question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I have an algorithm with 3 parameters and sum of these parameters is equal to one; $a_1+a_2+a_3=1$ and each of them must be between $0$ and $1$. I want to find the optimum point for this parameters. The equation is a linear combination of these three parameters, $y=a_1 g_1+a_2 g_2+a_3 g_3$ and $g_1$, $g_2$ and $g_3$... | g57837 | [
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<p>I am running a PLS model with a low number of observations ($n=50$). While several pieces of academic work argue that this sample size is appropriate to run this type of model, I am quite confused when it comes to the number of cases I take in my bootstrapping procedure.</p>
<p>I get some very strong path estimates... | g57838 | [
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<p>I am currently studying Treatment Effect Analysis and I am reading about the <strong>Conditional Independence Assumption (CIA)</strong>:
\begin{align}
(Y_1,Y_0)\perp D|X
\end{align}
So the outcomes are independent of the treatment, conditional on X.</p>
<p>First Question: Can someone explain this better? So give a ... | g400 | [
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<p>a referee asked me to "split" the significance level for the number of comparison, although i am not doing repeated comparisons but just spearman correlations between variables. I have set the significance level at p<0.05 but the referee is asking me to reduce it since the number of "correlations" is high. I wond... | g57839 | [
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<p>When reporting a two way 2 x 3 mixed ANOVA I have recently heard that the interaction effect should only be reported if the two main effects are significant (APA style). Is this correct? </p> | g41403 | [
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<p>I'm analyzing a set of data, and I like to fit a gamma distribution. I know how to do it in one dimension, but the data that I'm analyzing now are two dimensional. Is there any way that I can have a bivariate gamma function fitted into the data?</p> | g12632 | [
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<p>For example, we have a simultaneous equation model of supply and demand:</p>
<p>Supply: $$s(p)=\alpha_{s}+\beta_{s}p+\epsilon_{s}$$</p>
<p>Demand: $$d(p)=\alpha_{d}-\beta_{d}p+\epsilon_{d}$$</p>
<p>Market clearing condition: $$q = d(p) = s(p)$$</p>
<p>It is obvious that $E(\epsilon_{s}|p) \neq 0$ and $E(\epsilon... | g12634 | [
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<p>This is a Stata specific question, and may be better directed to Stata's own Statalist, but I'm trying here first. </p>
<p>Here is the situation. I have a multiply-imputed data set, where the number of imputations = 10 and where imputations are only performed on independent variables. I would like to run the <code>... | g12635 | [
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<p>I have a random forest being trained with <em>n</em> vectors each with <em>m</em> variables. Each variable has a cost based on how much time it takes to compute it (<em>m1</em> might take 1 unit while <em>m2</em> might take 100, making it more "expensive").</p>
<p>As far as I understand, random forests can give you... | g57840 | [
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<p>I don't understand why in the F test we calculate the ratio between MSE between subject and MSE within subject. As far as I know, this is due because we want to use the F distribution, which is a rate between two $\chi^2$ distribution divided their degree of freedom.</p>
<p>My question is: Why is not used a simple ... | g57841 | [
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<p>I have two variables:</p>
<p>1) Percentage of population of different geographic regions which has bought a certain category of product (say hair sprays) in the last MONTH</p>
<p>2) Percentage of population which has bought a specific brand of hair spray in the last YEAR.</p>
<p>I am trying to in which region the... | g12639 | [
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<p>Can anybody lead me with a small simulation? Should I calculate prediction error rate from a classification table while splitting the data into two parts then fitting on the training data and predicting on the test data and see the misclassification (i.e. how many 1 predicted as 0 and 0 as 1, calculating the rate of... | g57842 | [
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<p>I'm currently working on an adaptive learning system for high school maths. Students complete questions in quizzes and I need to be able to select questions of the appropriate difficulty level (say approximately 75% chance of being correct) and create a competency metric for measuring the skill of a student at a par... | g12641 | [
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<p>This is a practice question I came across when dong some goodness of fit test examples.A company sells cloths by mail order.The size of clothes is defined by hip size; thus the height of customers of a particular customer may vary considerably.<br>
Data set of heights sent in by customers of size 18 is given.Data se... | g57843 | [
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<p>What is the correct interpretation in (multiple) linear regression model when independent variables have different levels of significance? </p>
<p>For example, in the regression below the variable $X$ was significant at 0.001, but the intercept was significant just at 0.1. </p>
<p>I am not sure if I made myself ... | g57844 | [
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<p>Apologies if this is a simple question...</p>
<p>I am attempting to use the <code>errorest</code> function of the <code>ipred</code> package in R to to K-fold CV with GLM models of the binomial family, as well as earth (MARS) models. I have written routines to do CV and can run my GLM and other models through it a... | g57845 | [
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<p>I have two vectors of 100 real values each. I would like to use a permutation test for a few things such as the correlation of the two vectors. I would use the approach of keeping one vector stationary and then permuting the other in relation to it and then calculate the statistic of interest (such as correlation)... | g57846 | [
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<p>I am starting to look at particle filtering for a problem that I have. In particular, I would like to reduce the dimensionality of the particles.</p>
<p>The model that I have is able to be partitioned. Let my state vector be $\mathbf{x}=\begin{bmatrix}{\mathbf{x}_1}^T && {\mathbf{x}_2}^T \end{bmatrix}^T$.... | g12646 | [
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<p>So just "why" is $SE = \frac{s}{\sqrt n}$ ? How should one interpret/articulate the reason of having $\sqrt n$ in the denominator. Why do we divide sample mean by the square root of the sample size, intuitively speaking? And how/why is it called standard "error".
