question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I read on my machine learning course (on coursera) that random initialization performed several times and then taking the cluster with the lowest cose could help when the number of clusters is "small", but didn't help much for K>>10. Why so?</p> | g66832 | [
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<p>I have come across this confusion regarding why we need to add more features when our learning model is bias. I am referring to this lecture from Andrew Ng related to machine learning. I mean suppose I have data point such that they can be modeled better by a quadratic function but instead I choose a linear one</p>
... | g66833 | [
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<p>I'm new to svm and I've been looking for a svm to use. From all the ones that I've seen, the training label vector is basically a m by 1 vector of 1 and -1. I don't understand why this is so. I was under the assumption that each row of the training vector should be a unique number that labels its respective trained ... | g26065 | [
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<p>I am using JMP to find a relationship between drought index values and yearly corn yields for a 30 year period. I have drought data for seven different indeces and each index ranges from -6 (severe drought) to +6 (extremely high precipitation).</p>
<p>The drought data contains monthly drought index values for Marc... | g26066 | [
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<p>I am trying to apply MCMC on a problem, but my priors(in my case they are $\alpha\in[0,1],\beta\in[0,1]$)) are restricted to an area? Can I use normal MCMC and ignore the samples that fall outside of the restricted zone(which in my case is [0,1]^2), i.e. reuse transition function when the new transition falls out of... | g26067 | [
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<p>I am trying to sample from a posterior distribution and I only have an explicit formula for likelihood but I can sample from the prior distribution. How can I sample from the posterior distribution with such a restriction. Is there any specific method?</p>
<p>After seeing the answers I've decided to write my exact ... | g66834 | [
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<p>I would like to make meaningful interpretation from a two-way interaction data using factor analytic covariance structure. I have a genotype x environment matrix and I would like to know which environments account common source of variation from large set of environments. I would like to use mixed effect model and I... | g66835 | [
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<p>I've been working on a research project for close to five years now. For my thesis I have to show how "well" did my approach improve things. </p>
<p><strong>Setup</strong>: Every year we use a tool A to brainstorm and negotiate software requirements. The tool was wiki-based and had very low participation from techn... | g26068 | [
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<p>The definition of entropy for a continuous signal is:</p>
<p>$h[f] = \operatorname{E}[-\ln (f(x))] = -\int\limits_{-\infty}^{\infty} f(x) \ln (f(x))\, dx$</p>
<p><a href="http://en.wikipedia.org/wiki/Entropy_%28information_theory%29#Extending_discrete_entropy_to_the_continuous_case%3a_differential_entropy" rel="no... | g66836 | [
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<p>I'm using support vector regression to model some fairly skewed data (with high kurtosis). I've tried modeling the data directly but I'm getting erroneous predictions I think mainly due to the distribution of the data, which is right skewed with very fat tails. I'm pretty sure a few outliers (which are legitimate da... | g66837 | [
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<blockquote>
<p>There are two programs in a high school. Boys are a
majority (65%) in program A, and a minority (45%) in program
B. There is an equal number of classes in each of the two
programs. </p>
<p>You enter a class at random, and observe that 55%
of th... | g46475 | [
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<p>I am analyzing weather data from 2 sites, and trying to determine if they are correlated. For the most part, I am able to run linear regressions and Pearson's correlations since the data are relatively normal. However, when looking at relative humidity, it obviously has an upper limit in place (100%; it would have a... | g26070 | [
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<p>My data is a panel of countries by year. Suppose my main RHS variable is a country's GDP and my main LHS variable classifies countries by whether the country is a democracy.</p>
<p>Is it desirably to weight each observation by the country's population in a particular year? Since the world population has generally... | g26071 | [
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<p>I am obtaining confidence intervals using different bootstrap methods. When comparing them, what is does it mean to use Monte Carlo variation to look at how much the upper and lower limits vary for each bootstrap?</p> | g5505 | [
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<p>I'm a little confused here. Appreciate if anyone can help me out.</p>
<p>During a <em>k-fold</em> nested CV, I understand for each combination of training fold and testing fold , the training fold will be further split into <em>k</em> subsets and a small CV will be carried out to determine the optimal hyper-paramet... | g66838 | [
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<p>I am using the <a href="https://www.kaggle.com/c/data-science-london-scikit-learn/" rel="nofollow">Kaggle Scikit</a> data to learn R.</p>
<p>I am using the R e1071 SVM function to predict classes.</p>
<p>When I use:</p>
<pre><code>svm(train, trainLabels, scale = TRUE, type = NULL, kernel = "polynomial")
</code></... | g66839 | [
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<p>I am creating a Recommender System and want to incorporate both the ratings of "similar" users and the features of the items. The output is a predicted rating [0-1].I am considering a Neural Network (to start with).</p>
<p>So, the inputs are a combination of the features of the items and the ratings of each user. F... | g66840 | [
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<p>Need some help answering this please!</p>
<p>The price and the year of manufacture for 124 randomly selected used Mazda cars were recorded in 1992. It is desired to be able to predict the 1992 price of a used Mazda car from its year of manufacture. In order to use the method of modelling using a least-squares line,... | g66841 | [
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<p>I'm studying two geographically-isolated populations of the same species. Inspecting the distributions, I see that both are bimodal (there's some seasonality to their occurrence), but the peaks in one population are much higher and much narrower (i.e., the variance of the local peaks is smaller).</p>
<p>What sort o... | g5529 | [
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<p>This should be a fairly straight forward but I still couldn't quite get it.
