question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I am having some confusion relating to cross-validated deviance of a lasso fit. I am not sure what is being done. </p>
<p>Let's say I run lassoglm in Matlab for my dataset having 1000 examples and 15 features with a CV of let's say 100. What does it do?</p>
<p>And what does the plot lassoPlot with CV do? </p>
<p>... | 74,237 |
<p>If I construct a 2-D matrix composed entirely of random data, I would expect the PCA and SVD components to essentially explain nothing.</p>
<p>Instead, it seems like the the first SVD column appears to explain 75% of the data. How can this possibly be? What am I doing wrong?</p>
<p>Here is the plot:</p>
<p><img s... | 74,238 |
<p>I am confused about "parametric" and "non-parametric":
Our topic is nonparametric estimators for probability of default. So first of all, we consider the generalized linear models, as an example we have probit and logit:</p>
<p>$\pi (x)=G(\beta_0 +\sum \beta_i x_i)$</p>
<p>These generalized linear models are para... | 74,239 |
<p>I want to understand how I can compute the eigenvectors and the eigenvalues of a matrix using dimensional reduction.I have a Matrix $M$ of dimensions $n$ x $d$ using dimension reduction I can compute the eigenvectors and the eigenvalues of the Covariance matrix $MM^t$. After computing these eigenvectors and eigenval... | 46,056 |
<p>I have a preliminary study with very small sample size (n=26), and I want to test for differences between males and females and similar things, so I have to divide the sample and make comparisons of 13 vs 13 subjects.</p>
<p>Is there a test I can use to give an idea of what the differences might be? Is it possible ... | 74,240 |
<p>I'm trying to compute ANOVA effect sizes from papers that provide an F value without other information. If I understand correctly, the effect size for a single-factor ANOVA is
$$
\eta {2} = \frac{ss_{between}}{ss_{between} + ss_{error}}
$$</p>
<p>And the F value is:
$$
F = \frac{(N-k)ss_{between}}{(k-1)(ss_{betwee... | 74,241 |
<p>I am classifying different texts and I wondering about some features that are highly correlated. I have 49 features. Some features are absolute counters (integers) but most features are relative counters(float between 0-1).
I am running F-score (univariate) and I am getting the following three features with the high... | 36,997 |
<p>I have a data set of a bag of words. I randomly choose some points and use them for testing and the others are used for training.</p>
<ul>
<li>case (1) I just take each data-point from the test set and classify it as
having the same class label as its nearest point from the train set.</li>
<li>case (2) I do the cla... | 36,998 |
<p>I have a continuous random variable $X$ (positive). I want to simulate its distribution with a discrete distribution and calculate $E[X]$ from that discrete distribution. So, the obvious approach is to divide the range of the random variable into step size of $h$; let the CDF values at the points $0,h,2h,\ldots,Nh$ ... | 40,272 |
<p>I got an example calculation for multiplicative model, which is shown as follows:</p>
<pre><code>Quarter 1 2 3 4
Average 0.866 1.0005 1.403 0.660
--------------------------------------------------
Adjustment 0.0176 0.0176 0.0176 0.0176
Seasonal factor 0.884... | 74,242 |
<p>I have zero inflated response variable I am trying to predict. I am facing few issues applying different regression models that should correct for this.</p>
<p>This is my 10,000 obs dataframe</p>
<pre><code> e_weight left_size right_size time_diff
Min. :0.000 Min. : 1.000 ... | 74,243 |
<p>Is there a way I can model a discrete time random walk with random variance? The stochastic vol models I have found all seem to be continuous and assume vol is normal.</p> | 74,244 |