(Question equally applicable for true standard devia... | g57847 | [
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<p>Is it possible to apply the usual MLE procedure to the triangle distribution? - I am trying but I seem to be blocked at one step or another in the math by the way the distribution is defined. I am trying to use the fact that I know the number of samples above and below c (without knowing c): these 2 numbers are cn a... | g57848 | [
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<p><strong>The Situation:</strong> There are four <strong>*<em>identical</em>*</strong> spatial regression models, except each uses a different dependent variable. The independent variables consist of a standard set of variables derived from a principal component analysis. The dependent variables have been standardized... | g12648 | [
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<p>I have some sample data with age and I'd like to put them into bins (for example, ranges 20-24 25-30, etc.). The resulting variable would constitute values from 1-8. </p>
<p>What I'm confused about is what type of variable is the new variable?</p> | g12649 | [
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<p>I want to know what per cent is acceptable in a training survey? If we get scores of 77% satisfaction of our materials is that acceptable, good, poor?</p> | g37933 | [
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<blockquote>
<p>If two PDFs have the same moment generating function that converges in an open set around 0, then the PDFs are same.</p>
</blockquote>
<p>This is a well known fact, but I can't find its proof. If the PDFs are defined for only non-negative values, the MGF is essentially Lapleace transform and the uniq... | g12652 | [
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<p>I have searched high and low, and I simply cannot find this table anywhere. I am quite sure that for practical purposes I don't need it - that there are other methods, but it would be extremely useful if anybody could point me in the right direction of finding one online. Also, it needs to have negative values.</p... | g37704 | [
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<p>I know this is probably simplistic but what are Principal component scores?</p>
<p>This question originates from my attempt to understand this question <a href="http://stats.stackexchange.com/questions/213/what-is-the-best-way-to-identify-outliers-in-multivariate-data" rel="nofollow">here</a>.</p> | g33428 | [
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<p><img src="http://i.stack.imgur.com/HEZRS.jpg" alt="enter image description here"></p>
<ol>
<li><p>Assuming $H_0$ is true, what is the distribution of the test statistic?
t(29)</p></li>
<li><p>Assuming $H_0$ is true, what is the expected value of the test statistic? 87.70</p></li>
<li><p>The sample mean of 87.7 was ... | g41428 | [
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<p>I have temperature time series data that I have determined is not independently and identically distributed (from looking at the autocorrelation plots and Ljung-Box tests).</p>
<p>However, I am still able to fit PDFs, typically GEV, gamma, and Weibull distributions to my different data sets, with a $\chi^2$ goodnes... | g57849 | [
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<p>I have a set of samples with two labels red and black. I can build a logistic regression model to predict the label colour. Once a model is built, I would like to test whether it is overfitting or not.</p>
<p>Normally, I will set aside, say, 30% of my sample as out-of sample. Build a logistic regression model on th... | g57850 | [
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<h2>BOUNTY:</h2>
<p>The full bounty will be awarded to someone who provides a reference to any published paper which uses or mentions the estimator $\tilde{F}$ below.</p>
<h2>Motivation:</h2>
<p>This section is probably not important to you and I suspect it won't help you get the bounty, but since someone asked abou... | g12658 | [
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<p>Let's say you have an algorithm for minimizing the following loss function: </p>
<p>$$
loss = \sum_i l(y_i, f(x_i))
$$
Let's say you are in the binary classification case, and the ratio of negative to positive instances is $r$, where $r >> 1$ (say $r > 20$). </p>
<p>Given this algorithm and this setting,... | g57851 | [
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0.07553381472826004,
0.061... |
<p>I am trying to compare the observed number of DNA sequencing reads versus the expected number. There are loci where I would expect all the sequencing reads to be the same and there are other loci where I would expect them to be of 2 types, each one with an expected frequency. For example:</p>
<pre><code>LOCUS 1
OBS... | g57852 | [
0.015806149691343307,
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0.013882048428058624,
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0.06247817724943161,
0.06009828299283981,
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-0.011264125816524029,
0.024279475212097168,
-0.... |
<p>When $y = X\beta + e$, the least squares problem which imposes a spherical restriction $\delta$ on the value of $\beta$ can be written as
\begin{equation}
\begin{array}
&\operatorname{min}\ \| y - X\beta \|^2_2 \\
\operatorname{s.t.}\ \ \|\beta\|^2_2 \le \delta^2
\end{array}
\end{equation}
for an overdetermined... | g12660 | [
0.016466228291392326,
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0.036884065717458725,
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-0.020233329385519028,
-0.03842095658183098,
-0.06523281335830688,
0.07145936042070389,
0.010180451907217503,
... |
<blockquote>
<p>The national average price of a gallon of regular gasoline is 3.71
dollars. Linda would like to assess if the average gas price in her
city is significantly higher than the national average. She samples
gas prices at 20 local gas stations and records the price of a gallon
of regular gasoline... | g57853 | [
