question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p><img src="http://i.stack.imgur.com/HlAfJ.jpg" alt="enter image description here"></p>
<p>The above image represents an article's page views over time. X axis is days with 9 being the most recent day. The y-axis is number of pageviews. I'm looking for a decent, not to complex either physics or statistical calculatio... | g60893 | [
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<p>Does any know the reference/link where i can find the MATLAB implementation of gap statistics for clustering as mentioned in <a href="http://gremlin1.gdcb.iastate.edu/MIP/gene/MicroarrayData/gapstatistics.pdf" rel="nofollow">this</a> paper?</p> | g60894 | [
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<p>Recently, I read <a href="http://jco.ascopubs.org/content/27/18/2931.long" rel="nofollow">an article regarding the association between age and
lymph node metastases</a>.</p>
<p>The authors stated that:</p>
<blockquote>
<p>"Because a nonlinear relationship
between age and lymph node involvement
was expected b... | g46917 | [
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<p>After testing some cases, it appears to be true that if you create partitions in a dataset, average the data in the partitions, then average the averages, you get the same result as if you averaged the entire dataset. </p>
<p>For instance:</p>
<p>avg(1,3,5,8,4,2) = 3.8333
avg(1,3,5) = 3
avg(8,4,2) = 4.6667
avg(3, ... | g60895 | [
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<p>Suppose we have a very simple online k-means where each new data-point is assigned to its nearest center (the mean is updated incrementally). Each center (cluster) is labelled with the most common label of data-points assigned to that cluster. In this special configuration: is it possible to compute a sort of "poste... | g44881 | [
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<p>I have some categorical data from a clinic taken over a year long time period. The plan is to perform a Pearson's Chi Squared test (of independence) on this data.</p>
<p>I am extracting data from a clinic's database and my aim is to see if male patients are more likely to cancel their appointment than female patien... | g60896 | [
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<p>I was fiddling with my independent variables in a linear model and I note how the y-intercept becomes 0 when all the variables become standardized. Intuitively I understand that I'm shifting the line by changing with the mean of the normal distributed variables, but I was wondering if there is some more rigorous/the... | g46433 | [
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<p>Any idea why we don't use significant digits in statistics? Something along the line of we are using estimates so rules about precision don't apply ;) ?</p> | g46921 | [
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<p>I've been using the <code>KernSmoothIRT</code> module in R to do non-parametric analysis of some items. </p>
<p>I'm trying to find a way to quantify the difficulty and discrimination of a particular set of items. What is the best way to do this with this module? </p>
<p>Geometrically, I think I'm looking for the... | g17223 | [
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<p>If I have 24 temporal covariance matrices (say monthly covariance matrices computed from daily returns of all the SP500 stocks), and I compute 24 betas for variables x and y for every month for past 2 years. Then,</p>
<ul>
<li>What is then the best estimator of beta (e.g. equally or exponentially weighted average o... | g60897 | [
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... |
<p>Actually I want to add volume traded of a stock in my Garch(1,1) model to forecast the volatility.In Matlab I can specify the model as garch(1,1) and then use estimate and forecast commands.But I am not sure how to specify my volume augmented garch(1,1) model in Matlab.</p>
<p>Any help on this would be very appreci... | g60898 | [
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<p>I'm looking for R packages implementing some new PCA methods. </p>
<p>The first one is the Stable Principal Component Pursuit method
of <a href="http://statweb.stanford.edu/~candes/papers/StableRPCA.pdf" rel="nofollow">Zhou <em>et al.</em> (2010)</a>. </p>
<p>The second one is the PCA via Outlier Pursuit algorith... | g60899 | [
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<p>As far as I know, decision trees are always used with labeled data to learn rules which differentiate between different labels. But is there anything called unsupervised decision tree? Say I have an unlabeled dataset and I want to find rules of the form $x_1 > 2\; AND \; x_2 > 4$ which <em>best</em> cluster th... | g60900 | [
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<p>I have 149 locations that are lined up from east to west. I have the geographical distances between each location and the adjacent location going west. I want to test whether the locations are randomly distributed or not. Therefore, I take the furthest west location and the furthest east location, and generate 145 r... | g60901 | [
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<p>I use R to make neat graphs that I use in Microsoft Office documents. According to <a href="http://blog.revolutionanalytics.com/2009/01/10-tips-for-making-your-r-graphics-look-their-best.html">this page</a>, the best quality is obtained with the PDF driver. Unfortunately, Word doesn't support importing PDF figures. ... | g60902 | [
