question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
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<p>I'm a newbie analyst and I'm facing a machine learning / regression problem which I cannot solve. The data I need to use in my analysis consists of information about press subscriptions of some companies. Each company has its unique ID but it further splits into separate company's "employees" with different values o... | g61924 | [
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<p>Now I have a <code>R</code> data frame (training), can anyone tell me how to randomly split this data set to do 10-fold cross validation?</p> | g61925 | [
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<p>I'm looking into an R package 'lokern.'
It provides two bandwidths selectors, global and local plug-in bandwidth.
I would like to understand the difference between two methods.
My understanding is 'global' bandwidth uses one bandwidth for the entire data set, and 'local' bandwidth uses different bandwidths in one da... | g18724 | [
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<p>Suppose I have a training set $\mathcal{T}^N = \{(x_i , y_i) \in \mathbb{R}^{d} \times \{0,1\}\}$, where the data are i.i.d draws from some distribution.
Now I learn a classifier $\hat{h}$ from these data using some deterministic algorithm. WLOG take the Euclidean norms of the $x_i$ and of $\hat{h}$ to be $1$ and de... | g61926 | [
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<p>I have produced a mixed effects model as follows:</p>
<p><code>lmer(TotalPayoff~Type+Game+PgvnD*Asym+(1|Subject)+(1|Pairing),REML=FALSE,data=table)</code> </p>
<p>each pairing contains 2 subjects and each Subject is in 2 different pairings with different subjects. Have I structured the random effects in the corr... | g48672 | [
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<p>I have used quantile regression to estimate a particular coefficient for the 10th, 20th, ... 90th percentiles. Now, I want to estimate the mean effect of the coefficient across the whole distribution. Using ordinary least squares to estimate the mean effect, however, is inappropriate given the heteroscedastic, non... | g61927 | [
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<p>I have a data set of x- and y-values, that I want make a linear fit of. Using <code>polyfit(x,y,1)</code> I get the coefficients <code>a</code> and <code>b</code> for a linear fit <code>ax = b</code> for this data, but I would also like to find the uncertainty or standard deviation for these coefficients. Does anyon... | g37917 | [
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<p>From the echocardiography database at a tertiary care center, 1,625 subjects (mean age, 44 6 14 years; 47% men) with normal echocardiographic findings between 2000 and 2009 were identified. Gender dif- ferences and association with body surface area were assessed retrospectively for right atrial long-axis and short-... | g61928 | [
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<p>I am running a multiple regression of the form y~a+b+c+ab+ac+bc</p>
<p>I have checked the VIF values for the direct effects - should I check them for the interactions? </p>
<p>I am assuming not as that would equate to looking at the multicolinearity between a variable and itself (albeit in an interaction) which w... | g61929 | [
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<p>The dichotomous variable I want to use for a point-biserial correlation has very unequal n's ($n_1=140$, $n_2=6$). Would this be breaking any rules? What would this mean for my results? Would it just limit the statistical power? </p> | g61930 | [
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<p>Assuming a sample of random variables where the error terms for each random variable ($y_{i}$) are given by $\epsilon_{1}, \dots, \epsilon_{n} \sim N(0, \sigma^{2})$, a linear model is developed such that:</p>
<p>$$ y_{i} = \beta_{0} + \epsilon_{i} $$</p>
<p>then, using OLS, finding,</p>
<p>$$ \frac{d}{d\hat{\bet... | g61931 | [
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<p>I am confused between these two terms: <em>sensitivity</em> and <em>concordance</em>. What I understand about these two terms:</p>
<p><strong>Concordance:</strong> the number of pairs where actual 1s have higher predicted probability of becoming 1s than 0s divided by total number of pairs.</p>
<p><strong>Sensitivi... | g18732 | [
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<p>I am working on a piece of software to detect opinions in text. As a simplistic example, I would like my algorithm to tell me that Andrea has a positive opinion <strong><code>+1</code></strong> (rather than neutral <strong><code>0</code></strong> or negative <strong><code>-1</code></strong>) of New York when I enter... | g263 | [
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<p>I would like to do a t-test in R. Unfortunately, statistics has never been my best subject, so I'm wondering what the output of t.test in <code>R</code> exactly mean.<br>
For testing purpose I performed a t-test on two normal distributed vectors with equal parameters. Since both distributions have the same parameter... | g61932 | [
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<p>I am not sure what to do with this regression residuals.</p>
<p><img src="http://i.stack.imgur.com/hXxz4.jpg" alt="Regression Diagnostics"></p>
