question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I have been reading <a href="http://www.polyu.edu.hk/mm/effectsizefaqs/effect_size_equations2.html" rel="nofollow">http://www.polyu.edu.hk/mm/effectsizefaqs/effect_size_equations2.html</a> and the only difference I can find between the two is that they have ever so slightly different pooled standard deviation values... | g49814 | [
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0.017009766772389412,
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0.011797238141298294,
0.03131325542926788,
0.07200779765844345,
... |
<p>I have production data for several wells. I know that a subset has been treated with a product, and I'd like to determine if the difference in production is due to the product treatment, or the placement of the wells.</p>
<p>For each test well I've collected the $K$ nearest neighbors required to obtain $N$ control ... | g68804 | [
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0.01114... |
<p>I'm using hierarchical logistic regression and having some difficulty.
Im trying to predict self-harm vs none based on IVs age, gender, alcohol, educational attainment. They are all yes/no except educational attainment (e.g. low, mid, high).
I have added age, gender, educational attainment in step 1, and alcohol in ... | g68805 | [
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0.02632327750325203,
0.00... |
<p>I do not know how to use filter to simulate AR and MA models. To me it looks the same way for both MA and AR <a href="http://www.mathworks.com/help/signal/ref/aryule.html" rel="nofollow">Estimate AR</a> so then how do I know that the model is AR or MA ? For example, </p>
<p><strong>Problem1:</strong> For the MA(4) ... | g68806 | [
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0.11968262493610382,
0.04083... |
<p>Given a random variable $X=x_i$ for $i=1,...,n$, with true distribution $p(x)$ and approximate distribution $q(x)$, its cross entropy is given by</p>
<p>$$H(p,q) = -\sum_{i=1}^np(x_i)\log q(x_i).$$</p>
<p>However in practice we find that the true distribution $p(x)$ is rarely if ever known, and thus instead we com... | g29000 | [
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<p>I understand what is RBM. I also accept that in binary RBM, states of RBM are binary. Is that also means the input datasets should be binary?</p> | g68807 | [
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<p>If my state space is $E=1,2,3,4,5,6,7$ and transition matrix is:<br>
\begin{pmatrix}
.5 &0 &0 &.5 &0 &0 &0 \\
0 &.2 &.3 &.1 &.4 &0 &0 \\
.4 &0 &0 &.6 &0 &0 &0 \\
0 &0 &.2 &.8 &0 &0 &0 \\
0 ... | g68808 | [
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<p>$X\sim B(40, 0.3), \bar X$ is the sample mean, and $n$ is number of observations. </p>
<p>I need help in finding $P(\bar X\ge13)$ for a sample of $49$. I have tried the following, please guide.</p>
<p>$\mu=40 \times 0.3=12,$ and $\sigma =\sqrt{40\times0.3\times0.7}=2.8982$ by standardizing I got
$P(Z>\dfrac{1... | g68809 | [
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<p>I'm currently working with accelerated time failure models. However, when I fit a model using <code>survreg</code> in R, the <code>predict</code> function only seems to return expected lifetime. </p>
<p>I'm wondering how one can use a fitted accelerated time failure model to predict probability of survival within a... | g29007 | [
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... |
<p>If I have a data set with daily, weekly and annually seasonality, how often should I update my forecasting model? As I have heard, forecasting models out there can have a good prediction for up to a day ahead for these types of data, hence should I update my model daily to find new values for seasonality for the upc... | g68810 | [
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<p>I want to test whether a correlation coefficient is greater than 0.5.</p>
<ul>
<li><p>What should the null and alternative hypothesis be?</p></li>
<li><p>Should I do a two tailed test or one tailed test?</p></li>
</ul>
<p>Thanks</p> | g68811 | [
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<p>I have a question that's been bothering me research wise. The situation is as follows:</p>
<blockquote>
<p>We are measuring a quantity in
subjects for which we assume that it
differs significantly between
subjects, which we would like to
prove. For each subject we have 2
measurements of this quantity at... | g68812 | [
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<p><br/>
This is somewhat related to <a href="http://stats.stackexchange.com/questions/8192/hypothesis-test-for-whether-correlation-coefficient-is-greater-than-specified-val">another question</a> that I asked. The question I have is, when doing hypothesis testing, when the alternative hypothesis is a range, the null hy... | g68813 | [
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<p>I have 5 variables for 1000 observations. Given the data, I need to</p>
<ol>
<li><p>Calculate probability of hitting top 5 pct in each of the distributions separately. For example, for the value of 123.45 I need to calculate how probable is that this vale is from the top 5pct.</p></li>
<li><p>Calculate probability ... | g68814 | [
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... |