<p>I am looking at setting up some website load testing scripts and need some help in finding a formula to estimate how many concurrent users are browsing a website at peak times, based on common metrics such as visits, average page views per visit, and average visit duration.</p>
<p>For example:</p>
<p>Peak visitors... | 37,001 |
<p>I'm using <code>heatmap.2</code> to cluster my data, using the centroid method for clustering and the maximum method for calculating the distance matrix:</p>
<pre><code>library("gplots")
library("RColorBrewer")
test <- matrix(c(0.96, 0.07, 0.97, 0.98,
0.50, 0.28, 0.29, 0.77... | 74,245 |
<p>When finding the maximum margin separator in the primal form we have the quadratic program</p>
<p>$$min\frac{1}{2}||\theta||^2$$
$$\text{ subject to: } y^{(t)}(\theta \cdot x^{(t)} + \theta_0) \geq 1, \ t=1,...,n,$$</p>
<p>saying basically to find the maximum margin separator. The margin size will be:</p>
<p>$$\f... | 74,246 |
<p>This is not a question about implementation:</p>
<p>I have a GLMER model with a significant three way interaction. Neither of the two way interactions or main effects are significant. I accept this model and leave all lower order effects in the model, but want to plot this three way interaction: x, y, and then z ... | 74,247 |
<p>Is it possible to fit a data curve to another data curve?</p>
<p>Please see this plot</p>
<p><img src="http://i.stack.imgur.com/2iHKM.jpg" alt="enter image description here"></p>
<p>I do not have the model for the black data curve or I don't want to model it. But I want to see how the red data curve fits/matches ... | 74,248 |
<p>The final theorem in Chapter 19 of Meyn and Tweedie's <a href="http://probability.ca/MT/" rel="nofollow">Markov Chains and Stochastic Stability</a> tells us that if the mean inter-arrival time $\lambda$ of a GI/G/1 queue is greater than its mean service time $\mu$, then the queue is positive Harris recurrent.</p>
<... | 37,006 |
<p>I have done an AMOVA analysis on mtDNA sequences, partitioned on 14 populations (with a variable number of individuals in each populations), and I insert all the population in the same group.</p>
<p>From the AMOVA analysis I have obtained significant value for Fst among populations, but when i try to compute pairwi... | 34,791 |
<p>I have a situation where we are detecting anomalies based on data implied from the table data. </p>
<p>As an example, I have data on registered individuals spending time on the portal. Based on this, I have some logic driven by the interval between successive login-ins/ activity on portal. We have used arbitrary du... | 74,249 |
<blockquote>
<p><img src="http://i.stack.imgur.com/BX2wm.jpg" alt="enter image description here"></p>
</blockquote>
<p><strong>My attempt at making sense of the problem:</strong><br>
The problem provides us with the sum of squares (SS; I believe that's the $18.1$). We can use the SS along with the number of samples ... | 74,250 |
<p>To check if unilateral pairs (defined below*) are coordinated (i.e. move together) in a flock of N coordinated individuals, we generate hypothetical (null) distribution of a certain focal parameter of our system (the frequency that 2 individuals are nearest neighbors along a track). The null model is simulated by sh... | 37,011 |
<p>I have been using JAGS but I am not quite sure how it actually simulates it values. I need to know in a general sense what's going on in the background. </p>
<p>Thanks for the help</p> | 37,013 |
<p>This is my attempt to find the discrepancy in the matching process for <code>R</code> package <code>"Matching"</code> and user written function <code>"psmatch2"</code> in <code>Stata</code><a href="http://stats.stackexchange.com/questions/52889/matching-results-completely-different-in-r-and-stata"> [Details]</a>. </... | 74,251 |
