question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p><em><strong>Introduction</em></strong>:</p>
<p>I'm working with heart rate data. IBI (InterBeat Interval) is defined as the time period between any two consecutive heart beat and is usually measured in millisecond. I have followed a subject for 6 days and using a device, I have all his IBI measures. My dataset has ... | 70,122 |
<p>I am exploring the flexibility of partitional clustering algorithms. In particular, I would like to introduce more general distances than the ones which are used by default. </p>
<p>Let us consider, for simplicity, <code>dbscan</code> contained in the R-package <code>fpc</code>. It allows the user to specify a "dat... | 70,123 |
<p>I have this confusion related to interpreting the precision matrix. Suppose I have four variables forming a multivariate gaussian distribution with the following precision matrix</p>
<pre><code>Q = 1 -1 0 0
-1 2 -1 0
0 -1 2 -1
0 0 -1 1
</code></pre>
<p>If I invert this precision matrix an... | 70,124 |
<p>I am using a <a href="http://en.wikipedia.org/wiki/Relevance_vector_machine" rel="nofollow">relevance vector machine</a> in R, <a href="http://rss.acs.unt.edu/Rdoc/library/kernlab/html/rvm.html" rel="nofollow">rvm()</a>, to solve a regression problem. I need to know the variance of the fitted values for each identif... | 30,880 |
<p>In general, how is the required sample size derived for a specific power and a specific significance in a test rule?</p>
<ol>
<li><p>Since the alternative hypothesis may not be simple and the power is a function of the sample's distribution, what does the specific power require? Is it the minimum power over the sam... | 70,125 |
<p>I have a problem when performing a Hausman test.</p>
<p>I have a panel dataset that has five panels. I am estimating the same model twice, once using quarterly and another using half-year data.</p>
<p>My dependent variable and some of my explanatory variables contain time-series data, which changes across individ... | 30,881 |
<p>First, let me acknowledge up front that I'm not as well versed in statistics and mathematics as I'd like to be. Some might say have just enough knowledge to be dangerous. :D I apologize if I'm not using terminology correctly.</p>
<p>I am trying to model the probabilities of a system transitioning from one state t... | 70,126 |
<p>Hi I m working on a unsupervised problem to partition my dataset.
I have access to the class labels for this dataset.
Now I am trying to use Jaccard coefficient to compute correlation between cluster and class matrices of my data to perform cluster validation.
I have two questions:
a) Is Jaccard coefficient (JC) bet... | 70,127 |
<p>I have a dataset, on which I am doing some data mining. My mining method has certain parameters which I can fiddle with, presumably leading to better or worse quality results. I measure the quality of these results with some statistical tests, which gives me a low P-value for "good" results.</p>
<p>This generates a... | 70,128 |
<p><a href="http://en.wikipedia.org/wiki/Cyclostationary_process" rel="nofollow">http://en.wikipedia.org/wiki/Cyclostationary_process</a></p>
<p>What are the methods in modelling and forecasting such time series?</p>
<p>It is mentioned in the link above that there is a deterministic approach to treat such a time seri... | 30,885 |
<p>Is there a limit which is the least acceptable when using multiple imputation (MI)?</p>
<p>For example can I use MI if the missing values in a variable are the 20% of the cases while and other variables have missing values but not to such a high level?</p> | 30,886 |
<p>I have an array of 12 subjects each of whom have 2 variables (i.e.right now I have 24 x 1 array..each subject repeated twice..). When I correlate this, I get a significant correlation. But because each subject is counted twice, I was told to jackknife on the subjects. While I understand the theory, I'm not sure how ... | 70,129 |
<p>Differential entropy of Gaussian R.V. is $\log_2(\sigma \sqrt{2\pi e})$. This is dependent on $\sigma$, which is the standard deviation.</p>
<p>If we normalize the random variable so that it has unit variance its differential entropy drops. To me this is counter-intuitive because Kolmogorov complexity of normalizin... | 70,130 |
