question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>I am interested in generating correlated, skewed data in order to evaluate the application of a statistical approach to a data set I am analyzing. Specifically, I have two correlated variables, and I can determine the correlation coefficient ($R^2$) between the two, as well as the shape, scale and location of each s... | 30,562 |
<p>I'm working on merging records from several databases that cover the same entities, but share no reliably deterministic fields, leaving us with fields such as name and address to resolve identity. In reading about this problem I came across the Fellegi-Sunter statistical method for resolving record linkage.</p>
<p... | 69,896 |
<p>I've read that if two time series, $Y_t$ and $X_t$, are trend stationary, then regressing $Y_t$ on $X_t$ results in a spurious regression <em>because of an omitted time trend variable</em>. Let $Y_t = \delta_0 + \delta_1t + u_t$ and $X_t = \gamma_0 + \gamma_1t + v_t$. I want to show that $Y_t$ is a linear function o... | 69,897 |
<p>So there's a textbook question I stumbled upon:</p>
<p>A marketing research firm estimates the proportion of potential customers preferring a certain brand of lipstick by "randomly" selecting 100 women who come by their booth in a shopping mall. Of the 100 sampled, 54 stated a preference for Brand A.</p>
<p>How wo... | 69,898 |
<p>I have the following exercise question that I would like insight on:</p>
<p>A legal case is being formulated by a union of secretaries who claim that they are being paid unfairly low wages by their employer.</p>
<p>The 64 secretaries in the firm have an average annual salary of \$38300 with a SD of \$840.
The aver... | 30,565 |
<p><em>NOTE: my limited experience is with Random Forest using R.</em></p>
<p>Are there any special considerations when using Random Forest (in R) that I should be aware of with respect to the impact of correlated variables or variables derived from other variables in the dataset?</p>
<p>For example if I am trying to... | 11,946 |
<p>If one variable is normal distributed and the other is non normal distributed, which kind of correlation do we use?</p>
<p>I am not sure which correlation is right to use.</p> | 69,899 |
<p>I would like to estimate Poisson means from data sets where means are usually in the range 0.5 to 10. 0 (zeros) in the data are unambiguous; estimates of higher-event numbers degrade in rough proportion to the number of events.</p>
<p>This R code is a reasonable data simulator:</p>
<pre><code>data<-rpois(100, ... | 30,570 |
<p>I have 6 months of observation during which "clinical events" can happen. The endpoint during this period is a hospitalization (or censoring). I want to develop estimates of the the likelihood of a hospitalization happening within 10, 7, and 3 days of the "clinical event" using survival analysis. Is this possible... | 69,900 |
<p>Two of my independent variables are correlated with the dependent variable but in multiple regression they turned out to be insignificant predictors of the same. </p>
<p>Is it possible? and how to report this difference in data interpretation? </p> | 49,368 |
<p>I am testing the reproducibility of two drug concentrations between two sites of the same individual. I am assuming response between sites should be similar. To test the significance I created a scatter plot and did a paired t test in R.</p>
<p>The results were: </p>
<pre><code>t = 1.1419, df = 44, p-value = 0.259... | 69,901 |
<p>I have explanatory variable age in the model (along with others) and there are several theoretical justification for using square of age variable (along with age) in the model,e,g,<a href="http://stats.stackexchange.com/questions/19823/why-would-one-use-age-squared-as-a-covariate-in-a-genetic-association-study">here... | 69,902 |
<p>While attempting to analyze error incurred in certain optics experiments, I am only able to make statements about the standard deviation of a suitable distance measure between the actual and expected outcomes. </p>
<p>I understand that the standard deviation is not <em>always</em> a good measure of error, for examp... | 69,903 |
<p>I will approximate a given probability distribution $P$ over $\mathbb{R}^n$ with a distribution $\tilde{P}$ which is simpler to represent. I would like to keep track of the error that I'm making through this approximation. </p>