Let $X$ be $n$ by $1$ random vector, $Y$ be another $n$ by $1$ and that $X$ and $Y$ are independent.
What is $Var(X^tY)=:V_{XY}$?</p>
<p>I tried generalizing this formula from the univariate case
$Var(xy)=E(x)^2Var(y)+E(y)^2Var(x)+Var(x)Var... | g66842 | [
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<p>I have data for a network of weather stations across the United States. This gives me a data frame that contains date, latitude, longitude, and some measured value. Assume that data are collected once per day and driven by regional-scale weather (no, we are not going to get into that discussion). </p>
<p>I'd like t... | g26076 | [
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<p>I have 2 non-normally distributed samples of different sizes (N1~=N2). </p>
<p>To evaluate whether there is a significant difference between these samples, I used the Mann Whitney U test (<code>ranksum</code> in MATLAB).</p>
<p>Now I want to evaluate by how much the populations differ. With normally distributed da... | g11214 | [
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<p>Trying to prove that this doesn't belong to exponential family.</p>
<p>$f(y|a)=4\frac{(y+a)}{(1+4a)} ; 0 < y < 1 , a>0$</p>
<p>Here is my approach:</p>
<p>$$f(y|a) = 4(y+a)e^{-log(1+4a)}$$
$$f(y|a) = (4y)(1+\frac{a}{y})e^{-log(1+4a)}$$</p>
<p>Comparing it with standard form, $h(y) = 4y$ and $g(a)$ whic... | g66843 | [
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<p>I'll preface my question by saying I have a very limited knowledge of statistics, and while I've put some thought into this problem, I'm a bit stuck! Onwards...</p>
<p>I have a collection of fixed-size vectors of the form $\overline{v} = \{ c_0,\ldots,c_n \}$, where each $c_i \in \mathbb{Z}^*$ and relates to an obs... | g66844 | [
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<p>I encounter it in many books as well as web. Natural Language Processing and Machine Learning are said to be different subsets of Artificial Intelligence. Why is it? We can achieve results of Natural Language Processing by feeding sound patterns to Machine Learning algorithms. Then, what's the difference?</p> | g26079 | [
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<p>I heard somewhere, that I can directly test (or gather support for) a null-hypothesis using the Bayes-Factor. In my specific experiment, I hypothesize that an experimental manipulation does not have an impact on some variable but does selectively impact another one. Somehow, simply showing that a t-test gives non-si... | g11216 | [
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<p>Does anyone know where I can find a corpus I can use to train a classifier into IPTC news categories (<a href="http://www.iptc.org/site/NewsCodes/" rel="nofollow">http://www.iptc.org/site/NewsCodes/</a>) ?