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0.0267508402466774,
0.04939592629671097,
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0.021183716133236885,
0.01... |
<p>My question might not be making much sense but I have been stuck for few days already so really do hope to achieve a solution on here.</p>
<p>So basically I have simulated a data set from a power-law distribution with a known parameter, I would like to test which method (binning methods+MLE) performs the best on es... | g57854 | [
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0.010679511353373528,
0.04915859177708626,
0.055968184024095535,
-... |
<p>I have implemented the non-negative matrix tri-factorization algorithm (<a href="http://aclweb.org/anthology//P/P09/P09-1028.pdf" rel="nofollow">link to paper</a>). If is similar to the more widely known NMF (non-negative matrix factorization), but incorporates <em>prior knowledge</em> to represent semi-supervised l... | g12662 | [
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0.011708831414580345,
0.0010624710703268647,
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... |
<p>On <a href="http://books.google.com/books?id=9St7DCbu9AUC&lpg=PA223&ots=MCCtt8-jIF&dq=Measurement%20Equivariance%20formal%20invariance&pg=PA161#v=onepage&q&f=false" rel="nofollow">page 161 of Lehmann and Casella's Theory of Point Estimation</a>, they introduce Functional Equivariance and Form... | g12665 | [
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0.09811907261610031,
0.01868603006005287,
0.045306529849767685,
0.0767047330737114,
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0.022876396775245667,
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0.024837175384163857,
0.007774375844746828,
0.0377... |
<p>I have a question about how to interpret some discrete data. Some are very easy, like the number of children in a household: that is a discrete and numerical, measured as a ratio variable.</p>
<p>Other variables are not that easy, for example</p>
<ul>
<li>age, measured in whole years: is that interval or ratio?</l... | g12667 | [
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0.014969252049922943,
0.027850894257426262,
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-0.05280281603336334,
0.026552921161055565,
-0.054938752204179764,
0.0676894560456276,
-0... |
<p>I have a set of data points distributed like a bell-shape curve with varying amplitudes and widths. I need to parameterize these data points and a Gaussian with amplitude, width and offset parameters function is just perfectly suited. </p>
<p>My y-values are defined between at 8 different points between [-2.3561 3... | g57855 | [
0.05008860304951668,
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0.005317105911672115,
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0.030945438891649246,
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0.001603156910277903,
-0.0014368065167218447,
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0.03110826015472412,
0.006917925551533699,
0.0... |
<p>I have one dependent variable and multiple predictors. Dependent is continuous and predictors may be continuous or dichotomous.</p>
<p>My sample is of 200 individuals. Each month, for 6 months, I have a measure of predictors for the 200 individuals and I would like to identify those which have a significant effect ... | g57856 | [
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0.010600593872368336,
0.015276175923645496,
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0.003045059973374009,
0.003843295853585005,
-0.011458950117230415,
... |
<p>I'm not big on statistics, so please excuse my ignorance.</p>
<p>I have a video recording that I want to evaluate, I have an algorithm that can transform this video into a time series where I have 0 everywhere except for a couple of frames where an event (A) occurs.</p>
<p>Then I have manual annotations of another... | g57857 | [
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-0.005989546421915293,
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0.019036656245589256,
0.023603368550539017,
0.0013... |
<p>I'm trying to derive the posterior distribution for the precision matrix for the multivariate normal with normal-wishart prior. According to wikipedia and other sources the answer is as follows:</p>
<p>$p(S|\mu, X, W, v) \\
\quad \sim W((W^{-1} + \sum_{i=1}^{N}(x_i-\bar{x})(x_i-\bar{x})^{T} + \frac{rN}{r+N}(\mu_0-\... | g12669 | [
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0.0005531841889023781,
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0.04651200771331787,
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0.02257891371846199,
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0.038995616137981415,
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... |
<p>I have several measurements of proportions (values in [0, 1]) $\theta_1,...,\theta_n$, each with an (asymmetric) 95% confidence interval. The $\theta$'s are repeated measurements of the same variable in the world and so I'd like to pool them together to get an estimate of $\hat{\theta}$ with its own confidence inter... | g12670 | [
0.04308661073446274,
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0.015081663616001606,
0.021192772313952446,
0.023578092455863953,
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0.013382536359131336,
-0.01259391475468874,
-0.0024773129262030125,
0.037660110741853714,
0.03... |
<p>The randomForest package in R software includes outlier function for the detection of outliers. This function uses proximity matrix or randomForest object for the outlier detection. The manual says that the type of the randomForest object can not be regression? Why is it so that this function can be used for classif... | g57858 | [
0.022148791700601578,
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0.012821939773857594,
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0.01402626559138298,
0.0031024173367768526,
0.02549886330962181,
0.018382320180535316,
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-0.06586912274360657,
0.024391934275627136,
