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# Stats Stack Exchange

I have a question about Boosting and stacking in machine learning. Suppose that I will train neural network, SVM and logistic regression using optimization algorithm to optimize best inputs in first phase. So now I have 3 trained models with different...
From: Stats Stack Exchange | By: user2991243 | Saturday, February 28, 2015
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Let's say you are doing linear regression. We are trying to fit $w^Tx=y$. One way to do that is by utilizing gradient descent to minimize this function: $J(w) = \frac1{2n} \sum_{i=1}^{n} (w^Tx-y)^2$. (Context: slight variation from Andrew Ng's Coursera...
From: Stats Stack Exchange | By: eternalmothra | Friday, February 27, 2015
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In a food processing plant, on average, 2 packaging machines breakdown per week. I let x be the number of processing machine breakdowns in a week. So x is Poisson(2), but one part of the question says: in a random sample of 26 machines what is the probability...
From: Stats Stack Exchange | By: Drewiske | Saturday, February 28, 2015
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In high energy physics I know it is common task to find the best separation point between two classes of binned data, usually signal and noise. This separation point is determined by making a decision based on maximizing the amount of signal while minimizing...
From: Stats Stack Exchange | By: Andre5 | Saturday, February 28, 2015
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I am struggling with the following exercise and hope that someone can explain me how to derive the solution: Let $\Omega =${a,b,c} with $\mathbb{Q}$({a}) = 1/2, $\mathbb{Q}$({b}) = 1/4 and $\mathbb{Q}$({c}) = 1/4 and X a random variable defined by...
From: Stats Stack Exchange | By: jeffrey | Saturday, February 28, 2015
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In fact, I have two questions: 1- do we need to check for the multicollinearity when we deal with linear discrimination analysis? 2- how to solve those variables which are multi-collinear? Lets say I want to perform Linear Discrimination Analysis and...
From: Stats Stack Exchange | By: Nemo | Saturday, February 28, 2015
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I'm designing an experiment, in which 40 participants answer 10 questions, 5 in condition $A$ and 5 in condition $B$, and I'm interested in the difference between the two conditions. It's not clear to me what's the best way to allocate questions to each...
From: Stats Stack Exchange | By: Eoin | Saturday, February 28, 2015
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I am a self-taught person and I would like your help. I am learning about predictive modeling in general, and I'm also trying to do predictive modeling for a specific problem. I am exploring alternative ensemble learning algorithms (CART, Random Forest)....
From: Stats Stack Exchange | By: user3378649 | Saturday, February 28, 2015
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To analyse the Box-Cox plot in a mixed effect model, no simple transformation/ code in R exists. So which of the following approaches would be valid ways and why? 1) Take a random sample (say of size n) from the data set, then consider the box plots...
From: Stats Stack Exchange | By: a.e. | Saturday, February 28, 2015
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Suppose we have n+1 random variables i.i.d. distributed $X_0,X_1,...X_{n}$. Is it the same operation if I generate n samples according to $X_0$ $\{S^0_1,S^0_2..,S^0_n\}$, or if I take from each of the random variables $X_1,...,X_{n}$ a sample, thus $\{S^1_1,S^2_1..,S^n_1\}$....
From: Stats Stack Exchange | By: omar | Saturday, February 28, 2015
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I'm trying to build a training set for a classifier. A vector evaluates to either conclusive 'C' or unconclusive 'U'. U Y69S 12 -1.5 1.83 3.45 5.412 6.441 9.864 14.666 15.68 12.082 8.384 4.016 0.0 U Y69T 12 0.904 1.699 3.672 6.543 7.642 10.435 16.099...
From: Stats Stack Exchange | By: TMOTTM | Friday, February 27, 2015
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I often need to work with and analyse electronic medical record data which cannot be moved from the servers in the organisation where it resides, due to ethical reasons. Is anyone aware of a method or approach that could create a copy/simulation of the...