<p><strong>Background:</strong> I am studying the customer satisfaction scores from a random sampling of customers at a technology firm. I have a collection of 13 data points which consist of averages of customer satisfactions scores per year over a course of 13 years. Below is a snap shot of the years, yearly satisfac... | g68815 | [
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<p>I have linear regression code written in R and I have to do the same thing in Java. I used <a href="http://commons.apache.org/math/apidocs/overview-summary.html" rel="nofollow">Apache Commons math</a> library for this. I used the same data in R code and in Java code, but I got different intercept value. I could not ... | g42937 | [
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<p>I am trying to test the effect of each single predictor as well as their combination in predicting an outcome, and I am confusing how to explain these p values:</p>
<pre><code>set.seed(123)
Y<-rnorm(100,10,3)
X1<-rbinom(100,1,0.5)
X2<-Y+runif(100,1,50)
X3<-rbinom(100,50,0.3)
fit<-glm(Y~X1+X2+X3)
#p.v... | g68816 | [
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0.04058089479804039,
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<p>I am working with a database with missing data. I have done "Roderick J. A. Little’s chi-square statistic" and knew that my data are not MCAR. However, I know don't have can I determine if there are MAR or NMAR. I was wondering if there is a test that you may suggest me. Also, how we can know that how many imputatio... | g68817 | [
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<p>Bivariate and multivariate distribution relationship. </p>
<p>If we have say 3 variables where any two variables follow a normal bivariate distribution, then does it necessarily follow a multivariate normal distribution?</p> | g49459 | [
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<p>I am trying to analyze a quite large (~25,000 rows) dataset of cash flow forecasts. Receipts and expenses are aggregated, thus I may end up with the following data:</p>
<p><code>Forecast = 6.0e+04</code><br>
<code>Actual = -5.0e+04</code></p>
<p>But also with<br>
<code>Forecast = 1.0e+06</code><br>
<code>Actual = ... | g10246 | [
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<p>I am doing a systematic literature review on theories for measuring user satisfaction. I have to rate the quality of these theories, and one of the criteria should be the number of participants in the initial validation. So, we assume that each published theory was tested at least once for the initial publication (n... | g68818 | [
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<p>Recently I have come across usage of cluster plot, which combines k-mean clustering along with PCA. The plot shows different clusters plotted using first two PCs. I have checked some of the threads (<a href="http://stats.stackexchange.com/questions/31083/how-to-produce-a-pretty-plot-of-the-results-of-k-means-cluster... | g68819 | [
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<p>We have a random number generator which is supposed to generate 64 bit floats, uniformly.</p>
<p>We want to test whether it is a good uniformly random.</p>
<p>I am not asking the general way to test it, as it was asked here <a href="http://stackoverflow.com/questions/22916519/test-the-randomness-of-a-black-box-tha... | g68820 | [
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<blockquote>
<p>A school is asked to send a delegation of six pupils selected from six badminton players, six tennis players and five squash players. No pupil plays more than one game. The delegation is to consist of at least one, and not more than three, players drawn from each game. Find the number of ways in which... | g68821 | [
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<p>Suppose that the random variable $X_T$ is $O_p(1)$ as $T \rightarrow \infty$. Does this imply that the random variable $\max\{0,X_T \}$ is $O_p(1)$?</p> | g29022 | [
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<p>I need to check if two price lists move togheter. I three methods:</p>
<ol>
<li>Pearson</li>
<li>Spearman</li>
<li>Kendall</li>
</ol>
<p>Could someone explain me why I should use a method instead of other to check if those price lists move in the same direction? I know that Pearson is often used for this kind of a... | g68822 | [
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<p>It frequently comes up in social science that variables that <em>should</em> be distributed in some way, say normally, end up having a discontinuity in their distribution around certain points.</p>
<p>For instance, if there are specific cutoffs such as "passing/failing" and if these measures are subject to distorti... | g29024 | [
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<p>I am using <a href="http://en.wikipedia.org/wiki/K-means_clustering" rel="nofollow">k-means clustering</a> to analyze and obtain patterns in traffic data. This well-known algorithm performs 2 steps per iteration.</p>
<ol>
<li>Assign each object to a cluster closest to it, based on the euclidean distance between the... | g68823 | [
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... |
<p>I am trying to visualize a large multi-dimensional dataset. Each dimension has a different range. Values in one column may range between 0-100 while values in another could range from a few hundred thousand to a few hundred million. Therefore it is really hard to show a graph with a reasonable scale. I would like to... | g39048 | [