<p>The Normal Q-Q plot is indicating that residuals are non-normal (not too extreme) and residual variance is not constant (not too bad). My input variables are factor var... | g61933 | [
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<p>I have a predictive model with just OK performance, and I'm trying to improve it with feature engineering. </p>
<p>My question: is it valid to create new features by looking at trends in the training set? For example, I noticed that the metric I am trying to predict tends to be higher during the months of Decembe... | g61934 | [
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<p>Ok, Let me tell you that this is the very first time that I have no idea with the question below. I can not find a solution or anything that will lead me to it. I say this to prevent comments "what did you do?". I apologize in advance.</p>
<p>This is one of the questions in Peter M. Lee's Bayesian Statistics: An In... | g34652 | [
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<p>When using Newey-West standard errors for my t-statistics of the slope coefficients in an OLS regression, can I still use the usual critical values for two-sided tests? (1.645 for 10% significance, 1.96 for 5% and 2.58 for 1%)</p> | g61935 | [
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<p>To make a Computerized Adaptive Test out of a sample of 20 dichotomous items a typical course of action would be to:</p>
<p>1) calibrate respondent data with a R package like mirt or ltm using Rasch, 2PL etc.</p>
<p>2) create an itembank based on obtained item parameters using catR</p>
<p>then, for each item/test... | g61936 | [
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<p>my question is:</p>
<p>What is the difference between the variance of an individual forecast and the
variance of a mean forecast?</p>
<p>I know that the two variances are different, but what consequences hat the forecast on the data that is forecasted?</p> | g18738 | [
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<p>I want to use a distribution to predict the p-value (whether it's just noise) of each element in this dataset.
But I don't know what distribution should I use. Could anyone give me some tips about it?</p>
<p><img src="http://i.stack.imgur.com/96aNg.png" alt="The histogram of the data"></p> | g48680 | [
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<p>I have been seeing a lot of papers on sparse representations lately, and most of them use the $\ell_p$ norm and do some minimization. My question is, what is the $\ell_p$ norm, and the $\ell_{p, q}$ mixed norm? And how are they relevant to regularization?</p>
<p>Thanks</p> | g18742 | [
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<p>I'm having trouble understanding identifiability. Specifically, I'm not sure, in the following example, why $P\left(C\right)$ cannot be identified. Here's the example:</p>
<p>You have 2 unfair coins with the following probabilities:</p>
<p>$$P\left(H|C_1\right)=1/4$$
$$P\left(H|C_2\right)=3/4$$</p>
<p>Each coin h... | g61937 | [
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<p>Suppose we are given various reports on projected sales of Product $X$ for $5$ years starting in $2013$. All of the reports just give the results and not the methodology as to how they arrived at the predictions. Suppose we are interested in the projected sales of Product $X$ for $10$ years. So we already have the p... | g61938 | [
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<p>Thanks to anyone who can help!
I`ve done a survey with Likert-scale questions with about 1,500 participants. Initial analysis in SPSS showed no outliers (using box-plot) but scores were not normally distributed for any of the factors, as assessed by Shapiro-Wilk's test (p < .001). Since the independent variable h... | g22274 | [
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<p>Pretty new to R and to stackexchange. My apologies if I make any faux pas.</p>
<p>I'm working with the North Carolina births data from irss.unc.edu. I have a data frame <code>NCBIRTH1450</code> with several lists, all of which have numeric or NA values. I'm just trying to calculate some proportions from the data... | g18746 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/26041/can-svm-do-stream-learning-one-example-at-a-time">Can SVM do stream learning one example at a time?</a> </p>
</blockquote>
<p>It takes 30 minutes to create SVM model from the whole dataset. The train... | g49629 | [
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<p>I want to generate a bivariate Gaussian dataset. The dataset includes a total of 800 results drawn randomly from four two-dimensional Gaussian classes with means $(-3,0)'$, $(0,0)'$, $(3,0)'$, and $(6,0)'$, all with the same variance-covariance matrix</p>
<p>$$\Sigma = \pmatrix{0.5 & 0.05 \\ 0.0... | g61939 | [
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<p>Consider $n$ <em>fixed</em> subsets of a finite universe $U$: $A,B,C,D,\ldots$</p>
<p>Then let $Coll$ be the collection of sets we get from the closure of the set $\{U,A,B,C,D, \ldots\}$ under the operations $\cup,\cap$ and set-theoretic difference.</p>
<p>(As an aside, to help picture Coll, note that $|Coll|≤ 2^... | g61940 | [
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<p><img src="http://i.stack.imgur.com/AwHU7.png" alt="enter image description here"> I need to chart a number of indicators to evaluate emergency response times for a fire department. In our case, most values should be around 2 minutes, but the range can be between 0 and 10 minutes.