0.06602481007575989,
0.01427094079554081,
-0.0013... |
<p>I have been adamantly searching the web to learn how to successfully implement a dynamic regression time series in the forecast package for R. The time series data that I am using is weekly data (frequency=52) of incoming call volume and prediction variables are mailers sent out every now and then. They are a signif... | g57859 | [
0.020710425451397896,
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0.002254707971587777,
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0.05434412136673927,
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-0.02019563876092434,
0.04450152441859245,
0.02967294119298458,
0.07325698435306549,
-0.00... |
<p>Is there a proof or theorem out there that says that the difference between the expectations of the order distributions of $n$ draws from a distribution $X$ decreases as the variance of $X$ decreases?</p>
<p>Specifically, I am asking:
If X and Y are probability distributions defined over the same range and with the... | g57860 | [
-0.0036940784193575382,
0.010147609747946262,
-0.038762789219617844,
-0.019590873271226883,
0.026920782402157784,
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-0.02780415117740631,
-0.020560840144753456,
-0.04330459237098694,
0.011023344472050667,
-0.030721299350261688... |
<p>I'm using Friedman's nonparametric tests for repeated measures for my thesis (I tried transformations on all variables first but data was still highly skewed) and had 2 questions:</p>
<ol>
<li><p>What are the best descriptive stats to put in a table. Means and SDs are commonly reported but Friedman's tests use rank... | g46474 | [
-0.01498515997081995,
-0.015622795559465885,
-0.01645652949810028,
-0.012220962904393673,
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-0.055343735963106155,
-0.004181173630058765,
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-0.046233925968408585,
0.020802438259124756,
0.022255176678299904,
0.006633251439779997,
0.03551643341779709,
... |
<p>I've been reading about generalised additive models. I've been using <a href="http://dl.dropbox.com/u/46726134/coris.csv">this data</a> (which is a reformatted version of data from <a href="http://www.stanford.edu/~hastie/Datasets/">Hastie's website</a>), and running my code in R. This data essentially consists of ... | g57861 | [
0.01349974237382412,
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-0.0225959662348032,
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0.0077846297062933445,
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0.01699984446167946,
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-0.07174921780824661,
-0.0021247812546789646,
0.05058138445019722,
0.028183961287140846,
0.0759662613272667,
-0.0... |
<p>Let $Y_{n}$ be a sequence of independent and identically distributed random variables and $X_{n}=\frac{Y_{n}}{n}$ . show that $X_{n}$ converges in probability. decide whether $X_{n}$ converges a.e or not.</p>
<p>thanks for help.</p> | g57862 | [
0.009372171945869923,
0.005314724985510111,
0.0037955469451844692,
0.021660808473825455,
0.025293715298175812,
-0.029124654829502106,
0.014162545092403889,
-0.01131760235875845,
-0.03881198167800903,
-0.009674911387264729,
-0.04285065829753876,
0.0018082456663250923,
-0.06689108908176422,
... |
<p>Why would one use age and age-squared as covariates in a genetic association study? I can understand the use of age if it has been identified as a significant covariate, but I am at a loss as to the use of age-squared?!</p>
<p>Thanks,</p>
<p>Kevin</p> | g57863 | [
0.022520797327160835,
0.018195178359746933,
0.01459779404103756,
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0.03262500837445259,
0.055530089884996414,
0.016497787088155746,
-0.0019230012549087405,
-0.0024569095112383366,
0.033653583377599716,
0.006567495875060558,
0.0554480217397213,
0.... |
<p>I'm using the <code>AIC()</code> function in R, where the argument <code>k</code> (default to 2) stands for the number of parameters. I'm not sure to understand well what does it mean.</p>
<p>How can you know k?</p>
<p>For example, in the case of $y=ax^2+bx+c$, does k equal 3?</p>
<p>As a sidenote, I saw that the... | g57864 | [
0.05054599046707153,
-0.013744564726948738,
-0.023003574460744858,
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0.055111028254032135,
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0.01801038347184658,
0.022387733682990074,
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0.07079596817493439,
-0.05829980596899986,
0.02796267531812191,
0.060299549251794815,
0.0... |
<p>Let's say I have two distributions I want to compare in detail, i.e. in a way that makes shape, scale and shift easily visible. One good way to do this is to plot a histogram for each distribution, put them on the same X scale, and stack one underneath the other. </p>
<p>When doing this, how should binning be don... | g57865 | [
0.04682062938809395,
0.04294921085238457,
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0.0012921758461743593,
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0.022173380479216576,
-0.048773143440485,
-0.03658447787165642,
0.024345623329281807,
0.008840481750667095,
0.07008855789899826,
0.0268... |
<p>From Kutner's Applied Linear Statistical Models</p>
<blockquote>
<p>The Bonferroni multiple comparison procedure does not lend itself to
data snooping, unless one can specify in advance the family of
inferences in which one may be interested and provided this family is
not large. </p>
<p>The Tukey and... | g12676 | [
0.0021878178231418133,
0.028958598151803017,
0.00014038512017577887,
-0.011852446012198925,
-0.0030005171429365873,
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0.08105289191007614,
0.029760992154479027,
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-0.04683464393019676,
0.023701833561062813,
-0.015645086765289307,
0.03118186630308628,
... |
<p>Hi I am unsure how to interpret the predicted probabilities for my logistic regression model. I am trying to work out if these variables effect the chances of becoming obese.