A google search was not very useful.</p>
<p>Thank you</p> | g14734 | [
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<p>Regarding a question posted <a href="http://stats.stackexchange.com/questions/24712/meta-analysis-in-r-with-multiple-snps/109049#109049">here</a>, I have the same problem and I can't figure out a solution. I started by doing my meta-analysis in PLINK, but I want the confidence intervals of the meta-analysis, which P... | g66845 | [
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<p>My causal comparative study seeks to three questions related to the hypothesis: a) is there a statistically significant difference between the academic achievement of 6th grade mathematics students based on non-band music participation status; b) is there a statistically significant difference between the academic a... | g26084 | [
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<p>I am looking into semi-supervised naive Bayes, which appears to be most commonly applied to text classification problems, such as the 20 newsgroups problem. Can anyone recommend some other benchmark datasets (preferably unrelated to problems in text classification) where semi-supervised naive Bayes works well, that... | g26086 | [
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<p>-I have ~6mo of data that contains daily weight/caloric intake & #carbs/fats/proteins. I'm trying to figure out a way to make sense of the data. It's not a perfect experiment so there are other factors I should have considered and taken into account some sort of maintenance metabolic conditions (calories/macros ... | g66846 | [
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0.06790343672037125,
0.02... |
<p>I'm having a little trouble with the proof that the expected value of $x_i$ is $ \bar{X} $.</p>
<p>What I have is </p>
<p>$E[x_i]=\sum_{j=1}^{N}X_j Pr(x_i=X_j) $</p>
<p>Then,</p>
<p>$Pr(x_i=X_j) = 1/N $</p>
<p>This is the bit I can't understand, how does that probability evaluate to that value.</p>
<p>I know t... | g49331 | [
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0.01532798819243908,
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... |
<p>I've got a binary characteristic and a population $S$ with size $n$ and $P[X] = p$ such that $p$ may be small and $n$ is extremely large. Within this population are subpopulations of various sizes $S_0, S_1, \dots, S_k \subset S$.</p>
<p>I'd like to be able to select each subpopulation in which $p_i < p$ with s... | g66847 | [
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0.0018502585589885712,
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0.046474676579236984,
0.042342692613601685... |
<p>Let $a_{1},a_{2},a_{3}$ be independent with a normal(0,1) distribution. Define $X_{1},X_{2},X_{3}$ by $X_{1}=a_{1}$, $X_{2}=\theta X_{1}+a_{2}$ and $X_{3}=\theta X_{2}+a_{3}$ Find the MLE for $\theta$ . </p>
<p>My attempt: I get that $X_{1}$ has distribution $N(0,1)$, $X_{2}$ is $N(0,\theta^2+1)$ and $X_{3}$ is $N(... | g66848 | [
0.0005322088254615664,
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0.02243521623313427,
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0.03203260898590088,
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-0... |
<p>I am interested in a histogram comparison method or histogram matching technique that takes into account only the tails of the distribution. Consider the following histograms:</p>
<p>Histogram 1:</p>
<p><img src="http://i.stack.imgur.com/LFdFD.png" alt="enter image description here"> </p>
<p>Histogram 2:</p>
<p>... | g66849 | [
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0.0001386508665746078,
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-0.03851895406842232,
0.023414332419633865,
0.027215687558054924,
0.05816587805747986,
0.0... |
<p>I have been testing the google prediction api <a href="https://developers.google.com/prediction/" rel="nofollow">https://developers.google.com/prediction/</a></p>
<p>It seems to be excellent, i gave it 5 features so it can predict a regression problem, the API fitts the data very well, however as soon as we want to... | g66850 | [
0.022715473547577858,
0.022910447791218758,
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0.0254772... |
<p>How do I implement k-medoid clustering algorithms like PAM and CLARA in python 2.7? I am currently using Anaconda, and working with ipython 2.7. I have tried scipy.clusters but they don't seem to have the above algorithms. Please help</p> | g66851 | [
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<p>In the setting of psychological experiments, where a categorical response has to be given, the same response can, in theory, be generated by different latent processes. For example, in an experiment where participants have to indicate whether a particular word was part of a word list they learned earlier, some corre... | g26095 | [
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... |
<p>I am reading this problem from DeGroot's "Probability & Statistics" 2nd edition.</p>
<p><img src="http://i.stack.imgur.com/g9gak.png" alt="enter image description here">
<img src="http://i.stack.imgur.com/2eVGj.png" alt="enter image description here"></p>
<p>I can't understand why $$\Pr[G^{-1}[F(X)]\leq z]=\Pr... | g66852 | [
0.016600262373685837,
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0.03862440213561058,