I've been working with bar chart... | g18749 | [
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<p>I'd like to estimate the unique effects for each variable in a linear model,
however I am unsure if I calculating these correctly.</p>
<p>I am using a model estimated using each of the variables in my data plus a
binary interaction with each variable, e.g. <code>y ~ x + x:z</code> where x is a vector and
z is tw... | g18751 | [
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0.005825154948979616,
0.0470714271068573,
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0.006898737978190184,
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0.035662345588207245,
-0.013764413073658943,
0.... |
<p>I have a good feel for the types of data that go with most colormaps. But I don't know what kind of data one would want to use the following types of colormaps:</p>
<p>Flag:</p>
<p><img src="http://i.stack.imgur.com/T3uMo.jpg" alt="Flag in <code>matplotlib</code>"></p>
<p>Prism:</p>
<p><img src="http... | g61941 | [
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<p>I am exposing several experimental organisms to a toxin in the food. If the dosage is high enough, they will die. I am examining the number that are dead after a day. For practical reasons, the dosage they get is not directly under my control. I have decided to model the number that are dead after one day as a bi... | g61942 | [
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... |
<p>1) Is it okay to run a Mann-Whitney U test on unequal sample sizes i.e. two groups (N=11, N=12)or is there an alternative test?
2) What does it mean when one obtains a zero value for a Mann-Whitney U test (bearing in mind I obtained zero values before with equal sample sizes)</p>
<pre><code>Ranks
**S... | g61943 | [
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0.009121338836848736,
0.007989144884049892,
0.0037414375692605972,
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... |
<p>I've calculated income inequality metrics (Gini/Hoover/Theil coefficients) for several populations. I know I can make claims like "this population has a higher Gini coefficient, so its distribution in this variable is more unequal than this other population."</p>
<p>But is it possible to make more quantifiable clai... | g46040 | [
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0.06221596896648407,
... |
<p>Apologies in advance if this question seems trivial -- I am a biologist and have little experience in statistics.</p>
<p>I have six non-normal distributions (they're positively skewed): three are replicates from a drug treatment and three are replicates of an untreated control. I want to determine if the distribut... | g61944 | [
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<p>I have a data set of 100 geographic regions for which the unemployment rate has been observed during the last 9 years. Now, I want to simulate/forecast from this data the next year unemployment rate for all the 100 regions.
What would be a suitable approach? I was thinking to use an auto-regressive mixed effect mod... | g61945 | [
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<p>I ran into a problem (question) with biological data analysis and don't know how to solve it. Will try to explain problem as simple as possible: </p>
<hr>
<p><strong>Dummy example:</strong></p>
<p>There are 10000 textbooks in a library;<br>
There are 1000 physics textbooks (10% of all the books);<br>
I noticed t... | g61946 | [
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<p>I am about to conduct two Principal Component Analyses (PCA) on species abundance data and species composition data. I have about 12 different locations where abundance data for over 50 invertebrate species has been collected. The software I am using has an option to log transform and scale the data prior to analyse... | g48709 | [
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<p>I am newbee and i am trying with functional data analysis. I have a 8x11 matrix data, how can i input into R as an object in this form:</p>
<pre><code>$hgtm
boy01 boy02 boy03 boy04 boy05
1 81.3 76.2 76.8 74.1 74.2
1.25 84.2 80.4 79.8 78.4 76.3
1.5 86.4 83.2 82.6 82.6 78.3
1.75 88.9 85... | g61947 | [
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0.06189526617527008,
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0.04793864116072655,
0.039828963577747345,
-0... |
<p>I plotted below the standarized results of: </p>
<ul>
<li>RAND()</li>
<li>RAND() * RAND() </li>
<li>...</li>
<li>RAND() * RAND() * RAND() * RAND() * RAND() * RAND()</li>
</ul>
<p>It seems that the results are getting to zero, is that because you're multiplying a bunch of numbers close to zero together, or is the... | g46074 | [
0.02805539220571518,
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0.... |
<p>I have a questionnaire that contains some skip questions. Like, say, the 3rd question is a yes/no type question. Only those who answered "yes" to the 3rd question are requested to answer the 4th, 5th and 6th question and those who answered "no" are requested to skip these three questions. </p>
<p>I am sorry that I ... | g61948 | [
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0.... |
<p>I can't seem to find a definitive answer to my question.</p>
<p>My data consists of several plots with measured means varying from 0.27 to 0.57. In my case, all data values are positive, but the measurement itself is based on a ratio of reflectance values that can range from -1 to +1. The plots represent values of ... | g18764 | [
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... |
<p>I am using ridge regression on highly multicollinear data. Using OLS I get large standard errors on the coefficients due to the multicollinearity. I know ridge regression is a way to deal with this problem, but in all the implementations of ridge regression that I've looked at, there are no standard errors reported ... | g48714 | [
-0.01142636127769947,
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0.007433637976646423,
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0.06456504017114639,
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0.008769613690674305,
-0.049693092703819275,
0.02644132450222969,
0.048544298857450485,
0.03... |
<p>I hope this is an appropriate forum to post this question. I recently upgraded my R software from 2.15.0 to 3.0.2. I also upgraded the lme4 package from .999999-0 to 1.1-2. After doing so, the results from one of my linear mixed models analyses have changed a bit unexpectedly. In some respects, I was expecting some ... | g61949 | [
