear regression model. I have multiple records of BMI measurement. But the outcome variable, onset age of condition, obviously, only once. </p>
<p>It seems outcome variable should be measured at least twice for a longitudinal study... | g71573 | [
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<p>I have a question about the chow forecast test. I don't understand how you can proof this test. You have: (y_1;y_2)=(X_1 0; X_2 I_(n2))(B;y)+(e_1;e_2) and H_0 is equal to y=0. The restricted is equal to: (y_1;y_2)=(X_1 0; X_2 I_(n2))(B;0)+(e_1;e_2) and the unrestricted is equal to: (y_1;y_2)=(X_1 0; X_2 I_(n2))(B;y)... | g71574 | [
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... |
<p>I am currently trying to solve a problem that should be very easy, yet I am stumped, and help would be GREATLY appreciated!!</p>
<p><em><strong>The background of the question is this:</em></strong></p>
<p>Q: The number of typing errors in a newspaper can be modeled by a Poisson distribution with some mean $μ$. Eac... | g71575 | [
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<p>I have a dataset with multiple correlated binary variables (0/1). Can anyone point me toward a solution for imputing completely random missing values based on information in the other variables?</p>
<p>Below, I provide some code to create a simplified dataset with just 3 correlated binary variables.</p>
<pre><code... | g33111 | [
0.019143912941217422,
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0.005465867463499308,
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0.02658458612859249,
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-0.01214709784835577,
0.008502526208758354,
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0.06204... |
<p>I am looking for a way to graph a triple optimization used in boosting. I did individual cross-validation on shrinkage, number of trees, and interaction depth and found the boundaries of interesting values. Now I am trying to figure out "the best boost".</p>
<p>My dataset contains 1515 rows, 1010 are training and 5... | g71576 | [
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0.024715565145015717,
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<p>I am going to present generalized linear models (GLM) to a small group of people. I like to talk about the contributors of such remarkable work; however, it is hard to find a picture of Robert Wedderburn, perhaps because he passed away too early. Can anyone let me know where to find a picture of him, please? Thank y... | g71577 | [
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<p>In today's pattern recognition class my professor talked about PCA, eigenvectors & eigenvalues. </p>
<p>I got the mathematics of it. If I'm asked to find eigenvalues etc. I'll do it correctly like a machine. But I didn't <strong>understand</strong> it. I didn't get the purpose of it. I didn't get the feel of it... | g49447 | [
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0.004389909096062183,
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... |
<p>I am using <code>svyglm</code> and <code>svyttest</code> to weight my outcome with propensity scores as per: </p>
<p>Ridgeway & colleagues (2013) "Toolkit for Weighting and Analysis of Nonequivalent Groups: A tutorial for the twang package"</p>
<p>So after:</p>
<pre><code>glm1 <- svyglm(X ~ Y, design=desig... | g71578 | [
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0.0015600522747263312,
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... |
<p>I am looking at ways to forecast monthly time series data over a larger geographic region. I have time series weather data (e.g., temperature, precipitation) from multiple stations, and the stations are at certain proximity to each other. In the data set, temperature has slightly increasing trend while precipitation... | g40037 | [
0.028621260076761246,
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<p>The <code>survival</code> package in <code>R</code> appears to focus on continuous time survival models. I am interested in estimating a discrete time version of a proportional hazard model, the complementary log-log model. I have a fairly straightforward survival model, with simple right censoring.</p>
<p>I know t... | g71579 | [
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0... |
<p>I am analyzing a dataset with many parameters (say, 50-200) and I am interested in looking at relations between variables (e.g. in terms of 2-variable scatter plots or 2d histograms). However, for this number of parameters it seems unfeasible to draw a 200x200 array of plots (unless I print it and hang on a wall).</... | g33889 | [
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<p>Suppose we have two samples of a variable taken under different conditions: e.g. A1 without medical treatment and A2 after medical treatment. These are not necessarily normally distributed. Suppose A1 ranges from 0 to 10 and A2 ranges -2 to 15. Now how do I test for the significance of these range increases?<br>
Any... | g42999 | [
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<p>I am very new to statistics and econometrics, I am programmer, but still I need to do one task and get familiar with statistics / econometrics more in details. </p>
<p>1) I have some index that consists of some factors. In total I have more than 30 factors.
2) I have the result index value and values of each seper... | g71580 | [
0.02912498451769352,
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0.0... |
<p>I want to do a regression of a continuous dependent variable (y) (say number of crystals formed) using several independent variables (also continuous), each represent the temperature of each of the plates that are encountered in the crystal-making process (this is a made-up scenario to illustrate the problem I'm hav... | g33121 | [
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0.012244464829564095,
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0.026... |
<p>I'm working with a dataset containing the taxonomic compositions of floras all over the world and performed a non-metric multidimensional scaling (NMDS) based on the relative proportions of plant families within each flora.</p>
<p><strong>My question:</strong> Is it mathematically correct to use the (Euclidean) dis... | g71581 | [
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0.05280855670571327,
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<p>I have a Poisson model with varying densities:</p>
<pre><code>set.seed(1)
df = data.frame(density = 1:5, events = rpois(2000, 1:5))
</code></pre>
<p>If I regress on this, I get that the intercept is approximately <code>log(3)</code>, which makes sense because 3 is the mean of 1:5.</p>
<pre><code>glm(events ~ 1, d... | g71582 | [
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0.027126383036375046,
0.03427779674530029,
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<p>I have data of the following form:</p>
<pre><code>Sample MeasureZZ Time Event
S1 M1 t1 e1
....