<p>A student's t distributed rv $X$ has characteristic function but no moment generating function. I wonder if cf(X)=$E[e^{itX}]$, why we cannot take $t=-iu$ to get the mgf $E[e^{uX}]$? (This question may be very silly...)</p>
<p>If we cannot know mgf of $X$, is there some accurate numerical way to evaluate $E[e^{X}]$... | 37,015 |
<p>From <a href="http://en.wikipedia.org/wiki/Completeness_%28statistics%29" rel="nofollow">Wikipedia</a>:</p>
<blockquote>
<p>The statistic $s$ is said to be complete for the distribution of $X$ if for every measurable function $g$ (which must be independent of parameter $θ$) the following implication holds:
$$
... | 74,252 |
<p>I have a R data frame like this:</p>
<pre><code>structure(list(Mash_pear = c(0.328239947270445, 0.752207607551684,
0.812118104861163, 0.640824971449627, 0.615568052052443, 0.546635339103089,
0.557460706464288, 0.650480192893698, 0.418044504894929, 0.52962586938499
), tRap_pear = c(0.0350096175177328, 0.2342555077... | 74,253 |
<p>My project is about purchasing power parity (PPP). I am checking whether the real exchange rate of Canadian dollar(CAD)/US dollar(USD), Japanese Yen(JPY)/USD and Great Britain Pound(GBP)/USD has a unit root with Augmented Dickey Fuller (ADF). </p>
<ul>
<li>H0 is - there is a unit root for the series and real ex. r... | 37,018 |
<p>Statistical semi-novice question:</p>
<p>Just following up <a href="http://stats.stackexchange.com/questions/53432/can-ancova-disagree-with-multiple-regression">this question</a>, the fact that the three types of ANOVA exist with an unbalanced design, and that (presumably) you don't necessarily know a priori which ... | 37,019 |
<p>I devised a distance function similar to this form</p>
<p>$d(x,y) = \sum_{i = 1}^{n-1} b(x_i, y_i,x_{i+1}, y_{i+1}) $ </p>
<p>with</p>
<p>$b(x_i, y_i,x_{i+1}, y_{i+1}) = 0 \mbox{ if } x_i \leq 0 \vee y_i \leq 0 \vee x_{i+1} \leq 0 \vee y_{i+1} \leq 0$<br>
$b(x_i, y_i,x_{i+1}, y_{i+1}) = \alpha \cdot \frac{x_{i+... | 74,254 |
<p>I hope that this question does not get marked "as too general" and hope a discussion gets started that benefits all.</p>
<p>In statistics, we spend a lot of time learning large sample theories. We are deeply interested in assessing asymptotic properties of our estimators including whether they are asymptotically un... | 37,021 |
<p>Does anyone know of a good compendium or catalog of compound distributions, or finite mixture representations of those distributions? </p>
<p>I am trying to find out to what extent the common multi-parameter distributions and their generalized forms can be built up from single parameter distributions through compou... | 38,773 |
<p>I came across a study in which patients, who were all over 50, were pseudo-randomized by birth year. If birth year were an even number, usual care, if an odd number, intervention.</p>
<p>It's easier to implement, it's harder to subvert (it's easy to check what treatment a patient should have received), it's easy to... | 74,255 |
<p>The question states: </p>
<blockquote>
<p>Consider a set of random variables $X_i$, where $i=1,...n$. Each $X_i$ is
normally distributed with mean $0$ and variance $1$, i.e. $X_i$ are $\mathcal N(0,1)$.
What is the mean and the variance of the random variable $Y$, where
$Y=X_1+...+X_n$.</p>
</blockquote>
<... | 37,023 |
<p>This is a pretty basic question, but I can't find an answer by searching for different statements of the same problem.</p>
<p>Is there a straightforward way to test if a regression parameter is different from a non-zero value in (non-) linear regression? I can only think of one way, but it seems too roundabout. Her... | 44,244 |
<p>I've done an experiment where I recorded a positive or negative result from a cell.
My data is set in tables of counts of events and trials, but I don't know how to do statistical analysis on binary data, I need to test the significance between the groups I tested.