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0.012564106844365597,
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0.016706254333257675,
0.012772390618920326,
0.033591628074645996,
0.02955339476466179,
0.0072... |
<p>I am trying to understand the Particle Filter and the motivation to use it over the regular Sequential Importance Sampling. As far as I understand until now:</p>
<p>1- We try to estimate the expectation of a function $f_n:\mathbb{R}^{n} \mapsto \mathbb{R}$ under the multivariate density $\pi_{n}(x_{1:n})$, namely $... | g61950 | [
-0.02344675175845623,
0.004609561525285244,
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0.028108609840273857,
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0.01986067369580269,
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0.035937342792749405,
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0.06277366727590561,
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0.... |
<p>I have three general questions that I am really struggling to answer:</p>
<p>a) When we have nested data (e.g. employees nested in departments which are nested in companies which are in specific geographical regions) how data mining methods adjust to nesting?</p>
<p>b) Are data mining methods ""immune"" to nested ... | g61951 | [
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0.041524309664964676,
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0.01026... |
<p>In particular, I am referring to the Pearson product-moment correlation coefficient.</p> | g61952 | [
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0.006733546499162912... |
<p>I would like to perform a linear regression. However, the predictor variables are families of variables indexed by time. Let's say the regression problem is:</p>
<p>target ~ x(1)+x(2)+...+x(40)+y(1)+...+y(40)</p>
<p>and imagine the x(t) and y(t) are measurements in 40 successive years. The variables inside the fam... | g61953 | [
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0.06061612814664841,
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0.0... |
<p>The input is a bunch of numbers. How can I calculate a threshold that there are 10% of the totally amount of numbers are above this threshold. I think this is equally as to calculate the distribution function, but what I need is the threshold number, not the </p> | g18767 | [
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0.025264384225010872,
0.03276856243610382,
0... |
<p>I'm going through Yaser Abu-Mostafa's <a href="http://work.caltech.edu/telecourse.html" rel="nofollow">Learning from Data</a> course, and I'm having some trouble getting my head around data contaimination.</p>
<p>So we know stuff like VC-analysis can give us some gaurentee that hypotheses in a set $\mathcal{H}$ wil... | g18768 | [
0.03181324154138565,
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0.027667269110679626,
0.024308983236551285,
0.05303865671157837,
0.00... |
<p>In a data set with thousands of data points, I am testing different short-term and longer term data outputs based on 5 rolling data points all the way to 100 rolling data points (which each value being a separate column in excel: 5, 6,..., 100). </p>
<p>The test I developed (with rudimentary knowledge of the whole ... | g39726 | [
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0.0006593563593924046,
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0.003651998471468687,
0.005989335477352142,
0.08017074316740036,
... |
<p>Suppose my sample comprises 350 instances. Each instance has two independent binary (<code>pos</code> and <code>neg</code>) evaluations, <strong>A</strong> and <strong>B</strong>. If my alternative hypothesis is that A is more often positive than B, how would I express whether the difference is statistically signifi... | g61954 | [
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0.008777514100074768,
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0.004657239653170109,
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0.0033593294210731983,
0.044370200484991074,
-0.009419457986950874,
-0.0004403802449814975,
0.033172301948070526,
0.025833070278167725,
0.004668751731514931,... |
<p>I often need to forecast for future periods in monthly series of data.</p>
<p>Formulas are available to calculate the confidence interval at alpha for the next period in the time series, but this never includes how to treat the second period, and third, etc.</p>
<p>I'd visually imagine that if any forecast was gra... | g34 | [
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0.04465550184249878,
0.053585998713970184,
0.0646464079618454,
-0.03... |
<p>I would like to know what are the various techniques and metrics used to evaluate how accurate/good an algorithm is and how to use a given metric to derive a conclusion about a ML model.</p> | g18773 | [
0.023169653490185738,
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0.011186686344444752,
0.0019616216886788607,
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0.1039898470044136,
0.0... |
<p>It seems that data mining and machine learning became so popular that now almost every CS student knows about classifiers, clustering, statistical NLP ... etc. So it seems that finding data miners is not a hard thing nowadays. </p>
<p>My question is:
What are the skills that a data miner could learn that would mak... | g61955 | [
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0.0061662327498197556,
0.00919303484261036,
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0.038704585283994675,
0.08950480818748474,
-0.... |
<p>I sometimes see that the cost function, along with the regularizer is divided by 1/2m where m is the number of examples. When we are trying to find the minimum of the cost, why does scaling by this amount matter? It doesn't affect where the minimum is. Example:</p>
<p><img src="http://i.stack.imgur.com/V54zN.png" a... | g18775 | [
0.05368199571967125,
0.02712855488061905,
0.0030343951657414436,
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-0.017638223245739937,
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0.005354119930416346,
0.021... |
<p>I am familiar with the concept of cointegration.</p>
<p>But I hear sometimes people talking about colinearity (or collinearity) for time series.