<p>Q1: What are some good notions of error in this context?</p>
<p>I will then sample f... | 30,574 |
<p>I am used to make my data plots with R and to save the results to static files but now I have a data set with far too many data points and I need to explore it. Due to this I need a recommendation for an interactive tool for plotting (2D) data. It should be able to interactively filter and search points by additiona... | 38,151 |
<p>I used a least squares method on my data set, using the <code>lsqr</code> Matlab function. I know that the norm of residuals is a measure of the goodness of fit, but how can I assess whether the value of the norm of residuals is "good"? Which is the range of this measure?</p> | 69,904 |
<p>Is it possible to apply the law of the iterated logarithm (e.g. <a href="http://en.m.wikipedia.org/wiki/Law_of_the_iterated_logarithm" rel="nofollow">http://en.m.wikipedia.org/wiki/Law_of_the_iterated_logarithm</a>) to derive non-trivial (i.e. bounded) 100% confidence intervals for population averages?</p>
<p>An ab... | 69,905 |
<p>I am empirically checking Fama & French three factors (market, SMB, HML - independent variables) model on a Viet Nam stock exchange. The dataset is daily stocks' return during almost 4 years. The stocks are grouped in six portfolios - each is dependent variable in each regression. I would like to test the validi... | 69,906 |
<p>I have a random variable $X$, which can take $n$ values and is distributed according to multinomial $\Theta=(\theta_1, \theta_2, \cdots, \theta_n)$. I observe a random variable $Y$, where I have that $P(Y=j|X=i)=c_{j,i}$. </p>
<p>Let $C$ be the matrix $[C_{j,i}]_{1\leq j,i \leq n}$. I have that $C$ is a full rank m... | 69,907 |
<p>I ran a survey on a population of advisors in all the different recruitment centers of in a country. I had 1410 text written entries (not multiple choice)
I took a sample of 284 to see what are the top 10 mistakes done by job seekers during interview.</p>
<p>My goal is to infer my result to the population of all ad... | 69,908 |
<p>For $n$ distinct observations, there are ${2n - 1 \choose n-1}$ distinct bootstrap (re)samples.</p>
<p>Could someone please provide a simple explanation? </p>
<p>I found <a href="http://statweb.stanford.edu/~susan/courses/s208/node11.html" rel="nofollow">http://statweb.stanford.edu/~susan/courses/s208/node11.html<... | 69,909 |
<p>I have both continuous and categorical data and my data are not normal. which test should I use instead of one-way ANOVA? A Kruskal-Wallis test?</p> | 69,910 |
<p>I am trying to understand a neuroscience article by Karl Friston. In it he gives three equations that are, as I understand him, equivalent or inter-convertertable and refer to both physical and Shannon entropy. They appear as equation (5) in the article at <a href="http://www.fil.ion.ucl.ac.uk/spm/doc/papers/Action_... | 69,911 |
<p>Say I have multivariate normal $N(\mu, \Sigma)$ density. I want to get the second (partial) derivative w.r.t. $\mu$. Not sure how to take derivative of a matrix.</p>
<p>Wiki says take the derivative element by element inside the matrix. </p>
<p>I am working with Laplace approximation
$$\log{P}_{N}(\theta)=\log... | 69,912 |
<p>I have both time series data and moving average data for the same data-set and the same time interval. I would like to extract the overlapping points. I would like extract those points where the extremum between the current and the last crossing point (intersected point between Moving average and time series) is tak... | 69,913 |
<p>I'm looking to run rolling one-step ahead forecasts on the Mcomp holdout data (future data), with re-estimation at each point, i.e. re-estimation over the entire historical and already forecast holdout data. As Mcomp is partitioned into historical (x) data and future (xx) data, I am unsure of how to step through to ... | 69,914 |
<p>I am seeking to characterize time-series data (specifically parameters derived from sensor data) for 18 patients collected over 20 days using autocorrelation (see plot below of autocorrelation functions for 18 patients for a given sensor parameter). </p>
<p>I want to see if I can use the autocorrelation function va... | 30,587 |
<p>I am analyzing a case-control study on patient given dose effect to outcome (recovery or not). The control patients were matched according to age (5-year per category) and performance status (PS). As a result, I ended up with 30 pairs (variable PairID) of patients and I would like to apply a logistic regression to e... | 69,915 |