Can I convert to percentage and do a stats test on... | 37,024 |
<p>So the question states that I'm trying something with an 85% chance of success, if I don't succeed I try again until I do. What is the mean and variance of the number of tries necessary until I succeed?</p>
<p>Thanks!</p> | 46,169 |
<p>As a programmer, I am used to a vibrant documentation system with exhaustive references and tutorials online. Does such a system exist for Stata? Where do people go for quick stata questions (besides Cross Validated)? How did people here learn Stata?</p> | 48,738 |
<p>This may be a very simple question, but I am not sure about my logic.</p>
<p>I have a standard point hypothesis testing scenario, where I collect a sequence of $n$ independent observations $\{x_1,\ldots,x_n\}$ and attempt to classify them as either generated from the distribution $P(x_1,\ldots,x_n;\theta=\theta_0)$... | 74,256 |
<p>I have the survival dataset of a population with a special disease. I´d like to compare this population with the general population to see whether this population has a decreased life-expectancy overall. What I had in mind was to create a control for each patient in the dataset and enter the age, sex and cohort spec... | 74,257 |
<p>I have a set of 40 subjects that performed a task while the variables of interest were being recorded at regular time intervals (0, 1, 2,.... 10 seconds). The task was performed twice, once with and once without the aid of computer feedback. </p>
<p>For most of the variables, the distribution across subjects at eac... | 74,258 |
<p>Using the Stata <code>graph twoway</code> command, I have created a scatterplot with a quadratic best fit line, using the <code>qfit</code> command. How can I get the equation of the best fit line? </p>
<p>Example: </p>
<pre><code>graph tw (scatter y x) (qfit y x)
</code></pre> | 992 |
<p>Proportion, ratio, and percentage data is very common in ecology (eg, % of flowers pollinated, male:female sex ratio, % mortality in response to a treatment, % of leaf eaten by an herbivore). An article was recently published by some applied statisticians in the journal <em>Ecology</em> titled "<a href="http://www.... | 74,259 |
<p>I am trying to use a function from the <a href="http://cran.r-project.org/web/packages/forecast/index.html" rel="nofollow">forecast</a> package, <code>seasonaldummy()</code>, which requires a time series object as input, but I have an <a href="http://cran.r-project.org/web/packages/xts/index.html" rel="nofollow">xts... | 74,260 |
<p>I have several data sets of frequency values (See Fig. 1 for an example).</p>
<p>I'm interested in those tighter clusters (marked by green rectangles) and am using hierarchical clustering in MATLAB (with unweighted average distance method) to separate them. (*)</p>
<p>The spread of these clusters increases with fr... | 37,040 |
<p>I'm having trouble showing that the 2nd central moment is finite. I have $X_1,\ldots,X_n \overset{iid}{\sim} f(x)$ with $E[X_1]=\mu$ and $E[X_1^k]$ exists and is finite for any integer $k \geq 1$. </p>
<p>I would like to use Law of Large Numbers, so I need to show that either $E[|X_1|]$ is finite or that $E[(X_1-\m... | 40,091 |
<p>I have a regression in which I try to understand how much variance of the metric dependent variable each of the regressors explains. I use the package R <a href="http://cran.r-project.org/web/packages/relaimpo/index.html" rel="nofollow">relaimpo</a> (Grömping, 2006) for that purpose, that allocates $R^2$ shares to e... | 37,046 |
<p>It is known that odds ratios enjoy a certain symmetry. For example, the odds ratio of outcome $Y$ is the inverse of the odds ratio of outcome $\neg Y$. Risk ratios, on the other hand, do not enjoy this symmetry. However, risk ratios have the property of collapsibility. So adjusting for a covariate that is not a con... | 74,261 |
<p>Having recently run an experiment, I have been left with a dataset that I don't quite know how best to handle, I think simply due to the number of independent variables to consider.</p>
<h2>Setup</h2>
<p>I have implemented 4 new approaches to solve a problem, which I wish to compare to an existing approach and to ... | 37,049 |