A set of points is collinear if they are on the same line. But what does that mean for time series?</p>
<p>Is it exactly the same as cointegration of order 1?
Or is there... | g61956 | [
0.03068816289305687,
0.01797264628112316,
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0.023740312084555626,
0.016043061390519142,
-0.00... |
<blockquote>
<p>A Lab has been asked to evaluate the claim that drinking water in a
local restaurant has a lead concentration of 6 parts per billion
(ppb). Repeated measurements follow a normal distribution and the
population standard deviation is taken to be 0.25 ppb. α = 0.01. </p>
<p>• A sample of three... | g61957 | [
0.04697725549340248,
0.0359908826649189,
0.00009166936069959775,
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0.015708232298493385,
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0.016685793176293373,
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-0.027978947386145592,
0.024480808526277542,
0.015769943594932556,
-0.04862387850880623,
... |
<p>I'm running a <code>RandomForest</code> in R on a set of data with many variables. Using <code>varImpPlot()</code> I know how important is each variable to explain the target variable. However, I would also like to know whether a <strong><em>variable affects positively or negatively the target value</em></strong>.</... | g34811 | [
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0.00012849224731326103,
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0.030699584633111954,
0.02110814303159... |
<p>I am observing a random variable $X \in \mathbb{R}$ which can be assumed to be normally distributed with mean $\mu$ and variance $\sigma^2$. I am interested in fitting a posterior distribution over the <strong>unknown variance</strong> which, according to wikipedia, can be given in closed form by an inverse-gamma. M... | g18780 | [
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0.014295374043285847,
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0.038137972354888916,
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0.0... |
<p>I did a literature review and ended up with a lot of data in the kind of "10 out of 20 studies found x while 4 out of 8 studies found y".</p>
<p>To be more precise; I looked up the contribution of seafood to environmental impact categories in different studies. Here is a short extraction of my data:</p>
<p><img sr... | g18781 | [
0.02508818730711937,
0.07389675825834274,
-0.011169791221618652,
-0.07739211618900299,
0.006643622647970915,
-0.04842870309948921,
-0.004036338068544865,
0.008734201081097126,
-0.009751205332577229,
-0.01406094804406166,
0.049273937940597534,
-0.012438708916306496,
0.06212900951504707,
0.0... |
<pre><code> id sam1 sam2 sam3 sam4
gene1 33 23 88 98
gene2 0 0 99 95
gene3 77 100 44 65
gene4 0 0 0 0
gene5 100 100 100 100
:
:
gene20000 58 33 78 56
</code></pre>
<p>I have 20K genes (rows) and four samples (col... | g37441 | [
0.054913561791181564,
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0.01772506721317768,
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0.0191... |
<p>An <a href="http://stats.stackexchange.com/questions/30456/geometric-interpretation-of-penalized-linear-regression">older question</a> gives an intuitive explanation of how penalized linear regression works, using two separate contours: one for the least square objective, one for the penalty term (i.e. regularizatio... | g61958 | [
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0.028... |
<p>I came by the post "<a href="http://www.r-bloggers.com/post-hoc-pairwise-comparisons-of-two-way-anova/">Post-hoc Pairwise Comparisons of Two-way ANOVA</a>" (responding to <a href="http://rtutorialseries.blogspot.com/2011/01/r-tutorial-series-two-way-anova-with.html">this post</a>), which shows the following:</p>
<p... | g18785 | [
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0... |
<p>I fit a GLM to a dataset. Now I want to see where the difference between my groups is, so I tried to run a Tukey HSD as a post-hoc test. </p>
<p>Because of it is a GLM, I can't use <code>TukeyHSD()</code>. So I tried to run a Tukey test with: </p>
<pre><code>summary(glht(my.mod, mcp(treatment="Tukey")))
</code><... | g18786 | [
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... |
<p>I want to perform a power analysis for a 2 sample t-test for the difference in means. However, instead of computing the required sample size, I would like to compute the required difference in the means given the sample size.</p>
<p>The sample size is fixed at $n=34$ (i.e. 17 per group). Due to different reasons, i... | g61959 | [
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... |
<p>I want to analyze some data of a questionnaire on presence (I deal with experiments on virtual reality).