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<p>I have a large amount of vegetation data that has been broken down into 13 habitat classes. I am trying to determine which vegetation tends to fall into or is absent from which habitat with any sort of significance. I have been put onto running a multinomial logistic regression, specifically using glmnet (as I have ... | g60903 | [
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<p>I came across a reference to a "Supersmoother" algorithm that was applied to prices in a timeseries.</p>
<p>Does anyone know of a tutorial in Python or whether Pandas has such a capability? </p> | g60904 | [
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<p>after doing the linear mixed model with lme4, I have used lsmeans for pairwise comparison with this command:</p>
<pre><code>lsmeans(lmer52, pairwise~color, adjust="tukey")
</code></pre>
<p>I am not sure if it is "multiple pairwise comparisons, using Least Squares Means
(LSMEANS) and Tukey's adjustment". Anyone ha... | g17227 | [
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<p>I am now reviewing a paper in which the authors decided to predict a DV through linear regression using, beyond other variables, dummy variables obtained from a tertile split of continuous variables, which were not normally distributed. In other words, for example, they took a not normally distributed variable, spli... | g60905 | [
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<p>I'm reading about SVM and I learned that we use a kernel function so the data become linearly separable in the high dimensional (vector?) space. But then I also learned that they use the soft-margin idea. But my question is why to use a soft-margin if the data is going to be linearly separable anyway in the high spa... | g17229 | [
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<p>I want to plot interaction between two variables in SAS. One is continuous and the other is binary.</p> | g60906 | [
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<p>I look at mean and standard deviation of various map like data and each give meaningful information but sometimes they provide different information. </p>
<p>For example, let's take states in a country. One state has higher mean than others but the standard deviation by itself looks OK since individual points from ... | g60907 | [
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<p>I'm quite new to the mixture models and I hope you'll help me to understand how they work. </p>
<p>Suppose I have a univariate continuous random variable <strong><em>x</em></strong> which represents time of a visit, and suppose that <strong><em>x</em></strong> is multimodal, i.e. it is described by more than one pr... | g60908 | [
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<p>I have a 1D data set with 83163 data points, and I would like to know whether the data follows a normal distribution.</p>
<p>I tried using shapiro.test and ks.test in R:</p>
<p>d is a vector containing the data</p>
<blockquote>
<p>shapiro.test(sample(d, 5000))</p>
</blockquote>
<pre><code> Shapiro-Wilk norm... | g60909 | [
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<p>I've built a random forest model (regression model) using randomForest package in R, and I calculate the correlation between the predicted values and the actual ones in order to know how the trained model is going to perform, which is very high in my case, so I was wondering in such case how this correlation is buil... | g60910 | [
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<p>I am looking to model some data, but I am not sure what type of model I can use. I have count data, and I want a model that will give parametric estimates of both the mean and the variance of the data. That is, I have various predictive factors and I want to determine if any of them influence the variance (not jus... | g17231 | [
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<p>I have some data which I've analyzed using Kaplan Meier estimation. However, I have a gut feeling that this estimator is biased due to the high censoring rate in my data (nearly 50% censored at later times). What are some ways to address this in an analysis?</p> | g60911 | [
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<p>I am calculating the age of lake sediments at the base of a sediment core by dividing the total sediment mass of the core ($\mathrm{mg} \ \mathrm{cm}^{-2}$) by the sediment accumulation rate ($\mathrm{mg} \ \mathrm{cm}^{-2}\ \mathrm{y}^{-1}$). </p>
<p>Both the sediment mass and the accumulation rate have variatio... | g60912 | [
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<p>I'm working with a team that is pressing hard to do a conjoint analysis on what is essentially a 2x2 factorial design. I get the feeling, though, that this is just their favourite hammer and not necessarily a good idea, so I'd like to push back in an informed way. What assumptions does a conjoint analysis make abo... | g60913 | [
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<p>Some Regression doubts..</p>
<p>Say, I want to quantify the difference in the effect of BMI in onset age of diabetes for Hypertensive and non-hypertensive patients.