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-0.0... |
<p>I was playing with the <a href="http://cran.r-project.org/web/packages/TSA/index.html" rel="nofollow">TSA</a> package in R and wanted to test the <code>arimax</code> function to the solution provided in Pankratz's <em>Forecasting with Dynamic Regression Models</em>, chapter 8. The savings rate and the function seems... | g26097 | [
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<p>Say I wanted to investigate the proportion of different types of nuts in bags of mixed nuts. So I weigh the nuts by type. Would I be able to use the information on weights and the Chi-squared test to analyze the nuts? </p> | g46499 | [
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<p>I want your help to Apply the Bradley-Terry models on any particular sport or any other idea of an application by using R. I am not familiar with R, can anyone help me ? </p> | g66853 | [
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<p>I did hierarchical regression analysis on my data due to having moderation effects in my research model.</p>
<p><img src="http://i.stack.imgur.com/imZJq.jpg" alt="enter image description here"></p>
<p>R2 increased from .695 in model1 (main effect only) to .734 in model2 (main &interaction effects)(sig. F chang... | g26098 | [
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<p>Suppose you have two normally distributed, independent random varianbles X and Y, where X has mean $\mu _x$ and variance $\sigma^2 _x$ and Y has mean $\mu _y$ and variance $\sigma^2 _y$.</p>
<p>For each, $\mu \gg \sigma^2$ and $\mu \gg 0$.</p>
<p>We know from sampling that the distribution of $X/Y$ is approximatel... | g66854 | [
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0... |
<p><strong>Problem</strong></p>
<p>I would like to plot the variance explained by each of 30 parameters, for example as a barplot with a different bar for each parameter, and variance on the y axis:</p>
<p><img src="http://i.stack.imgur.com/AERls.png" alt="alt text"></p>
<p>However, the variances are are strongly sk... | g46502 | [
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0.04361090436577797,
... |
<p>I want to test if there is a rivalry among two siblings in a family. I have 15 questions in my study and I let my 100 respondents ( distributed equally to two siblings) ranked them 1 to 15. </p>
<p>How should I analyse this data?</p> | g26099 | [
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0.041069142520427704,
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-0.018576450645923615,
0.003450523130595684,
0.022642923519015312,
0.00896688923239708,
... |
<p>I have a (I suspect) simple question. I have time series cross section data on voting behaviour in the Council of the European Union (the monthly number of yes, no and abstentions for each member state from 1999 to 2007). So basically the variables are counts, thus a Poisson/negative binomial regression would be app... | g66855 | [
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... |
<p>Anyone know why when you run a SEM model in SAS using proc calis (or tcalis) you do not get p-values for the parameter estimates? It does supply a t-value however.</p>
<p>Two popular SEM packages in R, 'sem' and 'lavaan', both give p-values for the estimates but they use a Z test statistic.</p> | g66856 | [
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<p>I am not sure the subject enters into the CrossValidated interest. You'll tell me.</p>
<p>I have to study a graph (from the <a href="http://en.wikipedia.org/wiki/Graph_theory">graph theory</a>)
ie.
I have a certain number of dots that are connected.
I have a table with all the dots and the dots each one is dependa... | g46504 | [
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0.0... |
<p>I collected some data with an instruments with 1Hz sampling clock, now I want to low-pass filter the data to separate the mean and fluctuation part (Reynolds decomposition).
How can I design a low-pass filter with a cutoff period of 20 minutes?</p> | g66857 | [
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0.0064232246950268745,
0.02946791797876358,
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0.0036... |
<p>Some statistical tools offer methods of automatic identification of the distribution of data, such as the one <a href="http://blog.minitab.com/blog/adventures-in-statistics/how-to-identify-the-distribution-of-your-data-using-minitab" rel="nofollow">shown in this post</a>.</p>
<p>Generally, is this approach reliable... | g162 | [
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<p>I have intraday data (frequency = 1 min.) for 6 stocks and 1950 observations per each time series.</p>
<p>I checked stationarity for the level data and first difference and it appears that:</p>
<ol>
<li>5 stocks's level data are non-stationary and 1 is stationary,</li>
<li>all 6 stocks's first differences are stat... | g66858 | [
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0.04973400756716728,
0.06242028996348381,
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0.0291... |
<p>I am in need of variance of doubly truncated binomial distribution (equation number 3.69 on page number 137 of third edition of Johnson, Kemp and Kotz Discrete Probability Distributions).</p>
<p>Thanks.