<p>Please is anybody can explain me the principle of factor analysis (exploratory and confirmatory) that I will use in the validation of a questionnaire translated. Do I have to make a survey using the original and experimental Version or only the experimental version? And what is the sample size for this survey?</p> | 70,131 |
<p>I would like to somehow use the standard deviation of the following set of numbers to categorize values into five different groups. How would I do this? Do I take the max value of the set and divide by four, to get five equal parts?</p>
<p><strong>Set of numbers</strong>
1<br>
1<br>
1<br>
15<br>
22<br>
9<br>
99<br>... | 30,889 |
<p>I'm working on a Bayesian inference package and I have a function that finds the maximum a posteriori point. Right now I'm using scipy's <a href="http://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.fmin_bfgs.html" rel="nofollow">implementation</a> of BFGS to find that minimum of the log posterior, but... | 70,132 |
<p>I am trying to test if one algorithm is statistically significantly faster than another using the <a href="http://en.wikipedia.org/wiki/Student_t_test#One-sample_t-test" rel="nofollow">One-sample t-test</a></p>
<p>These are the results I have and I am trying to prove Algo2 is significantly faster than Algo1</p>
<p... | 70,133 |
<p>I'm trying to test the fit of two logistic regression models. I understand that deviance and AIC are good methods for this, but what if one model has better AIC but worse deviance? This is what I think has happened in my case. </p>
<p>Here's the summary/anova table from the first logistic regression: </p>
<pre><co... | 41,348 |
<p>My question is if there are any good online materials for learning this. Something that introduces things well, especially ARMA models and the related math. </p>
<p><strong>Edit:</strong> I'm looking for something of the high-end undergraduate level. Something like in Brockwell and Davis' <em>Introduction to Time S... | 30,890 |
<p>One often hears to say <em>"more than 70% variability is explained by ..."</em> What exactly is meant by this? Th proportion of the sum of squares (SSE), or mean sum of squares (MSE)? For example in the following anova table:</p>
<pre><code> Df Sum Sq Mean Sq F value Pr(>F) ... | 70,134 |
<p>I am trying to interpret data from previous research and I don't understand what the individual statistics (F, p, and np2--partial eta squared) are telling me about the data, or how they relate to each other to convey information about the data. For example, here are some of the information from Spruyt et al., 2009:... | 70,135 |
<p>I'm interested in <strong>identifying events</strong> (patterns) that <strong>occur before an event of interest</strong>.</p>
<p>For example, a customer calls in to complain or a customer checks their balance online then the customer closes the account (event of interest). Data is in a form of a sequence of events... | 30,891 |
<p>I have 10 different species with presence/absences data, as well as 6 different covariates relating to the design of marinas, including 3 continuous (lengths of walls, pontoons and groynes) and 3 factor variables (distance from freshwater, type of entrance and marina location). I have made binomial GLMs to assess wh... | 70,136 |
<p>I just thought I'd ask this question to see if there is a method or reasoning of proving a hypothesis test inversely, whilst logic remains the same.</p>
<p>I will use the following example, which I recently got confused over:</p>
<blockquote>
<p>Question: Test on a 5% level of significance if the model is
sign... | 70,137 |
<p>I'm pretty new to statistics and I need your help. I just installed the R software and I have no idea how to work with it. I have a small sample looking as follows:</p>
<pre><code>Group A : 10, 12, 14, 19, 20, 23, 34, 41, 12, 13
Group B : 8, 12, 14, 15, 15, 16, 21, 36, 14, 19
</code></pre>
<p>I want to apply t-te... | 49,842 |
<p>The time series is governed by the equation $S(T)=S(0)e^{(\mu-\frac{\delta^2}{2})T+\delta(w(T)-w(0))}$, in which $w(t)$ is a standard Brownian motion. Now given the data $\{S(t)\}_{t=0}^{t=T}$οΌ how to estimate $\delta$ and $\mu$?</p> | 70,138 |
<p>I do not understand how to arrange my data in SPSS for running MANOVA.<br>
I have 6 groups of participants that have rated 100 pictures on 3 different dimensions (dim1, dim2, dim3). </p>
<p>What I don't understand is this: </p>
<p>Do I have to use the mean value for the 3 dimensions (dim1, dim2, dim3) (say, mean ... | 70,139 |
<p>I am working with experimental data -correspondence test in the rental housing market-.