I have done Multiple Linear Regression model with Age at onset of diabetes as outcome variable and BMI during diagnosis (continuous variable) and gende... | g49605 | [
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<p>My dataset contains two (rather strongly correlated) variables $t$ (runtime of algorithm) and $n$ (number of examined nodes, whatever). Both are strongly correlated by design, because the algorithm can manage roughly $c$ nodes per second.</p>
<p>The algorithm was run on several problems, but it was terminated if a ... | g60914 | [
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<p>I have a binary logistic regression with Y (a disease) and 5 independent variables (and some of their 2-sided interactions which did not cause multicollinearity). All of my single IVs significantly predict Y:</p>
<ol>
<li>A: <strong>positive</strong> beta for males (males are more likely to get affected)</li>
<li>B... | g49606 | [
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-0.05117769166827202,
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0.04712076112627983,
0.04913138598203659,
0.01... |
<p>Does anybody know what the formula for Cook's distance is? The original Cook's distance formula uses studentized residuals, but why is R using std. Pearson residuals when computing the Cook's distance plot for a GLM. I know that studentized residuals are not defined for GLMs, but how does the formula to compute Cook... | g46946 | [
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<p>I'm running a binary logit regression where I know the dependent variable is miscoded in a small percentage of cases. So I'm trying to estimate $\beta$ in this model:</p>
<p>$prob(y_i) = 1/(1 + e^{-z_i})$</p>
<p>$z_i = \alpha + X_i\beta$</p>
<p>But instead of the vector $Y$, I have $\tilde{Y}$, which includes so... | g60915 | [
0.025492282584309578,
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0.02018827758729458,
0.00917067937552929,
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0.025... |
<p>I have been running correlations for a set of data and several subsamples.
During this analysis I ran into a situation where the $r^2$ for two groups was smaller in each individual group as opposed to when they are grouped together. </p>
<ul>
<li>Is there any straight forward explanation for how this could happen?... | g48869 | [
0.015371738001704216,
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<p>I was looking at CrossValidate archives as well as r-archives and crantastic...for a package that has a robust approach to generalized additive models. I found two packages "robustgam" and "rgam" but their implemented functions
cover only binomial and Poisson distributions (pls correct me if I am wrong).</p>
<p>I ... | g60916 | [
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<p>Is the number of hydrogen bonds or the number of rings in a molecule a discrete or a continuous variable ? </p>
<p>Can I say that the number of rings: 1, 3, 4, $\dots$ is a continuous variable because in theory this number could rise up to infinity? </p>
<p>On the other hand it can only take integer values so....i... | g60917 | [
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<p>Given a time series, I'd like to estimate the parameters of an AR(1) model for it. <a href="https://en.wikipedia.org/wiki/Autoregressive_model#Estimation_of_AR_parameters" rel="nofollow">As explained on wikipedia</a>, there are different ways for doing that. What may be called a naive method is to compute the samp... | g60918 | [
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<p><strong>The case:</strong> I am trying to estimate event history models (also known as survival models) with time-varying predictors at two different levels of (geographical) aggregation. More precisely, I am using a discrete time event history model (logit model on stacked data) to predict the odds of outmigration ... | g60919 | [
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<p>I have a dataset (y vs. t) that I think is best described by:</p>
<ul>
<li>Slight initial downward slope</li>
<li>At maybe t = 1 or 2, steep downward slope</li>
<li>Asymptote at y = 0</li>
</ul>
<p><img src="http://i.stack.imgur.com/85kvc.png" alt="enter image description here">
<img src="http://i.stack.imgur.com/... | g17248 | [
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<p>Forgive me if I've missed something rather obvious. </p>
<p>I'm a physicist with what is essentially a (histogram) distribution centered about a mean value that approximates to a Normal distribution. The important value to me is the standard deviation of this Gaussian random variable. How would I go about trying to... | g17249 | [
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<p>I understand that ,usually, time-series studies do not aim to provide a causal explanation of anything but rather aim to forecast. In which case it does make sense that most time series studies aren't concerned with omitted variable bias. </p>
<p>However, I've come across a time series study that seeks to explain S... | g17250 | [
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<p>I am trying to solve a problem for my thesis and I don't see how to do it. I have 4 observations randomly taken from a uniform $(0,1)$ distribution. I want to compute the probability that $3 X_{(1)}\ge X_{(2)}+X_{(3)}$. $X_{(i)}$ is the ith order statistic (I take the order statistic so that my observations are r... | g174 | [
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... |
<p>Today, I was trying to use probabilities to make an 'everyday' (and not very important) decision... but I found that I'd forgotten how to approach this sort of problem (if I am correct in believing that I ever knew how to deal with a problem like this).</p>
<p>Here is the form of the problem I was trying to solve:<... | g17251 | [
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... |
<p>I want to see if an interaction variable in a multiple regression is significant for the whole sample, and then just for men and just for women. When I created the interaction variable for the whole sample, I centered the interaction components by subtracting the mean for the whole sample. </p>
<p><strong>Now, when... | g17253 | [
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0.034572284668684006,
0.002... |
<p>I'm trying to find a statistical test that can help me compare the means of two dependent groups. </p>
<p>My data: </p>
<ol>
<li>parameter values from white matter region in an in vivo rat brain </li>
<li>parameter values from white matter region in the same rat brain, bur after the tissue has been fixated.</li>... | g60920 | [
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<p>In my case, I have a dataset of observations which have not been produced by an HMM meaning that I do not know what kind and how many hidden states should exist there.