How would I interpret these results?</p>
<p>REGION<br>
Reference- East</p>
<p>-North 0.62</p>
<p>-South 0.54</p>
<p>-West 0.47</p>... | g49286 | [
-0.0033432927448302507,
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0.008144119754433632,
-0.008138849399983883,
0.028140267357230186,
0.015291097573935986,
0.0359601229429245,
0.03225930035114288,
-0.028455616906285286,
-0.051587242633104324,
0.01702624186873436,
0.022594572976231575,
0.07255172729492188,
0.0... |
<p>I am working on predictive model and when I evaluate it, I find good <code>accuracy_score</code>, <code>precision_score</code>, <code>recall_score</code>, and <code>f1_score</code>. But I don't get good results using confusion matrix. </p>
<p>What is the metric that should I Trust ?</p>
<pre><code>accuracy_score: ... | g57866 | [
-0.009919876232743263,
-0.011653905734419823,
0.0002668349479790777,
-0.0138400262221694,
0.07726992666721344,
-0.03757528215646744,
0.036316223442554474,
0.025896335020661354,
-0.04367902874946594,
-0.058280475437641144,
0.0251567754894495,
0.02244744263589382,
0.06724555790424347,
-0.071... |
<p>Please consider two data sets dat1 and dat2 in the following format.</p>
<pre><code>Dat1:
x1 x2 x3 x4 x5
1 3 8 2 10
2 12 2 9 6
</code></pre>
<p>and Dat2:</p>
<pre><code>var type
x1 discrete
x2 contns
x3 discrete
x4 discrete
x5 contns
</code></pre>
<p>I want to add t... | g41446 | [
-0.010297723114490509,
-0.02823903039097786,
-0.02112278714776039,
-0.0620235875248909,
0.0022818720899522305,
-0.009807293303310871,
-0.01896156184375286,
-0.04465167224407196,
-0.06308253854513168,
-0.05031825229525566,
0.011253508739173412,
0.021700359880924225,
0.01079228799790144,
0.0... |
<p>I'm reading an article, <a href="http://www.ncbi.nlm.nih.gov/pubmed/19925207" rel="nofollow">The commonality of neural networks for verbal and visual short-term memory</a> (Majerus et al., J Cogn Neurosci 2010 22(11): 2570), about brain imaging in which the results are analysed with multiple analyses.
One of them is... | g57867 | [
0.01649712212383747,
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0.001884156372398138,
-0.02009226381778717,
0.011936541646718979,
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0.04602241516113281,
0.018475772812962532,
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-0.028190404176712036,
-0.006368356291204691,
-0.022252224385738373,
0.07356221228837967,
0.03... |
<p>I have data which consist of three longitudinal series of financial data. The hypothesis is that two of the series are "caused" (in a loose sense) by the third. It is fine to investigate this as two separate hypotheses. All the series are about the relationship between two specific countries. There are data for ... | g12678 | [
0.0900578573346138,
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0.014548594132065773,
0.04537869617342949,
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-0.024853935465216637,
0.03465103358030319,
0.0031930101104080677,
0.0339503213763237,
0.0... |
<p>My textbook gives an example, that normal distribution family $\{N(0,\sigma^2):\sigma\in R^+\}$ is not <a href="http://en.wikipedia.org/wiki/Completeness_%28statistics%29" rel="nofollow">complete</a>, but a complete statistic, $T_n=\sum_{i=1}^n X_i^2$, can still be constructed from samples $(X_1,\cdots,X_n)$.</p>
<... | g57868 | [
-0.005153093487024307,
-0.0313483327627182,
-0.018523933365941048,
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0.039642032235860825,
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-0.015270817093551159,
-0.02596042864024639,
-0.03822227194905281,
0.025183560326695442,
... |
<p>Why $z=f(x)$ does not imply $E[z]=f(E[x])$ when f is not linear?</p>
<p>I can give an example, but I couldn't derive the general form.</p>
<p>Let $z = {x^2}$</p>
<p>Let $g(x)$ be the pdf of $x$. Then:</p>
<p>$ E\left[ z \right] = E\left[ {{x^2}} \right] = \int\limits_{ - \infty }^\infty {\left( {{x^2}} \right)g... | g57869 | [
0.008469808846712112,
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0.000991104869171977,
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0.04558908939361572,
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0.05558127537369728,
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0.006061256863176823,
-0.0019537718035280704,
-0.01687799021601677,
-0.010324635542929173,
0... |
<p>I understand from this question -
<a href="http://stats.stackexchange.com/questions/12900/when-is-r-squared-negative">When is R squared negative?</a></p>
<p>that the R squared value of a linear regression model can be negative if the intercept is constrained. And this makes sense if you define R squared as - </p>
... | g57870 | [
0.007103848736733198,
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0.02444053441286087,
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0.03618897497653961,
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-0.02594275213778019,
-0.014054626226425171,
0.06838204711675644,
0.05987211689352989,
-0.0308... |
<p>Let’s say we have data of some fruits and we want to consider different statistics for each fruit (there are various samples for each statistic). For example:</p>
<p>Watermelon:</p>
<ul>
<li>Sugar: 50, 57, 36… </li>
<li>Water: 101, 143, 128…</li>
<li>…</li>
</ul>
<p>Melon:</p>
<ul>
<li>Sugar: …</li>
<li>Water: …... | g12003 | [
0.036710966378450394,
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0.047911230474710464,
0.01676076650619507,
-0.0... |
<p>I have data where the dependent variable is discrete and lies between 20 and 40 (possible values are 20, 20.5, 21, 21.5, ..., 39, 39.5, 40). The variable measures some results from a game which can be between 20 (lowest achievable value) and 40 (highest).