Anwer</p> | g66859 | [
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<p>I am currently playing around with the MNIST dataset (<a href="http://yann.lecun.com/exdb/mnist/" rel="nofollow">http://yann.lecun.com/exdb/mnist/</a>) in R. The training set size is 60000x748 and it seems to drain all my memory even when constructing simple models like logistic regression.</p>
<p>My question is: h... | g66860 | [
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<p>For my research I conducted a creativity test and measured the quantity of ideas subjects had. Some people are extreme outliers as they have a lot of ideas or only 1 or 2 ideas. Intuitively I wanted to 5% trim my data to obtain a more robust estimation for my regression analyses. </p>
<ol>
<li><p>Is this justifyabl... | g66861 | [
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<p>I'll try to make an example to make it easier to understand the question.</p>
<pre><code>model{
constant1=(number)
constan2=(number)
for(j in 1:k){ #k defined in data
a[j] ~ dgamma(c[j],d[j])
b[j]~ dgamma(e[j], f[j])
c[j] ~ dgamma(constan1,constant2)
d[j] ~ dgamma(constan1,const... | g66862 | [
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0... |
<p>Could someone please refer me to papers that have imputed the mean to missing values of a continuous variable? (i.e. papers that have used mean imputation)</p>
<p>I have imputed my missing IMD values using the mean value and I want to see examples of other <strong>papers that have used mean imputation</strong> as w... | g27086 | [
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<p>I have sample counts of $n=20$ or $n=7$ taken from right-skewed and zero-inflated populations. The challenge in each case is to use the sample to estimate the total count in that population. Each of the populations are constituted of 300 such counts.</p>
<p>As the sample mean ($\times 300$) tends to be unrepresen... | g23451 | [
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<p>Is there a general principle on whether one should compute pearson correlation for two random variables X and Y before taking their log transform or after? Is there a procedure to test which is more appropriate? They yield similar but different values, since log transform is non-linear. Does it depend on whether X o... | g66863 | [
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... |
<p>The Pearson correlation coefficient of x and y is the same, whether you compute pearson(x, y) or pearson(y, x). This suggests that doing a linear regression of y given x or x given y should be the same, but I don't think that's the case. </p>
<p>Can someone shed light on when the relationship is not symmetric, and ... | g49431 | [
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<p>I have done a cross-sectional regression of time-series average returns on estimated Betas (over the same time horizon) to determine average premiums. So far so good. But I was told that the standard t-statistics can be biased, due to the fact that betas are estimated.</p>
<p>There is a solution by:</p>
<blockquot... | g66864 | [
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0.05... |
<p>I use <a href="http://hunch.net/~vw/" rel="nofollow">Vowpal Wabbit 7.3</a> for 10-class <a href="http://yann.lecun.com/exdb/mnist/" rel="nofollow">MNIST</a> classification, but can't get any reasonable results.</p>
<p>My usage of vw:</p>
<pre><code>./vw -d mnist_data/mnist.train --oaa 10 -f mnist_data/mnist.model
... | g66865 | [
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<p>I'm looking for textbooks that discuss penalized regression in a methodical manner and present various model selection methods, such as AIC, BIC, Cp as special cases of penalized regression. The textbooks i am looking for don't have to be dedicated to penalized regression, rather this subject can be discussed in a c... | g66866 | [
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<p>I am working on implementing a Logistic Regression model, using the newton-cg and lbfgs optimsers provided by scipy as the backend. I find the problems in which I fit the intercept, to be 50% slower than those in which I don't (which is equivalent to adding a column of ones on X).</p>
<p>I am guessing that the reas... | g26112 | [
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<p>I plotted a treatment effect on some performance measure over the course of an experiment. Stata has a nice feature called margins and marginsplot to do this.</p>
<p>So what I do is run a linear regression, where the time trend is a third degree polynomial, like</p>
<pre><code>reg depvar control##c.time1##c.time1#... | g26113 | [
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0.0265958... |
<p>Having used the NETLAB library for MATLAB to implement Bayesian Multi-Layer Perceptron (MLP) neural networks using MacKay's evidence framework, I am now experimenting with Markov Chain Monte Carlo (MCMC) methods using metrop() and hmc(). Does anyone have any advice for successful modelling using this approach (pref... | g66867 | [
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0.05933510884642601,
0.060... |
<p>I read somewhere, maybe incorrectly, that the Niederreiter quasi-random generator in MKL is 32 bit, and hence as a period of 2^32.</p>