The questionnaire was provided twice to particpants performing the experiment, after each of the two provided conditions.
The 6 questions of the questionnaire were evaluated by participants on a 7-points Likert ... | g61960 | [
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... |
<p>Say I have a list of numbers $X = \{x_1, x_2, \dots, x_n\}$, and I expect them to be drawn from a certain distribution. For my case it is the Binomial distribution $P(x) = \binom{n}{x}p^x(1-p)^{n-x}$, but I think I general answer would be the most helpful. What is the standard and most rigorous way I could determine... | g61961 | [
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<p>I measured half maximal effective concentration (EC50) of three different RNA construct and I want to test whether they are statistically significance or not. Which test should I use?</p> | g61962 | [
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0.007188528310507536,
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<p>What are the best quantitative models for trend detection?
I.e. market trend.</p> | g28304 | [
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<p>The quantile regression is defined through the optimization approach. But I am not clear how does the function of $\rho_{\tau}(u)$ related to the $\tau$-th quantile. Or in other words, how to derive the equation of the $\tau$-th sample quantile $=argmin \sum\rho_{\tau}$ </p>
<p><img src="http://i.stack.imgur.com/Du... | g61963 | [
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0.049338992685079575,
... |
<p>I want to test the presence of an interaction term in a logistic regression with glm().</p>
<p>The formula is:</p>
<pre><code>Gest.hypertension ~ ART.conc + Parity + Age + Smoke + Nulliparity + Syst.disease.type
</code></pre>
<p>With Age the only continuous variable and the others categorical. </p>
<p>The intera... | g61964 | [
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0.009597... |
<p>I've read a lot about Cross Validation to estimate prediction error, specifically for selecting the number of components in a PCA model (I'm not doing SVD/PCA, but it's very similar), but I can't find much literature on using CV for really, really large sparse data. Could anyone help me out with paper links, persona... | g61965 | [
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<p>i have data that includes clicks, spend, signups and date. </p>
<p>for 1 week, i turn off advertising spend to see what clicks and signups are.
the next week, i turn advertising back on to see what the new clicks or signups are.</p>
<p>Given this 2 sets of data, how can i run regression analysis to see how impactf... | g61966 | [
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0.02423347719013691,
0.06502780318260193,
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0.021686... |
<p>One of properties of PCA states that the sum of the variances of the principal components is equal to the sum of the variances of the explanatory variables. I wonder how to interpret this as I've always thought that we do not consider $X$'s as random variables. I'm quite new to probability theory and I need to get i... | g18794 | [
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0.019188322126865387,
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0.059... |
<p>Social science PhD student here looking for a little help. </p>
<p>I set out to collect around 300 online surveys for a study, but ended up with over 4,000. At that sample size should I sub-sample my results because it's more likely that significant results will be found because of the sample size?</p>
<p>Thanks. ... | g49627 | [
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0.02562396414577961,
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0.012769938446581364,
-... |
<p>I'm creating an app that logs daily data from my users.