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<p>Consider a huge dataset of which the following is a characteristic sample:</p>
<pre><code>stock.id date analyst1 analyst2 analyst3 return
1 Jan 2 -2 1 10
2 Feb -1 2 0 -10
3 Mar 0 2 0 3
4 Apr 0 0 ... | g29039 | [
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<p>Is a distribution free statistic necessarily a nonparametric statistic? Is there a distribution-free statistic that is not nonparametric?</p>
<p>Is a nonparametric statistic necessarily a distribution free statistic? Is there a nonparametric statistic that is not distribution-free?</p>
<p>Are distribution free sta... | g68824 | [
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0.011948580853641033,
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<p>Although I'm fairly new to box plots, I thought I had got the hang of them, until I came upon this one today. I don't know what to make of that bottom "whisker" drawn inside the box.</p>
<p><img src="http://i.stack.imgur.com/2JQ3O.png" alt="enter image description here"></p>
<p>This population is composed by only ... | g68825 | [
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<p>For a function $$ y =f(x), x=\left(x_1, x_2, ..., x_N\right)$$ the law of propagation of uncertainty, see <a href="http://www.bipm.org/en/publications/guides/gum.html" rel="nofollow">GUM sect 5</a>$^{[1]}$ (pdf), is generally given as $$ u_y^2 = \sum_{i=1}^N \left(\frac{\partial f}{\partial x_i}\right)^2 u_{x_i}^2 $... | g68826 | [
0.004138201475143433,
0.004296358674764633,
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0.005266277119517326,
0.039691101759672165,
-0.0... |
<p>I've noticed in many places that it is common do describe experiments in DOE and orthogonality as a geometric figure, why is that?</p>
<p>Also is it connected to orthogonality?</p> | g68827 | [
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0.038820426911115646,
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0.082584448158741,
0.04286... |
<p>I am in great need of help in order to infer the statistical hypothesis tests performed in an old paper. However I need to make some reasonable guesses only from the abstract of the paper since the original text is in chinese which i can not understand (after extensive search i was also unable to find the original t... | g68828 | [
0.05540696159005165,
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0.0... |
<p>I'm considering a mixed-effects model to try to understand factors that influence the number of ticks sampled on wild rodents. My data is nested so that I have one tick count per rodent, multiple rodents per site and multiple sites per year (sites are repeated across years but not every site is present in all years... | g29028 | [
0.02374184876680374,
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<p>I have the following data:</p>
<pre><code>1000 users were invited
990 emails delivered successfully
200 visited the system
60 tried to create an account
58 tried to create an account with a valid email
50 successfully created an account (i.e. chose a secure password)
40 participated by voting
10 posted... | g68829 | [
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0.0009539504535496235,
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0.019708838313817978,
0.07078935205936432,
0.034... |
<p>For some Y variable, that is divided into 3 groups (X), I wish to compare the groups and for the hypothesis that the 90% quantile is the same between all three groups. What tests can I use?</p>
<p>One option I can think of is using quantile regression, are there other alternatives/approuches?</p>
<p>I imagine tha... | g68830 | [
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0.... |
<p>Is there a difference between the phrases "testing of hypothesis" and "test of significance" or are they the same?</p>
<p>After a detailed answer from @Micheal Lew, I have one confusion that nowadays hypothesis (e.g., t-test to test mean) are example of either "significance testing" or "hypothesis testing"?
Or it i... | g49564 | [
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<p>I am currently reading about the standard error. I know about central limit theorem, but I don't understand why, if my variable is normally distributed in the population, the sampling distribution (the distribution of the sample means) is also a normal distribution, no matter of sample size etc.</p> | g68831 | [
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<p>I am getting very different results from glmer (using version 0.999375.37 of lme4) when running in different environments (I can't pinpoint the source of discrepancy, but let's assume some floating point precision difference in the input data). Here is the invocation:</p>
<pre><code>glmer(data=data, n ~ 1 + offset(... | g68832 | [
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0.04806431010365486,
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0... |
<p>I have a distribution like this:</p>
<p><img src="http://i.stack.imgur.com/wHaux.jpg" alt="enter image description here"></p>
<ul>
<li><p>What is name of this distribution?</p></li>
<li><p>As you know we have <code>68–95–99.7</code> rule in <code>normal distribution</code>. Can we have something like this in this ... | g17755 | [
0.03546873852610588,
0.06367476284503937,