<p>Suppose I have a python function using scipy that returns the expectation $E\left[ X \right]$ for some data assuming it is gamma distributed:</p>
<pre><code>def expectation(data):
shape,loc,scale=scipy.stats.gamma.fit(data)
expected_value = shape * scale
return expected_value
</code></pre>
<p>(My under... | 74,262 |
<p>I'd like to test the hypothesis that there is a monotonic relationship between two variables, without assuming a specific model. What is the most robust (i.e. lowest probability of type-II error) way to do this?</p>
<p>I can think of a few options:</p>
<ul>
<li><p>use a linear model of untransformed data. It'll be... | 48,761 |
<p>I'm trying to measure the impact that rainfall causes in the number of incoming calls in a insurance-company. I have 4 years of daily data.</p>
<p>The plots below shown the correlation plot for each year:
<img src="http://i.stack.imgur.com/KTdSX.png" alt="enter image description here"></p>
<p>The same plots as abo... | 37,051 |
<p>I'm having difficulty understanding one or two aspects of the cluster package. I'm following the example from <a href="http://www.statmethods.net/advstats/cluster.html">Quick-R</a> closely, but don't understand one or two aspects of the analysis. I've included the code that I am using for this particular example.</p... | 37,052 |
<p><strong>Framework.</strong> Fix $\alpha\in ]0,1[$. Imagine you have $n$ $\alpha$-quantile forecast methodologies that give you, at time $t$ for look ahead time $t+h$, an estimation of the quantile of wind power. Formally, for $i=1,\dots,n$, you know how to produce $\hat{q}_{t+h|t}^{(i)}$ at time $t$ for look ahead t... | 37,053 |
<p>I have an odd problem which can be phrased in a general way, and a more specific way. I'm curious about the answers to both. Although, really, it's the k=0 case that I'm really interested in - deriving the answer with respect to some properties of the distribution of m.</p>
<p>These may be totally basic, so, apol... | 74,263 |
<p>As I have written in my question "<a href="http://stats.stackexchange.com/questions/7209/how-much-undersampling-should-be-done">How much undersampling should be done?</a>", I want to predict defaults, where a default is per se really unlikely (average ~ 0.3 percent). My models are not affected by the unequal distrib... | 48,763 |
<p>My data consists of three groups (A,B,C -independent of each other) and each group consists of 1000 correlation coefficients (generated using a stochastic simulation with 1000 iterations, correlating X and Y of the respective groups in each iteration). </p>
<p>Case 1: I would like to test each group whether signifi... | 74,264 |
<p>First off, I'm not trying to crowd source a personal printing press (i.e., not doing this: "I'm using strategies $x$, $y$, $z$ in the stock market and..."). Instead, I'm looking for feedback on research design. </p>
<p>The situation: Many equity/currency/futures traders use technical analysis as part of their trad... | 48,773 |
<p>I've been looking at mixed effects modelling using the lme4 package in R. I'm primarily using the <code>lmer</code> command so I'll pose my question through code that uses that syntax. I suppose a general easy question might be, is it OK to compare any two models constructed in <code>lmer</code> using likelihood r... | 74,265 |
<p>How would I interpret a transformed dependent variable (4th root) with some of its predictor variables transformed as well? In our study, we transformed our dependent variable to 4th root, $Y^\frac{1}{4}$, and one of our predictor variables to $\ln(X)$. How would I interpret that?</p> | 49,681 |
<p>When calculating Adjusted $R^2$ the formula is $1-(1-R^2)\frac{n-1}{n-k-1}$ with $k$ being how many predictors you have. If I am using a model with a single variable but that variable has been put to the 4th, 3rd, and 2nd power like the following, </p>
<p>$\hat{Y}=-0.0162x^4+0.2239x^3-1.0941x^2+2.0972x-0.9513$<... | 37,064 |
<p>If s1 is the variance of a small sample, and s2 is the variance of a larger sample from the same population. Is s1 an unbiased estimator for s2?</p>