So, the only known factor are the observations.
After the training of my model using a specific number of hidden states each time, I needed then to ... | g60921 | [
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... |
<p>Suppose I roll a six-sided die 1000 times and write down the number of times each face comes up. How do I test whether the die is fair? Can I use a chi-squared test where the expected number of each face is 1000/6=167?</p>
<p>There also appears to be a <a href="http://en.wikipedia.org/wiki/Multinomial_test" rel="... | g49607 | [
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0.011205012910068035,
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0... |
<pre><code>Variables:
lprice = log(price of house)
ldist = log(distance from incinerator)
lintst = log(distance from interstate)
</code></pre>
<p><strong>1st regression</strong></p>
<p><img src="http://i.stack.imgur.com/tIGT5.png" alt="1st reg"></p>
<p><strong>2nd regression:</strong></p>
<p><img src="http://i.stac... | g49359 | [
-0.028273021802306175,
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0.06552111357450485,
0.11144200712442398,
-... |
<p>There are several approaches, for example, moderated regression analysis and Hunter, Schmidt and Jackson. The HSJ (1982) approach invokes true variance computation based on subsets say male- vs female-led studies. According to Hunter, J. E., Schmidt, F. L. and Jackson (1982) <em>Cumulating Findings Across Studies</e... | g60922 | [
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0.027615712955594063,
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0.06972135603427887,
0... |
<p>I have these data:</p>
<pre><code>set.seed(1)
predictor <- rnorm(20)
set.seed(1)
counts <- c(sample(1:1000, 20))
df <- data.frame(counts, predictor)
</code></pre>
<p>I ran a poisson regression</p>
<pre><code>poisson_counts <- glm(counts ~ predictor, data = df, family = "poisson")
</code></pre>
<p>An... | g60923 | [
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... |
<p>I'm reading an article where the author fits a Poisson regression on some data. Some of the covariates (but not the outcome) are partially missing. The author writes that he:</p>
<blockquote>
<p>conducted the analysis using a valid, reasonably efficient method for handling missing-at-random data.</p>
</blockquote... | g60924 | [
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... |
<blockquote>
<p>Two containers $A$ and $B$ are placed adjacently to each other and gas passes through a small aperture joining them. </p>
<p>A total of $N(>1)$ molecules is distributed among the containers.</p>
<p>Assume that at each epoch of time one molecule, picked uniformly at random from the $N$ ava... | g60925 | [
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... |
<p>My lab teacher asked this question in class, but i find no way to work it out.</p>
<p>If I have $n$ points with their uncertainties, I know that they follow a linear expression and I find the best-fit line of them, is there a way to predict how many points will be crossed by the line? </p>
<p>I thought that this n... | g60926 | [
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<p><a href="http://arxiv.org/ftp/arxiv/papers/1312/1312.1520.pdf" rel="nofollow">Face Recognition approach based on entropy
estimate of the nonlinear DCT features</a> proposes to use maximum entropy estimate of the DCT of the pixels. My question is maximizing entropy would mean minimizing information content since entr... | g60927 | [
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-... |
<blockquote>
<p>Suppose the weather condition classified as "sunny" (S) or "rainy" (R). Assume the condition on day $n + 1$ is dependent on the days $n$ and $n-1$ only. Work out the transition matrix from the table below.</p>
<p>$$\pmatrix{\mathrm{Yesterday} & \mathrm{Today} & \mathrm{Tomorrow} \\ R &... | g60928 | [
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... |
<p>A newbie question (please provide detailed answers):
I am trying to use the Kolmogorov–Smirnov test. I managed to calculate the difference between the empirical points and the theoretical distribution $D$ (following <a href="http://en.wikipedia.org/wiki/Kolmogorov%E2%80%93Smirnov_test#Kolmogorov.E2.80.93Smirnov_stat... | g60929 | [
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-0.02353416383266449,
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0.07920623570680618,
0.... |
<p>I am currently doing a research on effects of writing styles on the perception of reader.</p>
<p>Currently I have the following 4 groups</p>
<pre><code>Group 1: Pre Test - Treatment 1a - Post Test
Group 2: Pre Test - Treatment 1b - Post Test
Group 3: Pre Test - Treatment 2a - Post Test
Group 4: Pre Test - Treatmen... | g38015 | [
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... |
<p>I have 3 measurement points, N=4000, N=2000, N=3000 (week 0, week 6, week 12). </p>