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0.0073071736842393875,
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0.03039943240582943,
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0.030168425291776657,
0.02115950547158718,
0.053608451038599014,
-0.01761... |
<p>Here is the kind of data I have:</p>
<p>I have two predictor variables: </p>
<p>1) discrete non-ordinal --> c('a','b','c') </p>
<p>2) discrete ordinal --> c(10,100,200,500)</p>
<p>Response variable: Proportion of TRUE over a list of TRUE/FALSE. If the list is of length 3, my variable can take only 4 values. But ... | g29041 | [
0.032640084624290466,
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0.02277924120426178,
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0.05536624416708946,
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-0.026393216103315353,
0.020421329885721207,
-0.0038520176894962788,
0.03944876417517662,
0... |
<p>Is it possible to compute the function <code>mcp2atm</code> with unequal sample size? I ran the robust Mixed Design ANOVA by using <code>tsplit</code> and want to do post hoc tests now.</p> | g68833 | [
0.011774467304348946,
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0.024493949487805367,
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... |
<p>I don't have any background in math, but I understand how the simple Perceptron works and I think I grasp the concept of a hyperplane (I imagine it geometrically as a plane in 3D space which seperates two point clouds, just as a line separates two point clouds in 2D space).</p>
<p>But I don't understand how one pla... | g68834 | [
-0.006353934295475483,
0.03912486135959625,
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0.030949505046010017,
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0.0608516633510589... |
<p>I use MCMC (Metropolis-Hastings) to sample posterior distributions of three parameters using a nonlinear least-squares objective function to calculate the likelihood of a parameter sets.</p>
<p>I want posteriors for about 500 different conditions, each time I calculate a posterior with MCMC. </p>
<p>Since it is ha... | g68835 | [
0.06848924607038498,
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0.0029655396938323975,
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0.012593709863722324,
0.0040766592137515545,
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0.016229839995503426,
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0.06453638523817062,
-0.0056210970506072044,
0... |
<p>We're forecasting sales data for one of our clients on a weekly basis. Sales is forecasted for each organizational unit.</p>
<p>The sales data is forecasted via different algorithms and/or algorithm parameters.</p>
<p>So, for every organizational unit, about 10 different forecasts are generated. Now I want to find... | g68836 | [
0.045175548642873764,
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0.042279958724975586,
0.034324780106544495,
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0.02178317867219448,
0.0660279244184494,
0.012555441819131374,
0.06497187912464142,
-0.035... |
<p>I am doing an audit looking at survival for a particular cancer. I have done a univariate analyses and Kaplan-Meier curves using Prism Graphpad looking at prognostic factors which may affect survival. I now want to enter the significant factors into a multivariate analysis.</p>
<p>I shall be using SPSS version 21.<... | g68837 | [
-0.019138187170028687,
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-0.0016379925655201077,
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0.008774496614933014,
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0.00207866495475173,
0.03340801224112511,
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0.033728525042533875,
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0.... |
<p>I'm having a set of data's, say </p>
<pre><code>Question,
Question's Main Category,Main Category followers,
Question's Related Categories,Each Related Categories followers,
Whether it got answer in 24hrs [Yes/No]
</code></pre>
<p>Now, I need to analyse a database with thousands of sets of data's like given above ... | g68838 | [
0.036132313311100006,
0.04339234158396721,
-0.006821236107498407,
0.0032246303744614124,
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0.07453352212905884,
0.0034372014924883842,
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-0.02539670281112194,
0.005248940084129572,
-0.013995405286550522,
0.03678375482559204,
0.... |
<p>Suppose that I've a data with a total of 30,000 observations. Each observation has a total of 6 values, 3 per condition. I'm interested in, let's say, testing if the means of these two conditions for each of these observations are different or not. For this, we typically apply a statistical test of choice to each of... | g29043 | [
0.016714241355657578,
0.006343183107674122,
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0.02147505059838295,
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0.03347492963075638,
0.02111409418284893,
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-0.006273297592997551,
0.020226985216140747,
-0.022388437762856483,
0.04389125481247902,
0.053... |
<p>My task is to evaluate the effectiveness of an intervention. In my study, there are one control group and one intervention group. There are two time points, baseline and endpoint.