After some hours of research on the web, I could not find a ... | g57871 | [
0.013420116156339645,
0.0006906008929945529,
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-0.041750963777303696,
... |
<p>I'm trying to perform a logistic regression with the dependent variable being whether a potential customer who attended an event purchased or did not purchase.</p>
<p>A subset of potential customers at the event participated in a meet-and-greet type activity with each other and existing customers. For each potenti... | g57872 | [
-0.03717847913503647,
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0.03990062698721886,
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0.0... |
<p>I'm working off my first independent project for some pattern classification. I'm utilizing some datasets from UCI machine learning, but am not sure on how to start with data normalization. The data isn't that large (feature vector around 15-20 dimensions), but I'm thinking there still needs to be some type of norma... | g27238 | [
0.028942884877324104,
0.01969371736049652,
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0.037033554166555405,
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0.01428981777280569,
0.0420844629406929,
0.017214644700288773,
0.00024... |
<p>With statistics: how would you explain the <a href="http://en.wikipedia.org/wiki/Sufficient_dimension_reduction" rel="nofollow">dimensionality reduction</a> and dimensionality addition? Like the conversion of a color picture to gray space so that a color blind person could more easily understand what was going on or... | g57873 | [
0.029803166165947914,
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0.04707... |
<p>In the stats class I took, all the results I have encountered about the convergence in distribution of some random variables are in one way or another consequences of the Central Limit Theorem.</p>
<p>Out of pure curiosity, I wonder whether there exists useful and commonly used results about the convergence in dist... | g57874 | [
0.04850148409605026,
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-... |
<p>I have a multiple linear regression problem $y=X\beta+\epsilon$. The number of observations $m$ is large, so by the time the data gets to me it's been summarized into:</p>
<ul>
<li>$m$</li>
<li>$X^TX$</li>
<li>$X^Ty$</li>
<li>$y^Ty$</li>
<li>$\sum_{i=1}^m{y_i}$</li>
</ul>
<p>The above list appears sufficient to co... | g12685 | [
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0.02498958818614483,
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0.001... |
<p>I am using hierarchical clustering to analyse time series data. My code is implemented using the <em>Mathematica</em> function <code>DirectAgglomerate[...]</code>, which generates hierarchical clusters given the following inputs:</p>
<ul>
<li>a distance matrix D</li>
<li>the name of the method used to determine int... | g41460 | [
0.03404613211750984,
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0.020195025950670242,
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0.001... |
<p>Hi
I am looking at extremely non linear data for which the ARMA/ARIMA models do not work well. Though, I see some autocorrelation, and I suspect to have better results for non linear autocorrelation.</p>
<p>1/ is there an equivalent of the PACF for rank correlation? (in R?)</p>
<p>2/ is there an equivalent of ARMA... | g41461 | [
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0.061028093099594116,
0.001498526195064187,
0.015031233429908752,
-0.0... |
<p>I guess this is similar to <a href="http://stats.stackexchange.com/questions/21658/is-it-necessary-for-a-sample-to-broadly-reflect-the-target-population-distributi">this one</a> but not quite the same. Consider I have a distribution that represents a population (e.g., Uniform(0,1)). I separate this interval (0,1) in... | g32468 | [
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0.02289898879826069,
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0.04044323042035103,
-... |
<p>When doing multivariate regression, it's often the case that some predictors often have many zero values - dichotomous inputs, dummy coding of polychotomous inputs, interval coding, etc. The fraction of nonzero observations for a predictor is especially decreased when interacting these variables.</p>
<p>It seems o... | g12687 | [
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0.031913675367832184,
... |
<p>Let X and Y be independent random variables such that $X∼Exp(1)$ and $Y∼Exp(2)$.
Find the probability that $3X+4Y≤5$.</p>
<p>I thought the equation for solving this was the integral from $\int_0^a \int_ 0^{(a-y)} \lambda e^{-\lambda x}*\lambda e^{-\lambda y} dx dy$ where $a = 5$, so I first started with the integr... | g57875 | [
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0.028852179646492004,
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<p>I learned that for an AR(1) model $x_n = b + \phi x_{n-1} + a_n$ with $|\phi| < 1$ and $a_n \sim WN(0, \sigma_a^2)$, the covariance between $x_n$ and $x_{n+h}$ is
$$
\mathrm{Cov} (h)
= \frac{\sigma_a^2 \phi^h}{1 - \phi^2}$$</p>
<p>Now I would like compute the variance of the sample mean
$$
\mathrm{Var}\frac{\su... | g57876 | [
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0.0015404053265228868... |
<p><img src="http://i.stack.imgur.com/e4SdT.jpg" alt="try to do linear regression"><img src="http://i.stack.imgur.com/kqEby.jpg" alt="enter image description here">My sample is 60 participants.
At first, I did not expect to analyze the correlation,
but the result is interesting,
so I would like to.</p>
<p>The 60 parti... | g57877 | [
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0.005247373133897781,
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0.05130022391676903,
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... |
<p>Recently, I used the methodology of response surface data mining proposed by Lee and Shin (2010) for job stress evaluation.
in their study they considered about 80 factors affecting job stress and their purpose is to select the significant factors.