<p>I am thinking since a sample variance is an unbiased estimator of the population variance, then s1 and s2 are both unbiased estimators for sigma^2, so s1 and s2 sho... | 37,065 |
<p>I am experimenting with neural network package in R nnet and i have some questions.</p>
<ol>
<li>The regulatory environment i am working on requires me to reproduce my results to show them to the auditors. How can i reproduce my model results after few months/years ? Can i use a seed value to control the model outp... | 37,067 |
<p>In "Elements of Bayesian Statistics" (1990), Florens, Mouchart and Rolin describe two basic forms of reduction of a Bayesian experiment: Marginalization and Conditioning (Ch. 1). I don't understand the conditioning reduction. More precisely, i struggle with the definition of a <em>regular</em> conditional experiment... | 74,266 |
<p>I'm interested in testing a sequence of numbers for randomness. I've done some searching and come across <a href="http://www.stat.fsu.edu/pub/diehard/" rel="nofollow">die hard</a> and <a href="http://www.phy.duke.edu/~rgb/General/dieharder.php" rel="nofollow">die harder</a>. However these tests seem to require some ... | 74,267 |
<p>I am trying to generate confidence intervals for estimates of numbers of fish observed with a very small number of surveys. Most of the numbers of fish observed are very small as well.
The estimate is based upon the ratio of the number of adult fish and redds (fish nests) observed during the observation season.</p>... | 74,268 |
<p>Could you please shed some lights about how to interpret linear regresssion results (2-stage vs. 1 stage)?</p>
<p>For example, I have the following:</p>
<pre><code>lmStage1 <- lm(y~x1)
lmStage2 <- lm(residuals(lmStage1)~x2)
summary(lmStage2)
</code></pre>
<p>vs.</p>
<pre><code>lmAll <- lm(y~x1+x2)
summa... | 74,269 |
<p>I am trying to make predictions using a random forest model in R.</p>
<p>However I get errors since some factors have different values in the test set than in the training set. For example, a factor <code>Cat_2</code> has values <code>34, 68, 76</code>, etc., in the test set that do not appear in the training set. ... | 74,270 |
<p>Let's say there's one DV (<code>Y</code>) and three IVs (<code>X1</code>, <code>X2</code>, <code>X3</code>), and among IVs, <code>X1</code> is a dummy variable.
In the regression model without interaction terms, the results can be represented like this:</p>
<pre><code>Y ~ X1 + X2 + X3
X1 : non-significant
X2 : sig... | 49,515 |
<p>I'm very new to SAS, so please keep that in mind with any responses.</p>
<p>I've been running the following code in SAS:</p>
<pre><code>FILENAME fishfile URL
"http://www.amstat.org/publications/jse/datasets/fishcatch.dat";
PROC FORMAT;
VALUE sexfmt 0="female" 1="male";
VALUE speciesfmt 1="common bream" 2="whi... | 37,079 |
<p>When I perform a linear regression in some software packages (for example Mathematica), I get p-values associated with the individual parameters in the model. For, instance the results of a linear regression that produces a result $ax+b$ will have a p-value associated with $a$ and one with $b$.</p>
<ol>
<li><p>Wha... | 48,796 |
<p>I have a data set with multiple y values per x value. Using Excel the scatter plot and the regression line tools, I wish to apply regression on the data to determine if there is any connection between the data points.</p>
<p>If I just pick the regression trend line (Layout 3) in Excel, it gives me a line with an R²... | 74,271 |
<p>How to estimate probability density function when we have set of feature vectors, but we don't know their statistical distribution?</p> | 74,272 |
<p>I have done many 1-sample T-tests before, but I can't figure out if I am able to use one in this situation. In our experiment, we took 12 individual insects and placed them in a chamber where they could choose to be on whatever side they pleased (One side had sugar in it and the other did not). We recorded the numbe... | 48,276 |
<p>This question has two parts, as I do not understand whether my problem is theoretical (identification of the parameters) or practical (insufficient R skills).</p>
<ul>
<li>Econometrics</li>
</ul>