And I use the score of some questionnaire as outcome measures. </p>
<p>My strategy to show/test the effectiveness is to compare the chan... | g856 | [
0.03039867989718914,
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0.0181674063205719,
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0.04888417571783066,
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0.026235193014144897,
0.03608652576804161,
0.025212517008185387,
-0.019130079075694084,
0.01081... |
<p>My data set consists of a large number of time series of two frequencies: daily and monthly. I am interested in doing a predictive regression on a monthly and weekly basis.</p>
<p>I am thinking of dividing my data set in two (daily and monthly), and then do principal component analysis on each subset individually a... | g68839 | [
0.0229924488812685,
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0.03136182203888893,
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0.05646253377199173,
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-0.04730691760778427,
0.09065128117799759,
0.0004642418643925339,
-0.011340395547449589,
0.011... |
<p>What technique would you use to understand the statical significance of a test where the target outcome is a continuous measure?</p>
<p>Say there are three tests</p>
<p>Control, A and B each with 50k samples and they generate the following revenues of 1054, 750 and 450.</p>
<p>I've done this with discrete measure... | g29026 | [
0.025410644710063934,
0.0007354958797805011,
0.013154113665223122,
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0.033441923558712006,
0.03346196934580803,
0.006087592802941799,
-0.045190587639808655,
0.012370923534035683,
-0.06334884464740753,
0.031831905245780945,
... |
<p>If you flip a fair coin indefinitely, how likely is it that, at some point, you will have evidence that the coin is not fair?</p>
<p>What I mean is this: Take a fair coin and select a $p$-value. If we were to flip the coin $100$ times, there would be some threshold proportion $Q$ such that if the propotion of heads... | g29044 | [
0.03526252135634422,
0.05315224081277847,
0.002109286841005087,
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0.016376402229070663,
0.05816293880343437,
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-0.016507763415575027,
0.0021850524935871363,
0.03212783858180046,
0.006225235294550657,
-0... |
<p>Assume a collection of independent exponential random variables $y_{1}, \ldots, y_{n}$ with means $\mu_{1}, \ldots, \mu_{n}$; where $\mu_{i} = \beta_{0}+\beta_{1}x_{i}$.</p>
<p>How can I find the profile likelihood of $\beta_{1}$?</p>
<p>From what I gather, the profile likelihood is a technique for eliminating so-... | g68840 | [
-0.010602432303130627,
-0.04650639370083809,
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0.004280519671738148,
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0.0432157889008522,
0.014998084865510464,
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0.03146860748529434,
-0.09183566272258759,
0.01946769282221794,
0.01592441461980343,
0.0417... |
<p>I want to create a model matrix for a quadratic regression in R. I have a matrix $X$, where each column is a covariate. Currently, I'm using the code:</p>
<pre><code>Model = model.matrix(~ 1 + X[,1] + X[,2] + X[,3] + I(X[,1]^2/2) +
I(X[,2]^2/2) + I(X[,3]^2/2) + I(X[,1]*X[,2]) + I(X[,1]*X[,3])+I(X[,2]*X[,3]))
</co... | g29046 | [
-0.0009474767721258104,
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-0.01774340495467186,
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0.048072729259729385,
-0.03594888746738434,
0.06688351929187775,
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0.005801032762974501,
-0.023182621225714684,
-0.014344047755002975,
0.012850937433540821,
... |
<p>I'm keeping some fish for toxicity test and will analyze specific parameter after exposing toxicants. I am keeping the fish in normal condition and check the parameter daily as "baseline". I plan to run unit root test to confirm whether there is change after toxicant exposure. However, I'm not quite sure how long th... | g68841 | [
0.027492593973875046,
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0.006605746690183878,
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0.009557370096445084,
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0.0483354888856411,
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0.02452835999429226,
0.0021021817810833454,
0.11404763162136078,
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-0.00... |
<p>I am analyzing some group-randomized longitudinal trial data with three time points using mixed effects model. Some people missed 1-2 time points, and I didn't exclude any cases with missing dependent variable prior to running the analysis. When I was asked by a colleague to report the predicted value, I hit into a ... | g29047 | [
0.03563343361020088,
-0.052107494324445724,
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-0.010097797028720379,
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0.036970432847738266,
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-0.015711350366473198,
0.013610046356916428,
-0.0070375725626945496,
-0.0036978204734623... |
<p>The following is the output for a mixed model example. The only difference between fm1 and fm2 is the random factor "URBAN", why the df for fm2 is 5 but not 4? Any help would be great.</p>
<pre><code>> anova(fm.null, fm1, fm2)
Data: example
Models:
fm.null: SCIENCE ~ 1 + (1 | GROUP)
fm1: SCIENCE ~ URBAN + (1 | G... | g68842 | [
-0.046603698283433914,
-0.048912640661001205,
0.007756202947348356,
-0.05311250686645508,
0.04817074537277222,
-0.015330522321164608,
0.047864023596048355,
-0.0012002651346847415,
-0.05091635137796402,
-0.06524200737476349,
-0.035169851034879684,
0.008032013662159443,
0.03076145611703396,
... |
<p>This may be a trivial question, but as a research psychologist I do not have a robust statistics background to answer it.</p>