From: Stats Stack Exchange | By: AndyC | Saturday, February 28, 2015
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Is there any R package implementing optimal brain damage algorithm or anything similar what can be used to prune neural networks models?
From: Stats Stack Exchange | By: Tomas Greif | Saturday, February 28, 2015
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I am looking to validate a questionnaire and would like to know if I can use factor analysis on the multiple-choice questions (MCQ). Also, I have another section where I am asking about participants attitude on a Likert scale of 1-5. Can I apply factor...
From: Stats Stack Exchange | By: resp78 | Saturday, February 28, 2015
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The data stem from a 2x2-factorial design where both factors have two levels. The x-axis shows the words of a sentence and the y-axis the mean reaction time for each single word. Here is how I visualize the data so far with base R: I find the usual method...
From: Stats Stack Exchange | By: brauner | Saturday, February 28, 2015
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Let $Y$ ~ $MVN_3(\mu, \Sigma)$ where $\mu = (5,6,7)$ and $\Sigma = \begin{bmatrix}2 & 0 & 1\\0 & 3 & 2\\1&2&4\end{bmatrix}$ Find (a) The marginal distribution of $Y_1$ (b) The joint distribution of $Y_3$ and $Y_1$ (c) The conditional...
From: Stats Stack Exchange | By: Patrick Kriebel | Saturday, February 28, 2015
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Hypothetical situation that I'm trying to use for understanding some criminal statistics. Let's say there is a city with 10 banks. One criminal robs two banks before being arrested and placed in jail. Would the probability of having a bank robbed be...
From: Stats Stack Exchange | By: Twitch | Friday, February 27, 2015
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I expect there may be no definitive answer to this question. But I have used a number of machine Learning algorithms in the past and am trying to learn about Bayesian Networks. I would like to understand under what circumstance, or for what types of...
From: Stats Stack Exchange | By: AndyC | Saturday, February 28, 2015
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if I am using a good uniform pseudo random number generator to inject real values between 0 --> 1, how often should a 0 or 1 be returned? So for example, if I inject 10 million random uniform numbers in the range of 0 --> 1, should I expect to...
From: Stats Stack Exchange | By: Jonjilla | Saturday, February 28, 2015
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i know some basic things about linear classifiers. i prefer two think geometrically about them. and what'll happening if covariance Matrix were different things. Generally; What's the difference of these Two Algorithm?
From: Stats Stack Exchange | By: Bidgoli | Saturday, February 28, 2015
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Circular symmetric complex Gaussian zero mean PDF is defined as : $$f(z)= \frac{1}{\pi^N||M||} e^{-z^*M^{-1}z}$$ where $M$ is hermitian semi positive definite, $z \in \mathbb{C}^{N \times 1}$ and $||\cdot||$ is determinant operation. Question If we...
From: Stats Stack Exchange | By: kaka | Saturday, February 28, 2015
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How do you interpret and report partial eta-squared in a two-way anova? I have run a two-way anova to inspect whether gender and level of education interact to have an effect on positive affect. Together, they do. Partial eta-squared = 0.67. What does...
From: Stats Stack Exchange | By: PocketPsychology | Saturday, February 28, 2015
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I understand where the E step happens in the algorithm (as explicated in the math section below). In my mind, the key ingenuity of the algorithm is the use of the Jensen's inequality to create a lower bound to the log likelihood. In that sense, taking...
From: Stats Stack Exchange | By: Heisenberg | Saturday, February 28, 2015
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it looks like noise variance does not need to be estimated if the noise is an iid, but on the other hand variance is constant if it is an iid? is white noise an iid? Please clarify.
From: Stats Stack Exchange | By: user70030 | Saturday, February 28, 2015
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I would like to detect changes in time series data, which usually has the same shape. So far I've worked with the changepoint package for R and the cpt.mean(), cpt.var() and cpt.meanvar() functions. cpt.mean() with the PELT method works well when the...