<p>This is pretty low, is this correct?</p>
<p>This made me wonder if quasi-random number generator have such thing as a period.<br>
My understanding is that, the low discrepancy s... | g17830 | [
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<p>It seems to me as if the go-to technique that is used to make any prediction model more "interpretable" is to reduce the number of input variables that are used in the model. </p>
<p>I'm wondering if there are any <em>other</em> big picture approaches that one can take to make these models more interpretable? </p>
... | g46545 | [
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<p><a href="http://people.stfx.ca/tleo/ECON370Term2Lec4.pdf" rel="nofollow">This source</a> claims that measurement error in the dependent variable leads to more type I errors (page 2, 4th line of text).</p>
<p>However I thought that higher variance of residuals --> larger elements of diagonal of regressor variance co... | g46785 | [
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<p>I am attempting to find a reference which explains how one computes standard errors for local polynomial regression? Specifically, in R one can use the <code>loess</code> function to get a model object and then use the <code>predict</code> function to retrieve standard errors. Is there a reference somewhere to what... | g26119 | [
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<p>I am quite a newbie in this area: </p>
<ul>
<li>What are the boosting methods for regression systems? I know about <a href="http://en.wikipedia.org/wiki/Gradient_boosting" rel="nofollow">Gradient boosting</a>; are there any other approaches? </li>
<li>Are there textbooks or tutorials devoted to this area?</li>
</ul... | g46942 | [
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<p>I have been studying an incremental clustering algorithm for a large set of data that exhibit an inherent dynamic behavior (that is new data can get added over time and some older data may get deleted too based on the current situation). In this scenario, let us assume, some clusters are formed at one particular tim... | g66868 | [
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<p>i was wondering what is the differences between Mean Squared Error (MSE) and Mean Absolute Percentage Error (MAPE) in determining the accuracy of a forecast? Which one is better? Thanks</p> | g17237 | [
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<p>I'd like to do a power analysis for a single sample from binomial data, with $H_0: p = 0$, vs. $H_1: p = 0.001$, where $p$ is the proportion of successes in the population. If $0 < p <1$, I could use either the normal approximation to binomial, or $\chi^2$-test, but with $p =0$, these both fail. I'd love to kn... | g66869 | [
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<p>I have two variables, one containing project delivery rates for a particular language, and the second containing team size that worked on these projects. I am particularly new to statistics and I want to test the two variables which may or may not be dependent. In other words I want to test the dependency of these t... | g66870 | [
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... |
<p>I'm trying to create something similar to this.</p>
<p><img src="http://i.stack.imgur.com/QQVtd.png" alt="enter image description here"></p>
<p>So, 3 different Node classes, and a whole bunch of relationships between them. In my case, there should be roughly half of the number of nodes present at most.</p>
<p>Wha... | g21266 | [
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... |
<p>I want measure the value of a digital engagement, or a digitally engaged customer. Therefore I want to build a model to predict customer value as a function of digital engagement with a given digital asset such as my ipad app. Does anyone have thoughts on how to do this, or know of any literature that discusses appr... | g59 | [
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<p>How can I find out if the log-likelihood function has only one global maximum or if it has multiple local maxima?</p> | g66871 | [
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<p>Okay so I think I found a formula for the coefficient estimates but it is not very concise. It has like 6 sum of squares but it is in a single fraction so it is calculable. I was wondering what the simplest formula would be for estimating the coefficients for a linear regression. So say you had the regression equati... | g66872 | [
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0.0... |
<p>I am quite new to machine learning, CART-techniques and the like, and I hope my naivete isn't too obvious.</p>
<p><strong>How does Random Forest handle multi-level/hierarchical data structures (for example when cross-level interaction is of interest)?</strong></p>
<p>That is, data sets with units of analysis at se... | g66873 | [
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<p>I have received a sample, summarized by a frequency table with groups (i.e. 1-7, 7-10, 10-13, 13-16, etc...)</p>