<p>It appears to me that the likelihood function--$L(\theta | \text{data}) = P(\text{data} | \theta)$--is committing the <a href="http://en.wikipedia.org/wiki/Confusion_of_the_inverse" rel="... | g23519 | [
0.07222174108028412,
-0.01799015887081623,
0.017119472846388817,
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0.004299949388951063,
0.020254015922546387,
0.020750707015395164,
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-0.0532291904091835,
0.016178319230675697,
0.003482841420918703,
0.015237892977893353,
-0.0... |
<p>My research study is in development economics. My data consist of more than one independent variables (continuous and categorical) as well as more than one dependent variables (categorical 5-point Likert scale). I want to find out their relationships, therefore regression (ordinal logistic) is the best choice.</p>
... | g68843 | [
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0.023381967097520828,
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-0.01601463370025158,
0.011834325268864632,
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0.03683626279234886,
... |
<p>In the comments to the answer to <a href="http://stats.stackexchange.com/questions/41628/imputation-of-missing-response-variables">my question</a> I stated <em>"Many rows have only 1 missing variable, so to exclude the row think leads to bias (they are not MCAR)"</em> and in reply I was told <em>"You're wrong, see R... | g39087 | [
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<p>I've a large number of curves over a finite interval. Given a new curve C, I want to find a set of curves in the database s.t the area between a matched curve and C is less than a certain threshold.</p>
<p>Is this a standard problem? If so, what is it called? What algorithm can I use to solve this (besides the triv... | g68844 | [
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<p>Say we have 5 items, and people are asked which item they like. Multiple answers are possible, but also no answer is possible. The people are categorized according to factors like gender, age, and so on. One possible approach to analyze the differences between genders, age groups and so on is making use of the <a hr... | g37659 | [
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<p>For $z=W^\mathbf{\intercal}(x-m)$ where $k$ columns of $W$ are the top $k$ principal components of a given dataset $x$ and $m$ is the mean, how can I prove that $z$ is diagonal?</p>
<p>$x$ is the original dataset (dxN dimensional matrix) and $m$ is the mean of $x$(1xN dimensional matrix) and $k$ is a number less th... | g68845 | [
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<p>Let's say I have a "kidney catheter" data set. I'm trying to model a survival curve using a Cox model. If I consider a Cox model: $$h(t,Z) = h_0 exp(b'Z),$$ I need the estimate of the baseline hazard. By using the built-in <code>survival</code> package R function <code>basehaz()</code>, I can easily do it like this:... | g68846 | [
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<p>I'm curious as to how putting noninformative priors on the regression coefficients in a GLM compares to maximum likelihood estimation, <em>in frequentist terms</em>. A dispersion parameter $\phi$ is of course a source of trickiness, so perhaps we assume that these are estimated using empirical Bayes. </p>
<p>In the... | g68847 | [
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<p>While going through a statistics course for medicine students, I ran accross a problem related to incidence rates. The context of the problem is a chapter about the Poisson distribution. In the problem, 2300 smokers are followed over a 1 year span during which 24 of them develop lung cancer. They then want to comput... | g44536 | [
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<p>I have the log-likelihood function:</p>
<p>$$l(p_i,y_i) = \sum_{i = 1}^n \left( \ln(p_i) + y_i \ln(1 - p_i) \right) $$</p>
<p>And I need to calculate the maximum likelihood estimator of $p_i$. When I do this, for some reason when differentiating, the summation sign vanishes. Why is this?</p>
<p>EDIT: To calculat... | g29056 | [
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<p>I've got two different sets of data. Each set of data is a two dimensional matrix, filled with real values. What I want to do is measure how well these sets of data correlate (so that a perfect fit would have a value of zero). For example, if the two sets of data, when plotted, are each very far apart from each othe... | g68848 | [
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<p>Is there any way to edit a scatterplot created in SPSS/PASW after exporting/copying and pasting it into a Word document.</p>
<p>I am finding that when I copy and paste my graph from SPSS/PASW into Word, the font size decreases. </p>
<p>I can enlarge the graph in Word by dragging the corners but this makes the font... | g68849 | [
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<p>This may sound very basic, but I have this problem:
I've got a queue of data with a window size of 300. New data is added at one end, old values are removed from the other end.</p>
<p>I expect the queue data to stay more or less consistent, e.g.: 10,12,15,10,20, then start to rise sharply: 15,10,20,22,25,26,28,30,3... | g29059 | [
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<p>I've never done something like this before, thus I do not even know where to start with calculating whatever I need.</p>
<p>Following scenario:</p>
<p>We measure a medical value (Glucose) with our device, and also measure a laboratory reference value to compare our value to.</p>
<p>Now for a paper I was asked to ... | g68850 | [
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<p>Is there a convenient way in R to calculate a <a href="http://www.amstat.org/publications/jse/secure/v8n3/preston.cfm#Section2" rel="nofollow">probability prediction interval</a>
for a count sampled from Poisson($\lambda$), for known lambda? That is, for a given
$\alpha$, find $a$ and $b$ such that $P(a\le X\le b)\g... | g68851 | [