<p>Most "probit" style models are identified through a normalization of the standard error to one. In my case, I would ... | 37,083 |
<p>I have a dataset that comprises several instances for different patients, with multiple instances per patient. I need to perform some classification tasks and I was using cross-validation, but this way I may have instances for the same patient in the training and the test folds. I would like to perform "leave one pa... | 74,273 |
<p>This is a homework problem. I have figured out part (a) but I need help with part (b). I include part (a) for completion. </p>
<p>Suppose $X_1,\ldots,X_n$ are iid Poisson random variables. Furthermore, let $Z_n$ be the proportion of zeroes observed i.e. $Z_n = n^{-1}\sum_{i=1}^n 1\{X_j=0\}$. </p>
<p>$(a)$ Find the... | 74,274 |
<p>An <strong>interim analysis</strong> is an analysis of the data at one or more time points prior the official close of the study with the intention of, e.g., possibly terminating the study early.</p>
<p>According to Piantadosi, S. (<a href="http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0471727814.html">Clinical... | 38,207 |
<p>I have some data to analyze where $y$ is dependent of $x$ - a linear regression was used.</p>
<p>It's a question from an exam, so I think it should be solvable. The regression was used to estimate the mean <em>miles per gallon</em> (response) from the <em>amount of miles driven</em> (predictor).</p>
<p>I have the ... | 37,085 |
<p>If I have an arima object like <code>a</code>:</p>
<pre><code>set.seed(100)
x1 <- cumsum(runif(100))
x2 <- c(rnorm(25, 20), rep(0, 75))
x3 <- x1 + x2
dummy = c(rep(1, 25), rep(0, 75))
a <- arima(x3, order=c(0, 1, 0), xreg=dummy)
print(a)
</code></pre>
<p>.</p>
<pre><code>Series: x3
ARIMA(0,1,0) ... | 74,275 |
<p>I want to perform quadrat count analysis on several point processes (or one marked point process), to then apply some dimensionality reduction techniques.</p>
<p>The marks are not identically distributed, i.e. some marks are appearing quite often, and some are pretty rare. Thus, I cannot simply divide my 2D space i... | 37,087 |
<p>I have a small question about a small research that I wanted to do regarding stock symbol similarities and their abnormal returns. I have about a sample of 10 000 stocks and I calculate how much they differ from each other (which gives a matrix of 10K x 10K with their "difference measure").</p>
<p>Now I was plannin... | 37,088 |
<p>According to Wikipedia:</p>
<blockquote>
<p>Although in practice [Fisher's exact test] is employed when sample sizes are small, it is valid for all sample sizes.</p>
</blockquote>
<p>If Fisher's exact test can provide the exact p-values in lieu of the approximation that is given by the chi squared, what is the r... | 49,928 |
<p>I have a set of density plots that contain the distribution of stock prices. Each graph has 5 density plots as follows that shows the distribution of monthly returns based on their ratings - a,b,c,d,e. A is the lowest rank while E is the highest rank. I need to come up with a score that tells me how different/away t... | 74,276 |
<p>This is data cleaning and preparation stage question for me. I apologize if the question is basic, but I am a beginner. I have a dataset of a bit less than 4500 records. This is a survey and <code>year of birth</code> is an important field. Now 670 records do not have this information. I am inclined to think that I ... | 37,090 |
<p>Take this example:</p>
<pre><code>data <-matrix(c(227,751,193,541), ncol=2)
column1 <- c(227, 751)
probabilities <- c( 193/(193+541), 541/(193+541) )
chisq.test(data)
chisq.test(column1, p= probabilities)
</code></pre>
<p>when i apply the chi-squared test providing a matrix the results says that this is ... | 74,277 |
<p>In my project, one of my objectives is to find outliers in aeronautical engine data and chose to use the Replicator Neural Network to do so and read the following report on it (<a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.12.3366&rep=rep1&type=pdf" rel="nofollow">http://citeseerx.ist.psu... | 74,278 |