<p>I calculated the mean and median, both were around 15, the mean was 15.3, the median 15.6. The mode was 18. I have calculated the mean by using the middle point of each interval. The median was calcul... | g66874 | [
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0.041980378329753876,
-0.001414610189385712... |
<p>My response variable is derived from a question in which respondents expressed a preference score (from 1 (do not like) to 10 (like alot)) for a range of scenarios.</p>
<p>I would like to analyse this data in relation to a number of socio-economic explanatory variables to find out what factors influence these pref... | g66875 | [
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0.00021530310914386064,
... |
<p>In short, I conducted a satisfaction survey in which surveyees are required to answer on a satisfaction scale from 1 to 7: 285 observations, 37 satisfaction variables.</p>
<p>Here is an example of what the scatterplot (jittered) between two variables from the data set looks like (I am working on R):</p>
<p><a href... | g66876 | [
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0.008387838490307331,
0.024171633645892143,... |
<p>I found a <a href="http://stats.stackexchange.com/questions/37833/minimal-number-of-points-for-a-linear-regression">similar question</a> in this forum. As a rule of thumb, since there are 4 independent variables in my case, I need 4*10=40 data points. However, my question differs slightly, since I want to ask about ... | g29474 | [
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0.00... |
<p>Kindly explain me how to estimate poisson regression model using iterative weighted least square method. I know it can be easily estimated in any software like Stata, SAS, SPSP etc but I want to estimate it manually. I am unable to understand the weight matrix (W) in the following iterative estimation equation:</p>
... | g66877 | [
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-0.014933724887669086,
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0.04005318880081177,
0.0017293815035372972,
... |
<p>More specifically, why do the likelihood ratio tests have asymptotically a $\chi^2$ distribution if the models are nested, but this is no longer the case for the not-nested models? I understand that this follows from the Wilks' theorem, but unfortunately, I don't understand <a href="http://www2.math.umd.edu/~slud//s... | g26141 | [
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0.04660416394472122,
0.04854350909590721,
0.0548... |
<p>I have overdispersed count data where the outcome is events (occurrence of a rare disease) and the covariate of interest is season. The unit of analysis is the number of events occurring in a country-season combination. We have 16 countries and 4 seasons repeated across each country, thus 64 data points:</p>
<p><im... | g26142 | [
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0.006975722964853048,
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... |
<p>Given $X$ is a continuous random variable whose density is symmetric about a point $a$.</p>
<p>Show that $V=X-a$ and $U=a-X$ have same distribution.</p>
<hr>
<p>$$F_U(u) = P(U \leq u) = P(X-a \leq u) = F_X(a+u)$$ and similarly $$F_W(w) = 1 - F_X(a-w) \longrightarrow f_U(w) = f_X(a+w) = f_X(a-w)$$ by symmetry. ... | g66878 | [
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0.03229067102074623,
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0.061207953840494156,
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-0.... |
<p>I am testing a neural net to predict numeric values. For that i am using a Training,Validation and Test split. I made a manual 4-Fold CV, this means i am getting 4 RMSE error, each one is the error of the i-th Fold on the test data.</p>
<p>How do i get global RMSE of all 4 Folds. Would it be (rmse_1 + rmse_2 + rms... | g66879 | [
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<p>Consider two different data time-series, <strong><em>Data1</em></strong> and <strong><em>Data2</em></strong>, expressed using <strong>inhomogeneous scales (units)</strong>. Each of these two data series is itself a weighted-average of a bunch of <strong>standardized</strong> individual series. </p>
<p>I would like... | g66880 | [
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... |
<p>When I studied Bayesian statistics, a question about the notation of Bayes' Theorem came to my mind. Below is the density function version of Bayes' Theorem, where $y$ is data vector and $\theta$ is the parameter vector:</p>
<p>$$
p(\theta|y)=\frac{p(y|\theta)p(\theta)}{p(y)}
$$
The numerator on the right handside ... | g66881 | [
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0.01098053902387619,
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<p>I am trying to choose the relevants parameters for a logistic regression with a huge number of parameters. I don't know the business signification of most of them, but I still have to optimize my system for better predictions. I am currently using the function stepAIC of the package MASS. This function is determinis... | g66882 | [
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0.059462618082761765,
0.033505313098430634,
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0.03019997663795948,
-0.03506774082779884,
0.04449215903878212,