<p>My goal is to estimate the relative importance of 14 regressors on one dependent variable. Now I can do that separately for each time point, but the N are comparably small to estimate relative regressor importance with such a hug... | g60930 | [
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0... |
<p>I have the following categorical/count data :</p>
<pre><code>Category A1 | Category A2 | Category B1 | Category B2 | Category C1 | Category C2 | Category C3 | User Population 1 | Video Count 1 | Ad Count 2
0 | 1 | 1 | 0 | 0 | 1 | 0 | ... | g60931 | [
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<p>What is a good book that covers mixed distributions? </p>
<p>Most statistics books either only briefly mention them or do not cover the topic at all. </p>
<p>I'd like to have a comprehensive resource covering issues of joint distributions with both discrete and continuous variables, conditional and marginal distri... | g46972 | [
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-0.02... |
<p>The augmented Dicky-Fuller test, as described in Tsay's Financial Time Series:</p>
<p><img src="http://i.stack.imgur.com/JABsG.png" alt="enter image description here"></p>
<p>The regression done in the test seems to only produce real value $\hat{\beta}$, so it seems to me the test only tests existence of root 1 or... | g60932 | [
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0.012649854645133018,
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0.004811154678463936,
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... |
<p>In time series, after fitting a AR(p) model to a time series, when checking the fitted model, we will apply Ljung-Box test on the residual series.</p>
<p>In Tsay's Financial Time Series, there is a goodness-of-fit measure $R^2$:</p>
<p><img src="http://i.stack.imgur.com/rEynU.png" alt="enter image description here... | g60933 | [
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<p>Say I have to mix <strong>n</strong> double Truncated Normal distributions $\textit{TNormal(μ,σ$^{2}$,0,1)}$. Furthermore, each distribution has a weight <strong>w</strong>. <strong>w</strong> represents the influence of the distribution in the mixture: the greatest <strong>w</strong>, the greatest is its influence ... | g60934 | [
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<p>I could not pick a more generic title for this question I guess. Here is what I am dealing with:</p>
<p>I have a time series data stream coming in from multiple measurement endpoints. The number of endpoints is between 2 to 200. The resolution is 10 seconds but I am using the 1 minute aggregate. The data is CPU uti... | g60935 | [
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<p>If an ARMA process (or just a AR(p) process) has real unit roots (i.e. 1 or -1), then differencing it repeatedly will make the differenced process weakly stationary.</p>
<p>An ARMA process (or just a AR(p) process) may have complex unit roots. If that happens, can repeatedly differencing make the differenced proces... | g60936 | [
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<p>This is a more "statistical" version of my <a href="http://math.stackexchange.com/questions/31267/mean-chord-length-in-a-convex-polygon"> Math.SE problem </a>.</p>
<p><b> Question </b> Let $\mathbf{P}$ be a convex polygon of $m$ sides. Pick two of its edges at random, and further pick a random point on each of the... | g60937 | [
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<p>a journal article has a method for designing experiments to be fit to a 4-parameter logistic model. The model used is $y= D + \frac{A - D}{1 + (\frac{x}{C}) ^ B}$<br>
A = upper asymptote<br>
B = maximum slope<br>
C = x value when y = 50% of maximum (i.e. 1/2 of upper asymptote)<br>
D = lower asymptote<br>
Using pil... | g46977 | [
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<p>I'm given an $n\times n$ grid of positive integer values. These numbers represent an intensity that should correspond to the strength of belief of a person occupying that grid location (a higher value indicating a higher belief). A person will in general have an influence over multiple grid cells. </p>
<p>I believe... | g60938 | [
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<p>I did a correlation analysis for my variables. All of them are associated (the coefficient is above 0). However, there is no collinearity problem in my regression analysis. I do not know how to explain it? I think I am confused about correlation and collinearity analysis...but if coefficient is above 0, it shows the... | g60939 | [
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<p>I have two samples set, one is positive, and the other is negative. But, in each of both sets, there are some outliers that don't belong to it. Can the Robust subspace clustering be used to help me refine the two datasets and remove the outliers. I just want those most probable samples to be left. Maybe the Mixture... | g60940 | [