On which ground can I choose between: </p>
<ol>
<li>F.E. for the region where the apt is and cluster s.e. on the day the application to the apt was sent </li>
<li>cluster s.e. on region where the apt is and F.E. for the day t... | 70,140 |
<p>I have asked <a href="http://stats.stackexchange.com/q/61183/26179">question</a> concerning comparison between two groups. Got really nice answers and I want to perform downstream analysis using really good <a href="http://stats.stackexchange.com/a/61306/26179">gui11aume's suggestion</a>.<br>
But not everything is c... | 30,898 |
<p>I am trying to compute a regression.</p>
<p>I have a continuous dependent variable (investment in millions of dollars)<br>
One continuous independent variables<br>
Five dichotomous indicators (1 / 0)<br>
Four interactions.<br>
Robust standard errors are being used.</p>
<p>N=569.</p>
<p>Is there any particular rea... | 49,291 |
<p>I did a survey based on the <a href="http://en.wikipedia.org/wiki/Unified_theory_of_acceptance_and_use_of_technology" rel="nofollow">UTAUT</a> model / theory with standard questions used. The N was 150. I am trying to validate the model for my survey with structural equation modeling (via the AMOS software). But I h... | 70,141 |
<p>I have to make sure that a dependent variable I explain using linear regression ranges between a minimum of 0% and a maximum of 30% (it is an investment weight in a portfolio). How should I proceed ?</p> | 30,900 |
<p>Suppose I have a model that boasts given 1 year's daily data to calibrate the parameters, it could predict the behavior of future 1 month.</p>
<p>What should be the criterion for back-testing or, model validation?</p>
<p>Currently I calculate the error residuals and do Hypothesis testing:</p>
<ol>
<li><p>Calculat... | 70,142 |
<p>I have a set of 20 predictor variables, and I want to formulate a regression model by applying my own variable selection technique basically with backward approach (just for an experiment purpose.)</p>
<p>I'm rather new to <code>R</code>, and as far as I have studied so far, if I were to do it automatically I would... | 70,143 |
<p>I am estimating a model which gives me significant parameter estimates for my variables of interest. However, when I use the log version of the model log(dependent)=log(independent), I don't get significant estimates at the 95% confidence level.</p>
<p>I am replicating two other studies, and the authors do get sig... | 30,905 |
<p>If I have some share of a product in some sector as:</p>
<pre><code>2012 2013
50% 60%
</code></pre>
<p>and I find share change for 2012-13 then should it be 10% or 0.1?</p> | 70,144 |
<p><a href="http://www.ks.uiuc.edu/Publications/Papers/PDF/MART93B/MART93B.pdf" rel="nofollow">Neural gas for vector quantization</a>paper explains a technique for symbolizing or quantizing data. <a href="http://www.idiap.ch/~vincia/papers/neurocomputing.pdf" rel="nofollow">Algorithm</a> presents the algorithm in Secti... | 30,909 |
<p>I am analyzing rainfall water quality with cluster analysis first and then principal component analysis (PCA). There are 7 variables. Results from cluster analysis that extracting with PCA, almost of them show negative determinant, KMO very low (less than 0.3) and according to Barnett's test on sphericity, those dat... | 70,145 |
<p>So this question is about the BUGS modeling language. So you either know it or have no clue. I'm a newbie to this so it's been driving me mad. I want to define a simple two-state hidden Markov model (HMM) where the emission of each state follows a Normal distribution. I have an array data of Nxl dimension where each... | 70,146 |
<p>I am a muslim and there is ramadan going on. The last 10 days of ramadan are really special, and in one of these 10 days there is one special night that no one knows about.<br>
The special day is more likely to happen on the odd nights, but it can be on any day. </p>
<p><strong>How can the probability of a given da... | 70,147 |
<p>I'm doing a study on the determinants of FDI (Foreign Direct Investment) in the ASEAN countries. Before doing a panel data analysis, I'd like to run a Granger Causality Test between the potential FDI determinants time series (GDP, exchange rate, ecc.) and the FDI's one to support the choice of these variables for th... | 70,148 |
<p>Say for example you are doing a linear model, but the data $y$ is complex.</p>
<p>$ y = x \beta + \epsilon $</p>
<p>My data set is complex, as in all the numbers in $y$ are of the form $(a + bi)$. Is there anything procedurally different when working with such data?</p>
<p>I ask because, you will end up getting ... | 70,149 |
<p>In a conversation about Marsaglia's Multiply-With-Carry pseudo-random number generator and its potential use in generating random data for statistical purposes, someone said:</p>
<blockquote>
<p>There is no statistical simulation ever done that will use $2^{256}$ outputs from such a generator.</p>
</blockquote>
... | 22,199 |