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<p>In the literature, is there any asymmetric $S$-shaped function that maps the interval $[0, 1]$ to interval $[0, 1]$?</p>
<p>Unfortunately I can't post figure so I just describe what I mean in text. The function I want should be monotonic increasing. In the meanwhile, for a real number $c < 0.5$, the function</p>... | g68852 | [
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<p>I have a data set consisting of one continuous response variable and about 70 predictors. Using this data, I want to construct a linear regression model. However, I don't know what predictors are worth including in the model, so I'll need to utilize a variable selection method that will allow me to isolate specific ... | g68853 | [
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0.02191... |
<p>Consider the following R code:</p>
<pre><code>example <- function(n) {
X <- 1:n
Y <- rep(1,n)
return(lm(Y~X))
}
#(2.13.0, i386-pc-mingw32)
summary(example(7)) #R^2 = .1963
summary(example(62)) #R^2 = .4529
summary(example(4540)) #R^2 = .7832
summary(example(104))) #R^2 = 0
#I did a search ... | g29063 | [
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0.057... |
<p>So my data consists of a distance matrix for some points, and a table classifying the points as either red or green. I want to know if there is any difference between the red and green points. I did UPGMA clustering and they don't look different (doesn't seem to be any tendency for red or green to cluster together) ... | g39099 | [
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0.008... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/3438/calculating-percentile-of-normal-distribution">Calculating percentile of normal distribution</a> </p>
</blockquote>
<p>Edit: I think the hint is Box-Muller transformation. Any ideas?</p>
<p>I am try... | g49815 | [
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0.003968904726207256,
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0.07237055897712708,
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... |
<p>I am dealing with the topic of seasonal variation and stroke. I would like to do time series analysis.For time variable I have stroke onset month and all the other variables are categorical in nature. How should I analyze these data?</p> | g68854 | [
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<p>I am trying to find out which SVR is suited for what kind of data. I found out 4 types of SVRs: epsilon, nu, least squares and linear. I understand linear SVR is more or less like lasso with L1 Reg. But what is the difference between the remaining 3 techniques? </p> | g68855 | [
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<p>My problem should probably be built up from the beginning, so lets start there. I performed a certain experiment 25 times. Every time, the experiment consists of 5000 measurements, and each measurement returns either 1 ('yes') or 0 ('no'). I know that each time I measure 1, the probability that this measurement is c... | g29068 | [
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<p>I understand that in a decision perspective, identifiability of a model is needed to ensure the convergence (with increasing number of observations) of the parameters to estimate through a single value. But, if the non-identifiability of a given model is not a modeling artifacts but clearly characterises some "inacc... | g68856 | [
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0.029180796816945076,
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0... |
<p>I am doing a regression analysis using dummy variables, but I need to include weights. I am using data from an opinion poll, and I am trying to make sure that the sample is regionally representative. So I would like to apply weights for responses from certain regions. How do I do this with dummy variables? Can I sim... | g68857 | [
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... |
<p>From <a href="http://www.itl.nist.gov/div898/handbook/prc/section4/prc433.htm" rel="nofollow">nist</a> for the test statistic in one-way ANOVA:</p>
<blockquote>
<p>The mean squares are formed by dividing the sum of squares by the
associated degrees of freedom.</p>
<p>Let $N = \sum_i n_i$. Then, the degrees... | g68858 | [
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0.010016210377216339,
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0.... |
<p>I have a list of items and various parameters for each items. For each item on my list i need to identify items which are similar to the item from my whole population . I am planning on using K-NN algorithm for the same. However, however i am not sure how to pick up the relevant parameters. Can anyone guide me on wh... | g29071 | [
0.009212673641741276,
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0.01767783798277378,
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0.047419559210538864,
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<p>I'm making a project connected with identifying the dynamics of sales. My database concerns 26 weeks (so equally in 26 time-series observations) after launching the product, 126 time-series=126 different products.</p>
<p>I used clustering to group products with similar dynamics of sales. I applied two different app... | g29072 | [
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<p>I'm running a mixed model on some data. I want to calculate confidence intervals for my model. </p>
<p>For this I have adapted the following code section from <a href="http://glmm.wikidot.com/faq" rel="nofollow">Predictions and/or confidence (or prediction) intervals on predictions (lme4)</a>. The problem is that I... | g68859 | [
0.02178923413157463,
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<p>Is there a statistical test to check the difference between groups (for example a paired sample proportion test), but where some of the observations of the two groups are dependent and some of the observations are independent? </p>
<p><strong>For example:</strong></p>
<p><strong>Context</strong>: The observations... | g68860 | [