0.07532326132059097,
0.060202... |
<p>If there is a population that we consider fixed (finite) with size N - say the customers at a bank at the end of a given month - and we want to conduct an experiment on this population by randomly sampling m for treatment 1 and k for treatment2 (where m+k <=N), how can you test the difference in proportions betwe... | g66883 | [
0.016202017664909363,
-0.03208046033978462,
0.0048461477272212505,
-0.04310421645641327,
0.032502681016922,
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0.009539102204144001,
0.029010623693466187,
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0.01037035696208477,
0.028059329837560654,
0.00858569610863924,
-0.005341122858226299,
0.02886... |
<p>I want to train a binary classification NN and part of this will require data pre-processing. However, I have a choice of which pre-processing algorithm to use. Of course I'd like to choose that one which is maximally informative for the purposes of training the NN. I feel sure that there might be some R package tha... | g66884 | [
0.035129208117723465,
-0.011485826224088669,
0.026248794049024582,
0.009743566624820232,
-0.0220504067838192,
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0.0033002838026732206,
0.03900650516152382,
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-0.041732411831617355,
-0.02576344832777977,
0.032927222549915314,
0.025756675750017166,
0.... |
<p>From the distribution density function we could identify a mean (=0) for Cauchy distribution just like the graph below shows. But why do we say Cauchy distribution has no mean?</p>
<p><img src="http://i.stack.imgur.com/zGTLU.png" alt="enter image description here"></p> | g26151 | [
0.013576352037489414,
0.03132675960659981,
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0.02518051490187645,
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0.07215099036693573,
0... |
<p>In my difference in differences model firms $> x$ belong to the treatment group whereas firms$< x$ act as control.</p>
<p>I have a two period model: </p>
<ul>
<li>In $t_1$ firm $i$ is $> x$ and thus belongs to the treatment group </li>
<li>In $t_2$ the same firm $i$ is $< x$ and belongs to the contr... | g66885 | [
0.002277266001328826,
-0.0041213990189135075,
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0.03623479604721069,
0.03340889513492584,
0.0055430117063224316,
0.017917348071932793,
0.0501021184027195,
-0.002995438873767853,
0.044382814317941666,
0.014745695516467094,
0.047144196927547455,
0.01557359378784895,
-0.0... |
<p>I have a model that produces data given a set of parameters. Now, given data, I'ld like to find out which parameters of the model are likely. I have an implementation in Matlab that uses Delayed Rejection Adaptive Metropolis for fitting (DRAM toolbox). Basically, DRAM samples parameter values, and tries to minimize ... | g66886 | [
0.039156705141067505,
-0.05805053189396858,
0.0033583317417651415,
-0.06150873750448227,
-0.06355404108762741,
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0.052608244121074677,
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-0.009406309574842453,
-0.04428786784410477,
0.009034596383571625,
0.07667170464992523,
0.... |
<p>For a time series I wanted to plot separately the partial auto correlation. Below is the graph for a time series which shows PACF plot of the time series $x$ which I wanted to reproduce: </p>
<p><img src="http://i.stack.imgur.com/T53D6.png" alt="acf_desired"></p>
<p>This shows plot of two time series of two time ... | g66887 | [
0.05883125588297844,
0.00565180042758584,
-0.012075464241206646,
-0.02368515357375145,
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-0.024812687188386917,
0.03444583714008331,
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-0.054535869508981705,
0.012725754640996456,
0.04449896886944771,
0.013828462921082973,
-0... |
<p>I have a database where each observation is a person. They were questioned on their attitude towards the consumption of X category of product. I have being using K-means to segment this data. </p>
<p>I have noticed that people under 19 years old tend to be quite different in their responses to those over 19. I was... | g46581 | [
-0.011088383384048939,
0.03136467561125755,
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0.005906150676310062,
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0.04246395826339722,
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0.10274945944547653,
... |
<p>the (symmetric) generalized secant hyperbolic distribution GSHD is very flexible but I found not much at all on how to estimate its 3 parameters. Given the location, I need to obtain scale & shape parameter. The generalized Gaussian (type 1) and the Student-t are similar, but the GGD1 is more peaky for the long ... | g12923 | [
0.008327379822731018,
0.003980609588325024,
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0.007950445637106895,
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0.04733481630682945,
0.028012672439217567,
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0.027201082557439804,
-0.01781589724123478,
0.001441781292669475,
0.013476356863975525,
0.014... |
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