</code></pre>
<p>I have calculated the influence of ZZ on survival by</p>
<pre><code>coxph(Surv(t1,e1) ~ MeasureZZ)
</code></pre>
<p>I want to compare this result with external data from multiple sou... | g71583 | [
0.004598268307745457,
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0.012823659926652908,
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0.009287170134484768,
0.008507054299116135,
0.029931535944342613,
... |
<p>Suppose we alter side 6 of a die to appear more than 1/6th of the time. We do not know the actual proportion of the time each side of the die will appear because all or some of the other 5 sides do not have the 1/6 proportion too. What do we need to be 99% confidence of each of the 6 sides of this altered die? How d... | g33122 | [
0.017577342689037323,
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<p>Why do we care about the Hyper-plane wT xi + b = -1 and wT xi+ b =1
if we are searching for an optimal hyper-plane wTxi + b =0
Also what is significance of the alpha's in the solution.
could i get more clear ideas of Vapanik constant C used in soft margin SVM.
Is there any applet so that i can view the effect of al... | g71584 | [
0.013304237276315689,
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0.01973588764667511,
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0.089592389... |
<p>Say I compute monte carlo output from input scenarios. Input are discrete time series. I choose time series as an example to make the problem more obvious - this could be also any curve. </p>
<p>Computation for output is performed at each time: $f(input(t)) = output(t)$. On the time line, we can distinguish severa... | g33124 | [
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0.06136880815029144,
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0.022687381133437157,
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0.03769233077764511,
0.05919993668794632,
0.0001... |
<p>Exercise 3.1.3 : Suppose we have a universal set U of n elements, and we
choose two subsets S and T at random, each with m of the n elements. </p>
<p>What is the expected value of the Jaccard similarity of S and T ?</p>
<p>I am reading the book
<a href="http://infolab.stanford.edu/~ullman/mmds/ch3.pdf" rel="nofol... | g33126 | [
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0.006040771491825581,
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0.012243160046637058,
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0.06446030735969543,
0.0... |
<p>I'm conducting a meta-analysis largely on mean differences data, however I have several articles that report only an odds ratio, N, p value, and confidence interval, and I need to convert this information to Cohen's d. I am having particular trouble calculating the variance for d and the confidence intervals for d. ... | g71585 | [
0.014131709933280945,
0.0006006195908412337,
-0.025504546239972115,
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0.001083710347302258,
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<p>I have the following question for my homework:</p>
<p>Suppose X~exp($\theta$).</p>
<p>We want to test $H_0: \theta=1 vs. H_a:\theta=2$, based on a sample of size 2 - ${X_1,X_2}.$</p>
<p>a. Obtain the most powerful test (MPT) at a significance level $\alpha=.01$</p>
<p>What I am confused about is how to go about ... | g71586 | [
0.014359734021127224,
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0.04296252131462097,
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0.060926079750061035,
0.04848260059952736,
0.04... |
<p>This is what I have understood about neural networks. </p>
<p>There are $L$ layers from input to output (including both) and the equations as follows.</p>
<p>$a(2) = \theta(1) x$</p>
<p>$a(3) = \theta(2)a(2)$</p>
<p>.</p>
<p>.</p>
<p>.</p>
<p>$y = a(L) = \theta(n-1) a(n-1)$</p>
<p>So, we can write $a(L)$ as ... | g71587 | [
0.030120249837636948,
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0.05076318606734276,
0.07211311906576157,
0.0336224... |
<p>I am designing an experiment with 5 variables. Some of the variables have 2 and others have 3 levels. The method that I am going to use is the Latin Hypercube, but I do not not what the sample size should be for a valid experiment?</p> | g33131 | [
0.007823789492249489,
0.07649125903844833,
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... |
<p>An alien is trying to classify a group of only chickens and penguins into, well, chickens and penguins by analyzing 3 independent boolean features A, B, C.</p>
<p>If the animal (in reality) is a chicken, A holds for the animal 60% of the time, B holds 10% of the time, C holds 80% of the time.</p>
<p>If the animal ... | g71588 | [
-0.012740854173898697,
0.040338654071092606,
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0... |
<p>I am trying to classify a data set with 2 boolean values.</p>
<p>I have two classifiers that may/may not be independent. The first one is 65% accurate, and the second one is 60% accurate. </p>
<p>Can I combine the two somehow to get a better classifier? Or will the second one just weaken my prediction?</p> | g71589 | [
0.012742260470986366,
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-0.000... |
<p>I hope you can help me get some confidence in my confidence interval... I am trying to get the confidence interval for a particular (threshold) point on a predicted curve.</p>
<p>I find the confidence interval (C.I.) looks funny, so I would like to know whether what I am doing is correct... Thank you for any advice... | g71590 | [
0.018907077610492706,
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-... |
<p>I have a problem to choose a method for analysing data from my experiment. I have one within-subjects (all four stimuli presented to every subject four times) and four between-subjects factors and a categorical dependent variable (four possible responses).</p>
<p>Also, I want to ask is it ok to use Chi square to te... | g71591 | [
0.008868376724421978,
0.0007212611963041127,
0.015103030949831009,
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0.006315663456916809,
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0.013696894980967045,
0.006186544429510832,
0... |
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