From: Stats Stack Exchange | By: mlee | Friday, February 27, 2015
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I have some 1D data that I want to cluster using Mixture of Gaussian. However, the data "wraps around" at two extremes. Specifically, I have a list of angles from $-\pi$ to $\pi$ and the data near two ends should actually be close to each other. Thus,...
From: Stats Stack Exchange | By: zyl1024 | Saturday, February 28, 2015
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Here is my inference problem: $M \rightarrow \theta \rightarrow D$. In this case I observe $D$ and I would like to optimize the parameters for $M$ (the physical model). But $M$ does not directly inform on $D$ because there are "uncertainty" parameters...
From: Stats Stack Exchange | By: simurg | Saturday, February 28, 2015
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Assume you have a general linear Model #1 based on observed data with residuals: $$Model 1: y_i = \beta_0 + \beta_1 x_{1i} + \beta_2 x_{2i} ... + R_i$$ Assume that with future data from new variables we can make a statistically better general linear...
From: Stats Stack Exchange | By: jtd | Friday, February 27, 2015
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I am trying to design a numerical scale which would describe the severity of a certain disease (in this particular case anaphylaxis). I have a set of clinical symptoms and a database of patients who had anaphylaxis and had their symptoms described. I...
From: Stats Stack Exchange | By: WojciechF | Friday, February 27, 2015
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I want to write a function for the following table Group1 Group2 Age diffG1 diffG2 A K 12 1.33 1 A K 14 1.33 1 A K 16 1.33 1 B M 12 -1.166 -1 B M 11 -1.166 -1 C M 12 -0.16 -1 C M 13 -0.16 -1...
From: Stats Stack Exchange | By: user3546966 | Friday, February 27, 2015
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Say I have a model: ln y = B0 + B1(x1) + B2 ln(x2) + u and the B2 estimate I get is 0.5 If I change the model to be ln y = B0 + B1(x1) + B2 ln(x2^2) + u the estimate will change to 0.25, but why is this the case? Thanks in advance for any help! Best...
From: Stats Stack Exchange | By: Jona | Friday, February 27, 2015
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I have two sets of observations (1 and 2) of the same element, but the methods of measurements were different (say for obs#1 method A and for obs#2 method B was implemented). A subset of samples measured using method A is also measured using method B,...
From: Stats Stack Exchange | By: ToNoY | Friday, February 27, 2015
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Background: I want to compare two devices measuring a certain characteristic on a subject. Thereto, each subject is measured once with device A and once with device B. It needs to be assumed that every subject has a different expect value. A reasonable...
From: Stats Stack Exchange | By: Nussig | Friday, February 27, 2015
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A 95% confidence interval under Neyton-Pearson is defined as the interval upon which if we took many samples of size n from the population, 95% of the intervals formed around the sample means would contain the population mean. In the circumstance where...
From: Stats Stack Exchange | By: NickB2014 | Friday, February 27, 2015
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The Wiener process at time $t=0$ is $0$. It has independent increments, so $W_t-W_0 \sim N(0,t-0)$, but wouldn't it mean that $W_t\sim N(0,t)$ for every $t$? But if I try to simulate a a Wiener-process in excel, it won't look like a Wiener process at...
From: Stats Stack Exchange | By: FelB | Friday, February 27, 2015
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I have to compare two large samples ($N = 10^{6}$) of discrete data drawn from power-law distributions to assess whether they are significantly different. I can't do that by means of Kolmogorov-Smirnov test because my data are discrete, thus I was wondering...
From: Stats Stack Exchange | By: stochazesthai | Friday, February 27, 2015
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In part of an econometric project I need to run a specific DiD. Yet I can't find specific literature related to it. I'm sure it exists similar things but I have difficulties. Maybe you could help me :) So, to explain briefly. I have a reform that has...