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<p>I recently <a href="http://stats.stackexchange.com/questions/78255/how-to-resolve-simpsons-paradox">asked a question</a> about Simpson's paradox. Suppose we are concerned about making some choice about an arbitrary element of a population. Recall that Simpson's paradox arises when the answer suggested by the aggrega... | g60941 | [
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<p>I need to know how to get the number of people needed in a survey for a 99% confidence level, within 1 person? And the only given is the population standard deviation of 15.4.</p> | g60942 | [
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<p>What does mutual information (MI) convey? Looking for good reference books on information theory</p> | g17284 | [
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<p>Let assume I have a dataset like this <a href="http://archive.ics.uci.edu/ml/datasets/Adult" rel="nofollow">dataset</a> where there are several textual attributes even continuos attributes like age. I have always encountered cases where k-nn is applied on just two attributes and all of those ones numerical. How can ... | g141 | [
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<p>I'm trying to fit an ARIMA model to housing data set.
Playing around with the p's and q I was able to get an ARIMA Model (2,1,2,)(2,0,0) with an AIC value of AIC=4946.76
I used auto.arima to see if I picked the best model. auto.arima picked the (2,1,3)(2,0,0) model that had an AIC value of AIC=4948.21 .</p>
<p>Then... | g17285 | [
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<p>I need help on determining what tests to use in SPSS. Let me provide some background on my research:</p>
<ol>
<li>I am doing a research on system automation of leave management in a company (which is still using a manual paper form to apply for leave).</li>
<li>My hypothesis validates the automation of the differen... | g17286 | [
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<p>I am running a structural equation model (SEM) in Amos 18. I was looking for 100 participants for my experiment (used loosely), which was deemed to be probably not enough to conduct successful SEM. I've been told repeatedly that SEM (along with EFA, CFA) is a "large sample" statistical procedure. Long story short, I... | g37600 | [
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<p>Let's say you want to cluster some objects, say documents, or sentences, or images.</p>
<p>On the technical side, you first represent these object somehow so that you could calculate distance between them, and then you feed those representations to some clustering algorithm.</p>
<p>Externally, however, you just wa... | g46998 | [
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<p>I have some parameter estimates and confidence intervals estimated from a set of model-averaged binomial GLMMs: two main effects and their interaction. I would like to plot [population level] fitted values for the main effects and their interaction, as well as 95% confidence bands. I can plot the population level fi... | g17289 | [
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<p>I was going through OpenIntro Statistics[http://www.openintro.org/stat/textbook.php] and came across two case studies in the first chapter</p>
<ol>
<li>Discrimination against women during promotion - Page 42</li>
<li>Stanford Heart Transplant study - Page 65</li>
</ol>
<p>How can shuffling of cards determine indep... | g60943 | [
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<p>I have the problem of proofing that </p>
<p>$$X=(1/\sigma^2) \sum_{i=1}^{n} Y_i ^2$$</p>
<p>where $Y_i \sim N(0,\sigma^2)$ is $\chi_n ^2$ distributed with $E(X)=n$:</p>
<p>My proof that $E(X)=n$:</p>
<p>$$E(X)=E((1/\sigma^2) \sum_{i=1}^{n} Y_i ^2)= $$
$$\sigma^2=\sum_{i=1}^{n}(E(Y) - \bar Y)$$</p>
<p>$$E(X)=E((... | g17291 | [
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<p>I am a finance student and in finance we measure the risk of different financial items like stock prices, earnings, and cash flows etc. we measure this risk either through standard deviation or through ARCH/GARCH and we can generate its series. the main idea behind my question is that I want to check whether risk as... | g60944 | [
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<p>I need a single imputed dataset (e.g. to create a country group dummy from the imputed country per capita income data). R offers packages package for creating multiple imputed data (e.g. Amelia) and combining results from multiple datasets (as in MItools). My concern is if I can average all the imputed data to obta... | g17294 | [
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<p>Sorry, I'm a huge statistics noob.