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<p>This is an elementary question, but I wasn't able to find the answer. I have two measurements: n1 events in time t1 and n2 events in time t2, both produced (say) by Poisson processes with possibly-different lambda values.</p>
<p>This is actually from a news article, which essentially claims that since $n_1/t_1\neq... | g68861 | [
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<p>Is the Yates' correction for continuity used only for 2X2 matrices? </p> | g68862 | [
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<p>A webinar the other day by an a/b testing company had their resident "Data Scientist" explain that you should validate your results by re-running the experiment. The premise was, if you select 95% confidence, there is 5% (1/20) chance of a false positive. If you re-run your experiment with the same constraints, now ... | g29077 | [
0.0033818655647337437,
-0.015914713963866234,
0.005311119835823774,
0.0261743925511837,
0.020942550152540207,
-0.03087393008172512,
0.047917429357767105,
-0.01782025583088398,
0.022304439917206764,
0.0055585093796253204,
0.009255665354430676,
0.08139967918395996,
0.0008282563649117947,
-0.... |
<p>I have the total number of calls received each week and have plotted them on a chart, going back nearly 3 years.</p>
<p>By eye it seems that there was a massive drop over Christmas, that doesn't seem to have recovered, it seems that there has been a step change in requests.</p>
<p>Is there a test I can do that can... | g68863 | [
-0.010768752545118332,
0.024632982909679413,
-0.025241630151867867,
-0.05759943649172783,
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0.07102100551128387,
-0.02942422591149807,
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0.009111969731748104,
0.057798728346824646,
0... |
<p>I am doing factor analysis to check the factorial validity of a 14-items scale with four subscales. Two items have low (less than 0.3) correlations with other items in the subscale to which they belong. However, they load considerably (greater than 0.32) on the factor (latent variable) to which they correspond. Unde... | g68864 | [
0.03406849876046181,
0.020292367786169052,
0.004161740653216839,
-0.06829958409070969,
0.051698822528123856,
0.018703632056713104,
0.019738992676138878,
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-0.022010089829564095,
-0.008356685750186443,
-0.017824064940214157,
-0.031376633793115616,
... |
<p>I keep seeing this term crop up in financial math papers but am unable to find a definition/explanation without purchasing whole articles! Can someone shed some light?</p> | g29078 | [
0.09992896765470505,
0.07430069893598557,
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-0.03906642273068428,
-0.05932912603020668,
0.00729279313236475,
0.03027699887752533,
-0.03... |
<p>I've completed PCA analysis, in R with VEGAN package, of some ecological data on tree health. There are 80 trees total (so, 80 'sites') divided into four treatment categories. I've got the data plotted with color coded points--colors according to the treatment groups. Rather than plotting individual sites/trees on P... | g68865 | [
-0.01691408082842827,
-0.03130112588405609,
-0.005402689334005117,
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-0.06180930137634277,
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-0.026299970224499702,
0.081635020673275,
0.007100679911673069,
0.07471391558647156,
-0.019... |
<p>After doing some research on the topic, I have noticed a surprising deficit of inference packages and libraries that rely on message-passing or optimization methods for Python and R. </p>
<p>To the best of my knowledge, these methods are extremely useful. For example, for a Bayes Network (directed, acyclic) belief-... | g68866 | [
0.02885241061449051,
-0.03219524025917053,
0.014225051738321781,
0.0027979151345789433,
0.02164616994559765,
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0.027433056384325027,
0.01084427535533905,
-0.042192213237285614,
-0.05777643993496895,
0.01763761416077614,
-0.055507756769657135,
0.050846826285123825,
0.085... |
<p>What does this mean?</p>
<blockquote>
<p>Asset prices follow a mixture of normal distributions with a mixing process dependent on the unobservable information arrival process.</p>
</blockquote> | g68867 | [
0.0495978407561779,
0.03470109775662422,
-0.017909850925207138,
-0.036840084940195084,
0.027535218745470047,
0.04349607601761818,
0.032602496445178986,
0.022776255384087563,
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-0.01292220689356327,
-0.02632858231663704,
0.01538301631808281,
0.035597722977399826,
0.0017... |
<p>I'm performing some basic analysis on a large data set (n-size after restrictions about 4,000) to supplement some qualitative historical research. The goal is to produce a variety of confidence intervals for proportions, and I've run the analysis in Stata using both the <code>ci</code> command (with <code>aweights</... | g68868 | [
0.017102040350437164,
0.004969357512891293,
-0.02461105026304722,
-0.05395248532295227,
0.02200455591082573,
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0.03905937448143959,
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-0.05955852195620537,
0.03557712584733963,
0.010282227769494057,
0.04024801403284073,
0.0165... |
<p>I have a group of observations, 25, And I want to perform a 25-fold cross-validation (leave-one-out).</p>
<p>Here is my code,</p>
<pre><code>library(MASS)
min.m <- lm(formula= Mass ~ 1, data=mean.mydata)
fsel.m <- step(min.m, direction = "both", scope=sel.fmla, steps = 5)
fsel.fmla <- as.formula(object=f... | g68869 | [
0.004834981169551611,
0.01931900717318058,
-0.016937801614403725,
-0.08940146118402481,
0.009321746416389942,
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0.0892537385225296,
0.028231849893927574,
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-0.04149463027715683,
-0.01915416680276394,
0.00421470170840621,
0.03521798551082611,
0.037546... |
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