From: Stats Stack Exchange | By: Dada | Friday, February 27, 2015
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I applied two unsupervised algorithms to the same data, and would like to make a confusion matrix out of results, how should I achieve it in R? An example with R codes like following: xx.1 <- c(41, 0, 4, 0, 0, 0, 0, 0, 0, 7, 0, 11, 8, 0, 0, 0, 0,...
From: Stats Stack Exchange | By: hiberbear | Friday, February 27, 2015
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I am not entirely sure what I should be googling for this in my present context. Basically I am working with a set of latent variable models such as the Gaussian Processes latent variable model (GPLVM). Where, as the name suggests, you find a latent...
From: Stats Stack Exchange | By: Astrid | Friday, February 27, 2015
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In a Gaussian Process (GP), we know that choice of the covariance function determines the shape of function that can be drawn from the GP. eg. Constant : $\sigma _{o}^{2}$ Draws constant function based on the hyper parameter $\sigma_{o}$ Linear kernel...
From: Stats Stack Exchange | By: Ankit Chiplunkar | Friday, February 27, 2015
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Say you have an independent variable, $x$, and two dependent variables $y_1$ and $y_2$. I want to calculate whether these two variables have a significantly different slope. I can do it by calculating separate regressions, and then using he method mentioned...
From: Stats Stack Exchange | By: naught101 | Friday, February 27, 2015
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I have a set of data described by $n$ features. I do a principal component analysis (PCA) to reduce it to just 2 dimensions so I can make a 2D plot of the data, with the first two Principal Components. I'd like to know if there is a way to know what...
From: Stats Stack Exchange | By: luke88 | Friday, February 27, 2015
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I have been looking for a good reference where I can find how technical indicators of stock market analysis are calculated. I have a dataset (time series) which I want to extract these indicators to apply into another program but I can't find a good...
From: Stats Stack Exchange | By: Felipe Oriani | Friday, February 27, 2015
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I know that LDA is used for classification and MLR is for regression. Lets say I have a matrix X (independent variables) and Y(dependent variables) if the Y is continues and I make a regression , it becomes MLR if the Y is categories (like 1111122222)...
From: Stats Stack Exchange | By: Nemo | Friday, February 27, 2015
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My question is that Only MLR can be built when the number of variables are lower than the number of samples? one says because the regression coefficient (based on least squares ) can be calculated Can one explain why is it like this ?...
From: Stats Stack Exchange | By: Nemo | Friday, February 27, 2015
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For the covariance function covSEiso: $$k(x^i,x^j)=\sigma_f^2\exp(-(x^i-x^j)^T{\rm diag}(l)^{-2}(x^i-x^j))+\sigma_n^2\delta_{ij}$$ in GPML Matlab package, there are three types of hyper parameters, $(\sigma_f, l, \sigma_n)$. The code seems to optimize...
From: Stats Stack Exchange | By: Jinkyoo Park | Thursday, February 26, 2015
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When using fractional polynomial models it has been suggested to use the first derivative of the polynomial function to identify significant periods of change and the second derivative to identify significant turning points. If a fractional polynomial...
From: Stats Stack Exchange | By: StevenP | Friday, February 27, 2015
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I want to code the following formula in R. I will be more happy if any one provides me some help. The formula is Eti = Eo + (Em-Eo/tm-to)*(ti-to) I will be gladfull for thsi help
From: Stats Stack Exchange | By: Karanar | Friday, February 27, 2015
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I am trying to find the best model to solve the following problem: I have various players in a network. I have to visit all these players in the network. The players are visited in an optimal route, and to visit all the players I have costs (km and hours)....
From: Stats Stack Exchange | By: Bilell | Friday, February 27, 2015
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I have a set of lines. I measure their length each 5 times, and then take the mean of their lengths (as I measure them). I also take the standard deviation. I want to know the 'average' line length. Certainly I can take the mean of the mean line lengths...
From: Stats Stack Exchange | By: chrisb2244 | Friday, February 27, 2015
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