Data includes:</p>
<ul>
<li>waist circumference, weight (Quantitative data) </li>
<li>certain conditions like psoriasis, migraines, fatigue (Qualitative data rated from 1 to 5). </li>
</ul>
<p>Showing charts for each entitiy is fairly easy. </p>
<ul>
<li>How... | g61967 | [
0.0092537309974432,
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0.028549373149871826,
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0.06284511834383011,
0.02701086364686489,
0.11602576076984406,
0.0... |
<p>Suppose I have two independent normal variables $X$ and $Y$ with known mean and variance. Defining $Z = X+Y$, what is the most straightforward way to compute $\mathbb{E}\left[X|Z\right]$?</p>
<p>I am writing
\begin{align}
\mathbb{E}\left[X|Z\right] & = \int_x x f_{X}(x|Z=z) \mathrm{d}x \\
& = \int_x x \fra... | g61968 | [
0.004717056639492512,
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0.014422871172428131,
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0.030383149161934853,
0.08404123783111572,
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... |
<p>I have a dataset containing some approx. 11 million instances, all of which can be labelled as either class A or class B. I know a priori that approx. 1,000 of these instances belong to class A, and the rest are class B. However none of the instances are actually labelled. So, I would like to be able to sample these... | g9973 | [
0.006611160468310118,
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0.033993493765592575,
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0.011174125596880913,
0.010116519406437874,
0.018561653792858124,
0.008301317691802979,
0.0228200014680624,
0.... |
<p>I have a forecast model I am developing that uses some very unreliable input data, missing data (due to sensors or comms failures) is the rule, not an exception. The quantity being forecast is a daily average over a region, so the average of all hourly measurements from all sensors. This forecast is made just before... | g18798 | [
0.007129560224711895,
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0.0274563729763031,
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0.024365385994315147,
0.006949363276362419,
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-0.035343676805496216,
0.04274623095989227,
-0.00282044755294919,
0.04325742647051811,
0.048... |
<p>How can I obtained the estimated variance of a linear model when using R, i.e.</p>
<p>\begin{equation}
\widehat{var(y)}.
\end{equation}</p> | g61969 | [
0.00830687116831541,
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0.0069924937561154366,
0.0026562372222542763,
0.02956615947186947,
0.011791259981691837,
0.004983292426913977,
-0.016038311645388603,
-0.057284194976091385,
0.004977129399776459,
-0.01766136661171913,
0... |
<p>I am trying to better understand better the Gelman/Rubin measure of convergence of MCMCs. The method starts off by defining two quantities: $B$ and $W$. $B$ is said to be the between chain variance (as typically $m$ chains are run in parallel), and $W$ is the average within chain variance. I understand $W$ - it is m... | g61970 | [
0.039734456688165665,
0.027113787829875946,
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0.0006883916212245822,
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0.06129360944032669,
0.01609344594180584,
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-0.0440404936671257,
0.0032516969367861748,
0.019612740725278854,
0.006158551666885614,
0.0... |
<p>I am trying to measure and quantify risk, variance, and standard deviation over a time period $T$. It is broken into two sub-periods $t_1$ and $t_2$. $X_1$ is the time series for $t_1$, and $X_2$ is the time series for $t_2$, where $t_1+t_2=T$. We can assume the $X_1$ and $X_2$ are sub-time series of a longer time s... | g61971 | [
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0.0012287510326132178,
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0.006136767566204071,
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0.011351391673088074,
0.012440500780940056,
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0.015032755210995674,
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0.025860758498311043,
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0.0... |
<p>I was under the impression that the smooths fit with <code>mgcv</code> were made identifiable through a sum to zero constraint - i.e. if one was to sum the smooth over the values of its covariates, it would equal zero. This <a href="http://stats.stackexchange.com/questions/33785/centering-constraints-for-regression-... | g61972 | [
0.027312278747558594,
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0.0508754588663578,
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<p>There are 20 individuals who get tested for a particular task on 3 consecutive days. They are considered to be iid. These results are stored in a 60 element vector.</p>
<p>There is a similar test on 3 consecutive days for a different task involving the same 20 people producing a 60 element vector.</p>
<p>I would l... | g49203 | [
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0.071373850107193,
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0.03447305038571358,
0.03364663943648338,
0.030859986320137978,
-0.006703103426843882,
-0.0... |
<p>I have a large dataset, lets say 500 lines of data. As a quick workaround to higher order regression I've made educated guesses about what higher order terms I would expect in my regression equation. I've then included these as separate variables in my linear regression. For example:</p>
<pre><code>x(1) = x(1)
x(2)... | g61973 | [
0.005799469538033009,
-0.04773104190826416,
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0.028279200196266174,
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0.03487928956747055,
0.06560727208852768,
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-0.06290175765752792,
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0.04085942730307579,
0.03966044634580612,
-0.013... |
<p>The purpose to run regressions for butterfly richness again 5 environmental variables is to show the importance rank of the independent variables mainly by AIC.</p>