in my study i considered 30 quality management practices and i studi... | g57878 | [
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0.025770733132958412,
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0.031611233949661255,
-... |
<p>I'm trying to do some modelling of time to event data and for various reasons, the Aalen additive model seems promising.</p>
<p>I'm using the <code>aareg</code> function in the <code>survival</code> package, but I'm struggling to find much literature (that isn't paywalled) to get more of a feel for the procedure.</... | g12689 | [
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0.06009500101208687,
0.044364385306835175,
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0.09390982240438461,
0.0... |
<p>"Distant supervision" is a learning scheme in which a classifier is learned given a weakly labeled training set (training data is labeled automatically based on heuristics / rules). I think that both supervised learning, and semi-supervised learning can include such "distant supervision" if their labeled data is he... | g57879 | [
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0.025099148973822594,
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0.07153013348579407,
0.000029451386581058614,
-0.05916539952158928,
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0.02442256733775139,
0.03589317202568054,
... |
<p>I am looking for alternatives to the kappa to assess inter-rater agreement. I've come across two hopefulls: Gwet’s AC1 statistic and PABAK. I wondered what the advantages and disadvantages of each were?</p> | g12691 | [
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0.01019512303173542,
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0.06337129324674606,
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0.000780926609877497,
0.... |
<p>I am simulating 10000 data-sets, each of length 20, that follow an autoregressive model with lag 1, using the following code:</p>
<pre><code>set.seed(1)
N = 20
n.reps <- 10000
burn.in = 50
total <- N + burn.in
x <- matrix(NA, n.reps, total)
x[ , 1] <- 0.1
noise <- rnorm(n.reps*total, 0, 0.1)
for(j ... | g57880 | [
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0.027201591059565544,
0.03092787228524685,
0.02... |
<p>I am a bit confused. Can someone explain to me how to calculate mutual information between two terms based on a term-document matrix with binary term occurrence as weights?</p>
<p>$$
\begin{matrix}
& 'Why' & 'How' & 'When' & 'Where' \\
Document1 & 1 & 1 & 1 & ... | g57881 | [
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0.009477776475250721,
0.0133902532979846,
0.022921230643987656,
0.03355494514107704,
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0.03733548894524574,
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0.021308748051524162,
-0.034108567982912064,
0.026678306981921196,
0.010677114129066467,
-0.006... |
<p>For tree based modeling most packages use some data element as the dependent variable. In uplift modeling the goal is to maximize the difference between treatment and control groups. </p>
<p>One way to implement this is with a CART which maximizes the t-statistic for an interaction term between the split (1 = left,... | g57882 | [
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0.0024937528651207685,
0.0399206206202507,
0.0035043011885136366,
0.04657218977808952,
0.0... |
<p>In the <a href="http://personality-project.org/r/html/omega.html" rel="nofollow">omega</a> function in the <a href="http://cran.r-project.org/web/packages/psych/index.html" rel="nofollow">psych</a> package for R, we have several outputs including Hierarchical omega, Asymptotic omega and Total omega. </p>
<p>I was r... | g12695 | [
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0.012825043871998787,
0.0561184324324131,
0.0... |
<p>Is it okay to feed $I(0)$ variables into the Johansen procedure? I've read three sources that seem to state that this is not what you're supposed to do. However, whenever I've done this, I notice that $\Pi$ is full rank and so it leads me to a VAR and therefore I don't see any problem with this. </p> | g403 | [
0.04909104108810425,
0.000005896441507502459,
0.022197067737579346,
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0.024201108142733574,
0.009377568028867245,
0.0023769522085785866,
-0.0147491591051220... |
<p>I've got 36 months of timeseries data, and eyeballing it, it has a linear trend upward. I wanted to do a little more than just eyeball it though. So I put together a correlogram of autocorrelation values for lags 1 to 12 on my observations. They're all positive. Would you say that's good evidence that I've got a lin... | g41475 | [
0.05028160288929939,
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0.060614511370658875,
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0.03850225731730461,
0.06749260425567627,
0.04589381068944931,
-0... |
<p>If I have 1 independent variable (continues) and 1 dependent variable (binary), I can conduct logistic regression and ROC analysis, and I can get a cut-off point of independent variable using ROC analysis.</p>
<p>But, If I have 2 independent variable, how can I get two cut-off point in multivariate ROC analysis. </... | g57883 | [
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0.030297257006168365,
0.002637632889673114,
-... |
<p>I have a dataset with 1747 observations. Outcome variable is categorical, while independent variables are continuous, so I decided to use logistic regression for my analysis. I built the model using backward elimination algorithm, and resulting model seemed to be quite stable. Checking VIF values provided very good ... | g57884 | [
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0.009203012101352215,
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0.021225756034255028,
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0.038583751767873764,
0... |
<p>Normally you have a beta distribution with shape parameters $a$ and $b$.
The mean of this distribution is $a / (a + b)$ and the sample size, or the confidence (or K) is $a + b$.</p>
<p>Now, if you do some trials, with let's say N positive outcomes and M negative outcomes, you end up with a posterior distribution th... | g41476 | [
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0.04743301495909691,
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0.... |
<p>I'd like to ask if someone could help me with the following problem:</p>
<p>we have measured the same sample 5 times and we would like to check if there are significant differences in mean and stdev values if we use:</p>
<ul>
<li>All 5 datapoints</li>
<li>Only the last 4 datapoints</li>