<p>I have performed an experiment on plants and have some trouble analysing the data. For the experiment, we have three replicates (in time), two species and three treatments. In each experiment, we recorded the height of the plants. The dataset looks like this:</p>
<pre><code> replicate | treatment | species | height... | 74,279 |
<p>Disclaimer: Statistics is not my strong side, so if my question is nonsense I apologize. I'm a beginner, but really wanting to understand this.</p>
<p>My question is: why do I get so widely different parameter estimates when using different transformations on my data in a non-linear regression ?</p>
<p>I'm trying ... | 74,280 |
<p>I wanted to find out if there are any implications to using OLS when i have cardinal data as dependent variables. So my dependent variables are counts of a certain outcome and they exist as natural numbers 0,1,2,3,...N</p>
<p>My independent variable is a series of realized volatility.</p>
<p>Is there a better way... | 74,281 |
<p>I have a background in computer programming and elementary number theory, but no real statistics training, and have recently "discovered" that the amazing world of a whole range of techniques is actually a statistical world. It seems that matrix factorizations, matrix completion, high dimensional tensors, embeddings... | 45,474 |
<p>Given two multivariate gaussian (say in 2D with mean $\mu$ as a 2D point and convariance marix $\Sigma$ as $2$x$2$ Matrix) $N_1(\mu_1,\Sigma_1)$ and $N_2(\mu_2,\Sigma_1)$, I would like to derive the pdf of $N_1+N_2$. </p>
<p>Can any one point me to the reference where i can find the pdf derivation of $N_1 + N_2$.</... | 74,282 |
<p>Good day all,</p>
<p>Suppose that I am conducting a questionnaire study that is trying to measure level of awareness of subjects about a programming language and find the relation of those level of awareness to working conditions and methods etc.</p>
<p>To improve my precision I decided to go with stratified sampl... | 37,106 |
<p>I want add to my regression additional features to complicate my model and lower bias, after searching around internet is seems a good idea is to add square features, that can help regression learn in coefficients more knowledge.</p>
<p>I want add to my regression model square of pairs of features $x * y$, i think ... | 74,283 |
<p>I have a set of variables for building credit scorecards with logistic-regression. I need to bin some variables, for e.g. years of credit history. What is the method to determine how many bins and what is the interval for each bin? Thanks</p> | 74,284 |
<p>So, when I did first year stats in undergrad, we did an experiment where we tampered with a bunch of coins, to see if it would cause a statistical difference in the results. This is a graph of the ratio of $heads:tosses$ for each series of flips:</p>
<p><img src="http://i.stack.imgur.com/0KGkp.png" alt="coin tosses... | 74,285 |
<p>I have a "basic statistics" concept question. As a student I would like to know if I'm thinking about this totally wrong and why, if so: </p>
<p>Let's say I am hypothetically trying to look at the relationship between "anger management issues" and say divorce (yes/no) in a logistic regression and I have the opt... | 74,286 |
<p>I have time series data that represent dates/times of trades taken in a financial market. </p>
<p>I would like to assign a score to this data that represents whether the trades are <code>mostly clustered</code> around particular time values or if they are <code>mostly spread out</code> evenly. I am going to have a... | 37,109 |
<p>I am going to be hosting a number (~10) of <a href="http://en.wikipedia.org/wiki/Potluck" rel="nofollow">potluck meals</a> over the course of the summer, my pool of people to invite is about 40 people with about 10-15 coming to each meal. So I figure this would be a good opportunity to record data over time about th... | 74,287 |
<p>in a plot of my time series there is clearly visible that there is structural break, but I have to find the exact date. I want test this with the chow test. Although I understand how to perform this test if the date of the structural break is know, by simply using a linear regression with two dummy's one for the int... | 74,288 |
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