<p>In non-full models, they reveal that variable A tends to be more influential than the others by delta AIC.</p>
<p>However, in the full model, the r... | g61974 | [
0.009109176695346832,
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0.04446928948163986,
0.0062908814288675785,
0.04332997277379036,
0.02304142154753208,
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0.010321032255887985,
0.04188588261604309,
0.... |
<p>I have test subjects answering questions, the data will be quantitative. The questions can be divided to four categories by two factors that have two levels. For each question a factor A, B, A and B or none are "active". So each subject answers one of these four questions.</p>
<p>I am interested in how the factors ... | g18803 | [
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0.009828312322497368,
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0.02792578935623169,
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0.020849669352173805,
-0.004049387294799089,... |
<p>I'm posting this question for someone. He has the model:</p>
<p>(1) $Y_{it} = a + b X_{1,it} + c X_{2,it} + d X_{3,it} + e_{it}$</p>
<p>$i = 1,2,...,N;\phantom{...} t = 1,2,3,4,5,6,7$</p>
<p>Variables are approximately normal and we suspect no violation in OLS assumptions. The coefficient estimates are not su... | g18805 | [
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0.054545361548662186,
0.022373748943209648,
0.02169559709727764,
0.03385264798998833,
0.0... |
<p>I am trying to determine the correct amount of variance explained by each mode of an Empirical Orthogonal Function (EOF) analysis (similar to "PCA") as applied to a gappy data set. (i.e., containing NaNs). The following question builds on an <a href="http://stats.stackexchange.com/questions/34698/why-are-eigen-and-s... | g18806 | [
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0.028981314972043037,
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0... |
<p>Let's say that I have to chose the best model to predict a variable but my sample size is small. I would like to resample my data using the bootstrap, run each model and evaluate its prediction error with cross validation on each bootstrap sample. In the end I will chose the model with the lowest average prediction ... | g61975 | [
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0.011048202402889729,
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0.03267204761505127,
0.05310560390353203,
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0.012219724245369434,
0.00... |
<p>I'm trying to assess the influence of fertilisation and irrigation on biodiversity in a complete randomized block design. I have two treatments, one control and two blocks. Treatments went on for three years so I have three repeated measures. I want to find out if biodiversity is significantly different for the trea... | g61976 | [
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0.03685324266552925,
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0.049329761415719986,
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0.04... |
<p>Consider random variable $X$ with continuous, increasing CDF $F_X (x)$. Let $W=F_X (X)$. Characterize the distribution of $W$.</p>
<p>I get $F_W (w)=\mathrm{Pr}(F_X (X) \leq w)=\mathrm{Pr}(X\leq F_X^{-1}(w))=F_X(F_X^{-1}(w))=w$</p>
<p>Can I just impose that $w=1$ and say this is a degenerate distribution? That see... | g49630 | [
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<p>I am looking for a certain type of mutation (DNA base A going to DNA base B when it is followed by C) in a dataset of 24 samples. I've noticed that this has happened 3 times out of the 4 times a gene has been mutated in the dataset (1 mutation per sample). I've also got counts of how many times that kind of mutation... | g61977 | [
0.02951556071639061,
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<p>I am looking for a R package that can do multiple imputation on 2 sets of data in the same fashion. That is, I would like to multiply impute the training set and then impute the test set in the same way the training set was done. I have looked at <code>Amelia</code> and <code>mice</code> and others but can't figur... | g61978 | [
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0.03474018722772598,
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0... |
<p>I have a question on multiple imputation where one variable is the sum of several sub-groups. I have about 5 variables with a significant level of missingness. However I have a sixth variable which is the sum of the 5 sub-groups and it is missing considerably fewer observations. To give you an idea of data struct... | g274 | [
0.022563310340046883,
-0.01777004823088646,
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0.013990714214742184,
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0.... |
<p>How can I compare correlation maps independently to the number of clusters in terms of measuring the 'quality' of well separating (uncorrelated) clusters, i.e. a criterion to maximize the intra-cluster agreement and the inter-cluster disagreement? </p> | g61979 | [
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... |
<p>What is the purpose of working on a logit scale in partial dependence plots (in binary classification)?</p>
<p>One could simply go about as follows:</p>
<ol>
<li>Grow a forest</li>
<li>Suppose <code>x</code> has <code>v</code> distinct values in the training data set. Construct <code>v</code> data sets as follows.... | g18809 | [
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... |
<p>When modeling rare events with logistic regression, oversampling is a common method to reduce computation complexity (i.e., keep all the rare positive cases but just a subsample of negative cases). After model fitting, adding a offset to the intercept term is a common method to correct the event probability to refl... | g61980 | [
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0.004978029057383537,
0.019954662770032883,
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0.0... |
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