I'm looking to find the probability that a certain event occurs in a binomial experiment. I take a few thousand samples per test, and then calculate the probabilities. The problem is that the experimental probabilities keep varying by a small amount. So I've started plotting the e... | g60945 | [
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<p>I'm quite new to machine learning and a bit unsure about the whole process and the interpretation of the results.</p>
<p><strong>The Task:</strong>
I have images with some objects of somewhat the same color and shape which overlap and I want to segment the single objects using machine learning to get the edges of a... | g60946 | [
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<p>I have a panel dataset with a sample of 800 groups, each having between 200-500 observations. The data looks like this:</p>
<p><img src="http://i.stack.imgur.com/UNfSo.png" alt="enter image description here"></p>
<p>The dependent variable is binomial: <code>close_gp30_f30</code>.</p>
<p>The independent variables ... | g17297 | [
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<p>I have a dataframe with each row being a different site (51 sites), and each column being mean values of a different continuous environmental variable (19 variables).</p>
<p>I am trying to calculate a measure of environmental similarity/dissimilarity by using a distance calculation between sites.</p>
<p>I would li... | g60947 | [
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<p>A guy got 88 in his test which has mean score of 64 with SD 8. He missed the second exam in which the meanscore was 45 and SD was 5. He got a prorated marks of 55. The prof used regression to get his second test marks. What was the corelation between 2 exams ? </p>
<p>$$
\hat{z}_y = r z_x
$$</p>
<p>and i calculate... | g60948 | [
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<p>I have the following interpretation of the Bayesian probability and inference (without referring to Measure Theory, I am still at the very beginning of learning it): Let's say we have five random variables $x_1,x_2,x_3,x_4,p$ given as in the following graphical model:</p>
<p><img src="http://i.stack.imgur.com/E5Bnr... | g60949 | [
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<p>I am doing research on mortality. I am running Cox regression and I am adjusting for 40 variables which are proven in the literature to be related with mortality. My main exposure is X. In my final model I have 19 variables that are significant and my exposure is non significant. Than I try the last analysis includi... | g47011 | [
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<p>I'm looking for a good Java library implementing several clustering algorithms.</p>
<p>I'll have to cluster some programs execution traces and I still don't know which algorithms I am going to need, so I'd like to use a library providing lot of them and that makes it easy to swap algorithms.</p>
<p>So far I had a ... | g17303 | [
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... |
<p>I am fitting a simple linear regression model with 4 predictors:</p>
<p><code>lm(Outcome ~ Predictor1 + Predictor2 + Predictor3 + Predictor4, data=dat.s)</code></p>
<p>I'm finding that the model predictions are consistently off as shown in this graph:
<img src="http://i.stack.imgur.com/CNLJz.png" alt="scatterplot ... | g60950 | [
0.02913566865026951,
-0.06274303793907166,
-0.00859049055725336,
0.016766812652349472,
0.029486602172255516,
0.011451123282313347,
0.02213367074728012,
0.019944895058870316,
-0.0676385834813118,
-0.02374943532049656,
0.022221921011805534,
-0.023042771965265274,
0.036500513553619385,
-0.012... |
<p>I observed the following relation and would like to know where I can find a general proof for this:</p>
<p>Assume a data matrix $A = [a_{ij}]_{t x k}$. </p>
<p>1) Perform principal component analysis (PCA) using the correlation matrix $corr(A)$</p>
<p>2) Calculate the proportion od variance explained by the first... | g60951 | [
0.04455629363656044,
-0.04024882987141609,
-0.01827242225408554,