<p>The problem which I have at hand consists of a logistic regression model for risk evaluation that has been made on some credit card data of Quarter-1'12 (Jan'12 - Mar'12). Now I use the same model to evaluate risk for the data of Quarter-2'12(Apr'12-Jun'12). I want to devise an accuracy score that gives an insight i... | 70,150 |
<p>What is a good introduction to statistics for a mathematician who is already well-versed in probability? I have two distinct motivations for asking, which may well lead to different suggestions:</p>
<ol>
<li><p>I'd like to better understand the statistics motivation behind many problems considered by probabilists.... | 111 |
<p>I have a data set which is highly imbalanced and I have used the SMOTE algorithm (using the R package DMwR) to balance the binary class in the data set. I have been using the R Ada package to then train an Ada Boost model on this data set to predict the binary class, with very good results.</p>
<p>In the same data ... | 70,151 |
<p>When adding a numeric predictor with categorical predictors and their interactions, it is usually considered necessary to center the variables at 0 beforehand. The reasoning is that the main effects are otherwise hard to interpret as they are evaluated with the numeric predictor at 0.</p>
<p>My question now is how ... | 70,152 |
<p>I am going to use the ARMA-GARCH model for financial time series and was wondering whether the series should be stationary before applying the said model.
I know to apply ARMA model the series should be stationary, however I'm not sure for ARMA-GARCH since I'm including GARCH errors which imply volatility clusterin... | 70,153 |
<p>There are many ways to measure how similar two probability distributions are. Among methods which are popular (in different circles) are:</p>
<ol>
<li><p>the Kolmogorov distance: the sup-distance between the distribution functions;</p></li>
<li><p>the Kantorovich-Rubinstein distance: the maximum difference between... | 70,154 |
<p>I have three clusters which is obtained by clustering features from images.
Lets assume I have two classes.
Consider the following table, where c denotes the class number and k denotes the cluster number and each entry denotes how many features from a particular class c falling into a cluster k.
.................k=1... | 49,843 |
<p>I have a (mixed) model in which one of my predictors should a priori only be quadratically related to the predictor (due to the experimental manipulation). Hence, I would like to add only the quadratic term to the model. Two things keep me from doing so:</p>
<ol>
<li>I think I read somehwere that you should always ... | 49,477 |
<p>I have some problems in understanding the results of two linear regressions on the same data.</p>
<p>I have 2 variables and I want to know if there is a linear correlation between the two. Let's say velocity of a car and perceived velocity of the conductor.
Let's say I have 4 velocities and 2 evaluations of the per... | 46,045 |
<p>I am using the randomForest package in R (R version 2.13.1, randomForest version 4.6-2) for regression and noticed a significant bias in my results: the prediction error is dependent on the value of the response variable. High values are under predicted and low values are over predicted. At first I suspected this wa... | 30,917 |
<p>Coming from the field of computer vision, I've often used the <a href="http://en.wikipedia.org/wiki/RANSAC">RANSAC</a> (Random Sample Consensus) method for fitting models to data with lots of outliers. </p>
<p>However, I've never seen it used by statisticians, and I've always been under the impression that it wasn'... | 70,155 |
<p>I once read (unfortunately I cannot find the source anymore) that oversampling is only "allowed" when the class distribution is very, very skewed, i.e. 1:99 or worse. </p>
<p>So in my case I have a class distribution of 30:70. When don't apply oversampling in my neural network (10-20-1, sigmoid (hidden layer), sof... | 15,997 |
<p>I have time series as </p>
<pre><code>0.4385487 0.7024281 0.9381081 0.8235792 0.7779642 1.1670665 1.1958634 1.1958634 0.8235792 0.8530141 0.8802216 1.1958634 1.1235897 1.3542734 1.3245534 0.9381081 1.1670665 1.1958634 0.8802216 1.3542734 1.1670665 4.9167998 0.9651803 0.8221709 1.1070461 1.2006974 1.3542734 0.965180... | 34,759 |
<p>I'm looking for a learning algorithm to analyze data, then group it and define how many classes are fit to distinguish the data set. Type of experiment is in the context of evolutionary biology, how a set of bacteria evolve over the course of time.</p>
<ol>
<li><p>The data is initially unlabeled so I'm assuming I s... | 70,156 |
<p>I am running an analysis where I have 2500 cases and 2500 controls. The cases have disease A, and the controls do not. I am trying to see if having disease A increases the odds of various diseases. For the sake of simplicity, we can focus on one disease, call it disease B.</p>
<p>D = 1 if disease B present, 0 other... | 33,736 |
<p>There are lots of machine learning toolkits nowadays, such as <em>weka</em>, <em>sklearn</em>, <code>R</code> libs. If we choose to use these toolkits, besides that it is convenient, sometimes we might lose control of what is really happening.