<li>Only the last 3 datapoi... | g250 | [
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0.0331149585545063,
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0.0... |
<p>I've read that for the Maximal Margin Classifier SVM, after solving the dual problem, most of the lagrange multipliers turn out to be zeros. Only the ones corresponding to the support vectors turn out to be positive.</p>
<p>Why is that?</p> | g57885 | [
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0.02675769478082657,
0.10189255326986313,
... |
<p>This is a homework question so I would appreciate hints. I believe I have the first part correct, but I fail to see how the second part is different.</p>
<p>Assume square error loss, $L(\theta ,a)=(\theta - a)^2$.</p>
<ol>
<li>When $X|\theta \sim N(\theta , \sigma^2)$, show $\delta (X) = c$, where $c$ is a consta... | g49734 | [
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0.02567302994430065,
0.... |
<p>I'm having trouble distinguishing between the concepts of scedasticity and stationarity. As I understand them, heteroscedasticity is differing variabilities in sub-populations and non-stationarity is a changing mean/variance over time. </p>
<p>If this is a correct (albeit simplistic) understanding, is non-stationar... | g12702 | [
0.028709739446640015,
-0.0015869245398789644,
-0.011637724004685879,
-0.008729929104447365,
0.04202233627438545,
-0.007737920619547367,
0.022629866376519203,
0.011200763285160065,
-0.0009866345208138227,
0.007871224544942379,
0.03353918343782425,
0.0028579337522387505,
0.009297587908804417,
... |
<p>One of the problems in my textbook is posed as follows. A two-dimensional stochastic continuous vector has the following density function:</p>
<p>$$
f_{X,Y}(x,y)=
\begin{cases}
15xy^2 & \text{if 0 < x < 1 and 0 < y < x}\\
0 & \text{otherwise}\\
\end{cases}
$$</p>
<p>Show that the marginal densi... | g57886 | [
0.05836813151836395,
-0.014859269373118877,
-0.019914284348487854,
-0.030444560572504997,
-0.018666863441467285,
0.006494279019534588,
0.027258139103651047,
-0.027154048904776573,
-0.08546586334705353,
-0.016441218554973602,
0.0017221003072336316,
0.03194529935717583,
0.045744746923446655,
... |
<p>I am using <code>LibSVM</code> classifier in my Java code and I am getting correct results as I verified that with weka GUI, however, when I want to get the weights of the support vectors, I get an empty string. This is a snapshot of my code:</p>
<pre><code>LibSVM svm = new LibSVM();
svm.buildClassifier(train_data)... | g57887 | [
0.006691809743642807,
-0.007193343713879585,
0.006536317523568869,
-0.06738726049661636,
0.038887664675712585,
0.01916664093732834,
-0.0013195124920457602,
0.016403593122959137,
-0.05764198303222656,
-0.035196904093027115,
-0.03584088385105133,
0.004354202654212713,
0.0273506511002779,
0.0... |
<p>I have a large survey data set, about 15 years of data. One binary variable (yes/no) in which I'm interested was over-estimated due to a data collection error for about 1 1/2 years. I'm not sure how to handle these data. Could it treated as missing data? Seems like MNAR in that case. If so, and all the other mi... | g57888 | [
0.0398491695523262,
-0.07080026715993881,
0.015511048957705498,
-0.04869476705789566,
-0.057679433375597,
0.04581407457590103,
-0.021873369812965393,
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-0.022122254595160484,
0.0001442267675884068,
0.022974640130996704,
-0.007202292326837778,
-0.002454271074384451,
0.... |
<p>I am unsure what I should do if I have two Normally Distributed variables with known parameters and I want to find the probability that one of these variables is greater than the other. Should I use the distribution of differences of the two normal variables, as is shown <a href="http://mathworld.wolfram.com/NormalD... | g27245 | [
0.0861857607960701,
-0.02453714609146118,
-0.010181277990341187,
-0.014474851079285145,
-0.001279986696317792,
0.011854239739477634,
0.0071844677440822124,
0.02572512812912464,
-0.04165401682257652,
-0.0022858770098537207,
0.009537138976156712,
-0.02971351146697998,
0.0009361210977658629,
... |
<p>I have a number of plants and all of them undergo a 'treatment'. Then I measure the amount of plants that react to the treatment and the amount that do not. Is there a way to calculate a test statistic (to test for the significant effect of treatment)? If yes, is there a way to infer an effect size measure?</p>
<p>... | g57889 | [
0.00567415077239275,
0.017339594662189484,
0.0002335847821086645,
-0.031405240297317505,
-0.028500936925411224,
-0.07212511450052261,
0.039340827614068985,
0.059215299785137177,
-0.024523768573999405,
-0.01531139574944973,
-0.006567379459738731,
0.029408005997538567,
0.02938375249505043,
0... |
<p>Suppose a population of dentists are sent an inquiry. A number of inquiries are filled in and sent back. Each question on the inquiry represents a certain number of points. The total number of points represents the precentage that a dentist adheres to some safety regulation. I would like to test whether there is som... | g12708 | [
0.03584669530391693,
0.012222629971802235,
-0.016507059335708618,
-0.03864886239171028,
-0.014051624573767185,
-0.024033570662140846,
0.07575441896915436,
-0.02513471245765686,
0.035773999989032745,
0.0010463707149028778,
0.022118380293250084,
0.008529515005648136,
0.0009272044990211725,
0... |
<p>I'm trying to generate correlated data (preferably multinormal) with predefined correlations (e.g. 0.35 or 0.9). Any idea how I can do it? I'm using R and I did find a way to generate this (using mvrnorm), but you need to supply a covariance matrix. I have a covariance matrix with correlations around 0.9; however, I... | g12709 | [
0.026497140526771545,
-0.05949034541845322,
0.01474726665765047,
-0.05017488822340965,
-0.018904225900769234,
0.005519022233784199,
-0.013386916369199753,
-0.0013322997838258743,
-0.02397899515926838,
-0.03620848059654236,
-0.0260009802877903,
-0.01600535772740841,
-0.0040961806662380695,
... |
<p>I want to know if changing a button color has a positive effect on different measures (see the 4 measures below), using the following process:</p>
<ul>
<li>There's a default button, which is the fixed control group with no changes. This means I'm interested in one-tailed p-values for pair-wise comparisons.</li>
<li... | g57890 | [
-0.009268534369766712,
-0.02287297137081623,
-0.009583418257534504,
-0.028851838782429695,
0.020043913275003433,
-0.07348940521478653,
0.03631511330604553,
0.01880747824907303,
0.01321416161954403,
0.013685920275747776,
-0.0018470078939571977,
0.01792394183576107,
-0.011309060268104076,
0.... |
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