-0.10326165705919266,
0.032130490988492966,
-0.002290573203936219,
0.10001823306083679,
0.009466639719903469,
0.015701044350862503,
0.004669655580073595,
0.025698933750391006,
0.035293228924274445,
-0.009531175717711449,
0.04... |
<p>Soon I'll be sitting for a midterm (and then the dreaded final) for a graduate class in Statistics. </p>
<p>It's open book / notes but I'll be needing a calculator -- something I've not used for years.</p>
<p>Any thoughts on what features I should look for when shopping for one. I've always wanted to own and use a... | g46943 | [
-0.025231914594769478,
0.03159783035516739,
-0.012241567485034466,
-0.04294976592063904,
-0.02461872063577175,
-0.025463895872235298,
0.033779326826334,
-0.010071820579469204,
-0.03133336827158928,
-0.012747446075081825,
0.03706290200352669,
0.014481554739177227,
0.05221772938966751,
0.017... |
<p>I am running a cumulative link model on an ordered response variable that represents an assigned preference value between 0 and 4. The setup of my research is a questionnaire in which respondents are asked to rate a collaboration scenario (higher score means a more preferable scenario.</p>
<p>I already know that sp... | g8599 | [
-0.022409889847040176,
0.001565151265822351,
-0.022865861654281616,
-0.03647291660308838,
0.062207818031311035,
0.01169657800346613,
0.036267299205064774,
0.02897302620112896,
-0.050139326602220535,
-0.0045856875367462635,
0.021988604217767715,
-0.012516876682639122,
0.06451842933893204,
0... |
<p>I have a question regarding the time needed for training a classifier. I am facing the specific problem of Sentiment Analysis (classification of text as pos/neg/neu). </p>
<p>(Excepting online learning algorithms) Since the training stage of a classifier is usually conducted only once and offline, in the end does ... | g26472 | [
-0.012801796197891235,
0.0017315298318862915,
0.013006474822759628,
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0.020465131849050522,
0.06045437231659889,
-0.02297424152493477,
0.026463955640792847,
-0.026128379628062248,
0.01639558933675289,
0.015325348824262619,
0... |
<p>I am trying to estimate the following equation:
$$Y_{i,t+1}=(λβ)X_{i,t}^{'}+(1-λ)Y_{i,t}+\epsilon_{i,t+1}$$
but I don't understand how to find the $\lambda$ estimate especially since $X'$ consists of multiple variables. In this equation, $\lambda$ is a scalar and $\beta$ is a vector. Can anyone point me in the right... | g60952 | [
-0.015400209464132786,
-0.018335828557610512,
-0.0294512752443552,
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0.07036354392766953,
-0.0699034109711647,
0.0303728599101305,
0.009408380836248398,
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-0.01758250966668129,
-0.05258753523230553,
0.03435482457280159,
-0.028103115037083626,
0.0547... |
<p>I have a dataset where $x_{1}$, $x_{2}$, ..., $x_{k}$ are of mixed type and $y$ is a ranking from $1$ to $n$ where $n$ is the number of observations in the dataset. I'd like to predict $y$ based on the $x$s.</p>
<p>What is a good way to proceed here? My intuition is that a GLM approach won't be particularly useful ... | g17310 | [
0.017155930399894714,
-0.0026119230315089226,
-0.02321511320769787,
-0.018239401280879974,
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-0.03625909611582756,
-0.04044882208108902,
0.03098907880485058,
0.014295144937932491,
0.07502826303243637,
0.... |
<p>In a variation on the <a href="http://en.wikipedia.org/wiki/Coupon_collector%27s_problem">coupon collector's problem</a>, you don't know the number of coupons and must determine this based on data. I will refer to this as the fortune cookie problem:</p>
<blockquote>
<p>Given an unknown number of distinct fortune ... | g28045 | [
-0.029507653787732124,
0.05143055319786072,
0.0034082033671438694,
-0.0022772846277803183,
-0.017472723498940468,
-0.06884908676147461,
0.008461332879960537,
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0.02199021726846695,
-0.010395141318440437,
0.02336443029344082,
0.007002420723438263,
0.... |
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