For example, in some learning methods the value of features should be sc... | 30,921 |
<p>This is a follow-up of a question that I posted previously. I'm trying to get parameter estimates from two different SAS functions (<code>Proc REG</code> and <code>Proc GENMOD</code>) to equal each other when run on the same data set. <code>Proc REG</code> uses OLS/WLS to estimate parameters; <code>Proc GENMOD</co... | 34,841 |
<p>Does anyone know how to graph changes in a dependent variable <em>over time</em>, based on changes in <em>several</em> independent variables (i.e., graphs for panel data regressions)?</p> | 30,923 |
<p>I am looking for a good reference book for applying statistics to medical problems. I am interested in a practical book that describes concepts including statistical power, tests for comparing groups, and regression analysis in the context of medical problems.</p> | 30,924 |
<p>I have read a number of times about computing p-values in bootstrapping.</p>
<p>Unfortunately, I could not use none of them.</p>
<p>Maybe you can help me, please?</p>
<p>I obtained 10000 bootstrap resamples of the difference between the means of two groups of data.</p>
<p>I also got the confidence interval for t... | 49,844 |
<p>All my predictors are binary in nature. So far I have been building the model with the logistic fuction. Could anyone suggest any appropriate statistical technique keeping the following points in mind:</p>
<ol>
<li>Dependent variable - binary</li>
<li>All Independent variables - binary </li>
<li>Re... | 70,157 |
<p>I've seen in a <a href="http://www.kaggle.com/c/digit-recognizer" rel="nofollow">kaggle challenge about digit recognition</a> someone who used <a href="https://en.wikipedia.org/wiki/Principal_component_analysis" rel="nofollow">PCA</a> before decision tree or other techniques.</p>
<p>I thought it was just for compre... | 41,390 |
<p>I have collected data from two groups (age 25-30, age 30+). In each group I have 10 patients. I performed several medical tests (i.e., R.B.C, Liver test, etc.) on the patients, before and after treatment.</p>
<p>The data look like this:</p>
<pre><code>Group 1
Test1 ... Test ... | 70,158 |
<p>I'm sure there's a more technical term for what I'm looking for, but I don't know what it is (it's not confidence intervals, I think)</p>
<p>I'm trying to make a system where people get ratings (from 1 to 5 stars) over time, and I want to combine all those ratings into one individual score for each person. Now, thi... | 70,159 |
<p>I am using generalized linear models with one response variable and 6 predictors (1 covariate and 5 factors). I want to assess the effect of smoking on my response variable. When I split my participants in sex groups and then in three smoking groups (smokers, ex-smokers, non-smokers) I find weaker associations than ... | 30,929 |
<p>I have six questions that each have a five-point Likert scale. We are interested in whether participants, overall, "agree" or "disagree" (or are neutral) toward the questions.</p>
<p>To do this, we currently calculate the average of the items, which results in an average from 1 to 5, then we collapse it into 3 bins... | 37,913 |
<p>Is there <a href="http://projecttemplate.net" rel="nofollow">ProjectTemplate</a> equivalent in python? I.e. a template that defines and helps carry out an efficient workflow for a statistical project?</p>
<p>If there is nothing specifically designed for statistics, has anyone successfully used a more generic python... | 30,931 |
<p>I am trying to calculate the power that I will have to detect an interaction between 2 different interventions in a 2X2 factorial design. We aim to have about 850 participants in each of the four boxes, or roughly 1700 per arm for a total of 3400. The study outcome is prevalence at 2 years, with expected prevalence ... | 30,932 |
<p>I have a problem where I want to use a classifier for it. So I defined a set of features and created a dataset. Now I want to generate some plots to understand the features. I came across the Scatterplot Matrix or the Correlation Matrix, but I'm so confused about if they are the same thing or not.</p>
<p>1 - <a hre... | 70,160 |
<p>Hi guys I am trying to writ e a code on python to correct forecast data using Kalman Filter.
I am following the equations and recommendations in this link : <a href="http://www.swarthmore.edu/NatSci/echeeve1/Ref/Kalman/ScalarKalman.html" rel="nofollow">http://www.swarthmore.edu/NatSci/echeeve1/Ref/Kalman/ScalarKalma... | 34,890 |
<p>I understand that PCA is used for dimensionality reduction to be able to plot datasets in 2D or 3D. But I have also seen people applying PCA as a preprocessing step in classification scenarios where they apply PCA to reduce the number of features, then they use some Principal Components (the eigenvectors of the cova... | 30,934 |
<p>Could you help me prove that the following sequence of independent random variables satisfy Weak Law of Large Numbers?</p>
<p>$$P(X_n = n - \sqrt{3}) = P(X_n=-n- \sqrt{3}) = \frac{1}{2} $$</p> | 70,161 |
<p>I have a data set with 1500 individuals who were surveyed about many things including demographics, attitudes and opinions about politics and economic status. The most important question in the survey was about vote intention on the next election for president. The question had the four candidate options, plus optio... | 30,937 |
<p>I just ran my first ever PCA, so please excuse any naivety on my part.</p>
<p>As input, I used five years worth of the following:</p>
<ul>
<li><a href="http://au.spindices.com/indices/equity/sp-asx-200-a-reit-sector" rel="nofollow">S&P/ASX 200 A-REIT</a></li>
<li><a href="http://au.spindices.com/indices/eq... | 70,162 |
<p>What can I read that will give me a meta-view of the diverse field of statistics and data science? With few exceptions much of what I get my hands of goes straight into formulae and methodologies. Preferably something sufficiently high level as to bring in diverse areas such as econometrics, psychometrics, machine l... | 70,163 |
<p>The expectation of a function $f(x)$ over a probability distribution $p(x)$ where $x=(x_1,\dots,x_n)$ and $x_i \in \left\{1,\dots,K\right\}$ requires a summation over all possible $K^n$ combinations. </p>
<p>$ E[f(x)] = \sum_x f(x)p(x)$</p>
<p>For large scale systems this exponential grow up is formidable. I am wo... | 70,164 |
<p>This is a simple question about notation.</p>
<p>Let $\mathbf{p}$ be a Bayesian prior.
Let $\mathbf{x}$ be the data, which is a random vector.
Let $\mathbf{S}$ be some indexing set for $\mathbf{x}$.
Then I've used the notation $\mathbf{x}_{\mathbf{S}}$ for the restriction of $\mathbf{x}$ to $\mathbf{S}$, and $\mat... | 30,940 |
<p>Is there any way to run an OLS difference in differences model when the dependent variable (investment) has lots of observations which are truly zero?</p>
<p>I donΒ΄t know how to add clarifications. My problem is indeed the normality assumption. I am using firm level panel data. Many firms (around 60%) do not invest... | 70,165 |
<p>I have the following data in R</p>
<pre><code>x <- c(0.1,0.2,0.3,0.6,0.8,0.9,1)
y <- c(90,96,97.7,99.3,99.65,99.95,100)
</code></pre>
<p>I'm trying to find a logarithmic equation that best fits these points. I'm not sure what the equation would look like, but probably something like one of these</p>
<ul>
<l... | 41,402 |
<p>A parameter of an object is normally distributed with a mean <code>m</code> and a std. dev. <code>s</code>. If <code>r</code> such objects are randomly selected, what is the maximum <strong>expected</strong> value <code>M</code> of the parameter in the selection?</p>
<p><sub>Cross-posted from: <a href="http://matho... | 70,166 |
<p>If I have a population of vectors in R$^n$ and some special subset has a different distribution, I could try and use PCA to describe the main axes of these distributions and, if they are aligned differently, that would give me a quick way to describe the difference in orientation between the two. However PCA is depe... | 70,167 |
<p>I conducted a experiment where I measured bacteria on a 1000 peoples' hands after performing a repeatable task. </p>
<p><img src="http://i.stack.imgur.com/8wbDy.png" alt="enter image description here"></p>
<p>This scatter graph shows 2 experiments where the humidity of the hands is changed.
I then repeated the ex... | 70,168 |
<p>If I have a fixed effects model where data is separated by states over time, how would the coefficient interpretation on variables differ from an OLS interpretation? And how would I interpret the intercept?Thank you.</p> | 70,169 |
<p>I'm calculating the covariance of a distribution in parallel and I need to combine the distributed results into on singular Gaussian. How do I combine the two?</p>
<p>Linearly interpolating between the two almost works, if they are similarly distributed and sized.</p>
<p><a href="http://en.wikipedia.org/wiki/Algor... | 49,287 |
<p><br>
I have a binary DV and my panel data set contains more than one observation
for only 20% of the subjects which makes it very unbalanced.
Is there anything methodologically wrong with doing a mixed model with data that looks like this,i.e. with many subjects having only one observation?
I'd appreciate any hints... | 30,948 |
<p>This morning I woke up wondering (this could be due to the fact that last night I didn't get much sleep): since cross-validation seems to be the cornerstone of proper time-series forecasting, what are the models I should "normally" cross-validate against?</p>
<p>I came up with a few (easy) ones, but I soon realized... | 41,406 |
<p>I am trying to forecast the sales of products in vending machine. The problem is that the machine is filled at irregular intervals and at every fill we only can record the aggregated sales since the last fill of the machine (i.e. we don't have daily sales data). So basically we have data for aggregated sales at irre... | 30,951 |
<p>I performed a random forest using the <code>randomForest</code> package. I know that if I plot the random forest using the <code>plot()</code> command, I should get back a graph with number of trees on the x-axis, and estimated error rate on the y-axis, but when I actually plot it, I get multiple curves, all of them... | 41,410 |
<p>I have too many environmental variables to use in a multiple regression analysis. If I use all the variables the models are just too complex. The use of the PCA axes in the regression analysis was impossible to interpret (since there wasn't a clear correlation with environmental variables), so we chose to select a l... | 41,411 |
<p>I understand the effect of a categorical random effect on a mixed effects model in that it performs a partial pooling of the observations by level in the random effect, effectively assuming that the observations aren't independent themselves but only their partial pools are.
Also to my understanding, in such a model... | 30,953 |
<p>I am trying to find the best fit between an species dataset and prevailing climatic conditions, in order to be able to predict the environmental conditions from the species dataset (paleoclimate research). </p>
<p>I have 15 species(sp1-sp15), expressed as relative amounts (some are 0).
I have done some data explora... | 70,170 |
<p>I'm planning on starting a ANN classification project pretty soon. It will use 15 input variables (medical data with 25k records) to predict an outcome. I have been following the ML course on Coursera, where Octave is used, but I'm used to <code>R</code>. I've been reading about ANN in <code>R</code> and I got the f... | 30,955 |
<p>I am just a beginner in machine learning and finding tough time to understand few concepts. I have 10 strings of characters of length 50 each. These are the training data $T(i)$ for $i=1:10$. The first 5 come from class $A$ and next 5 from class $B$. Then there is an incoming string\test Test of same length. I calcu... | 35,005 |
<p>I've always thought the emergence of the normal distribution was kind of magic, specifically that $\pi$ and $e$ both emerge in the distribution, even though they don't exist in the binomial.</p>
<p>I've googled heavily, but haven't found a very good guide showing how these constants arise, but would like to see it.... | 30,958 |
<p>Recently, I have read an article which name is β<a href="http://www.ncbi.nlm.nih.gov/pubmed/9618776" rel="nofollow"><em>Feed forward neural networks for the analysis of censored survival data: A partial logistic regression approach</em></a>β.</p>
<p>Without a math background, I catch only a little about the ANN app... | 70,171 |
<p>I'm performing Classical MDS on the distance over columns of binary matrix. The result is like this:</p>
<p><img src="http://i.stack.imgur.com/XkB9J.png" alt="enter image description here"></p>
<p>The points lies on two lines vertical to each other. I don't think useful information is shown in this MDS chart. So I... | 30,960 |
<p>I have a prediction outcome that is dichotomous while all other predictor variables are binary and categorical. </p>
<p>How can I perform cross validation in SAS and see the ROC curve?</p>
<p>I need to create bayesian network. </p> | 41,414 |
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