<p>Techniques like Adaboost use a ensemble of weak classifiers to obtain a "better" classifier.</p>
<p>Does(Can) the final classifier have a greater VC-dimension than the weak classifier? </p>
<p>An intuitive explanation would suffice.</p> | 30,588 |
<p>This data is for a company who wants to minimize their expenses. The expenses is described out of the production costs . (Production, salary, capital and material prices). I need to create a regression model, which explains the expenses as good as possible by using R.</p>
<pre><code> Expenses Production Sal... | 69,916 |
<p>What is the least painful way to do the following in R? We want to run a model with a formula like this:</p>
<pre><code>Model #1: Speed ~ male + female
</code></pre>
<p>Unfortunately, our data frame has just a single column, <code>Gender</code>, which has levels <code>'female'</code>, <code>'male'</code>, and <co... | 69,917 |
<p>this is a repost from math.stackexchange (I didn't know how to migrate the post, apologies). I was informed that this would be a better place to ask.</p>
<hr>
<p>TLDR: I am trying to do maximum likelihood fitting of a dataset having two mixed populations, observed over a subset of their parameter space, within it ... | 15,877 |
<p>I have taken a sample of $n$ data points from a population. Each of these points has a true value (known from ground truth) and an estimated value. I then calculate the error for each sampled point and then calculate the RMSE of the sample.</p>
<p>How can I then infer some sort of confidence interval around this RM... | 69,918 |
<p>Say that I get an attendance list of people in a party. From another source I know the minimum and maximum age of each person with a name e.g. "John" must be between 19 and 55 or "Mary" must be at least 32. <br>
I want to evaluate the distribution of people ages in the party from this data i.e. categorical distribut... | 69,919 |
<p>Now, $X$ is my IV and $Z$ is the DV. In my analysis, I also have a mediating Variable $Y$. The significant $\beta$ while doing MRA between $X$ and $Z$ is <code>-.85</code>. Other conditions being satisfied, when I had MRA between $X$ and $Z$ with mediating variable $Y$, the sig. $\beta$ is <code>-.32</code>. Here i... | 40,931 |
<p>Suppose we have a dataset of people that can be described with a mix of some continuous variables (eg height, age) some ordinal (eg social status) and some categorical (eg city, car brand, favourite color, ethnic group etc). Now, the trick is that the cardinality of categorical data is big (eg there are 1000 cities,... | 32,668 |
<p>So I have this joint dist </p>
<p>$$f(x,y) = \frac{1}{2\pi}\exp(-\frac{x^2}{2} - \frac{y^2}{2} + x^2y - \frac{x^4}{2})$$</p>
<p>I'd like to find $f_x(x)$. So I know that means I need to integrate function wrt y. So my strategy is to pull out whatever terms I can so some of it will look like the normal dist then ... | 40,933 |
<p>I'd like to generate a new point which should be uniformly distributed on the interval [a, b) (i.e. including the left extreme value - a and exluding the right extreme value - b). The <code>runif</code> help says:</p>
<blockquote>
<p>runif will not generate either of the extreme values unless max = min
or max-m... | 11,955 |
<p>I have been using log normal distributions as prior distributions for scale parameters (for normal distributions, t distributions etc.) when I have a rough idea about what the scale should be, but want to err on the side of saying I don't know much about it. I use it because the that use makes intuitive sense to me,... | 43,503 |
<p>I want to use a t distribution to model short interval asset returns in a bayesian model. I'd like to estimate both the degrees of freedom (along with other parameters in my model) for the distribution. I know that asset returns are quite non-normal, but I don't know too much beyond that.</p>
<p>What is an appropr... | 69,920 |
<p>I would appreciate any help in trying to calculate the Cumulative Distribution Array of a Probability Mass Array when dimensions > 2, essentially a discrete joint cumulative distribution from a sample of data. MATLAB syntax would be most preferred. In a bivariate case (2 dimensions), the following works well:
<cod... | 30,598 |
<p>So, I'm working on this homework problem and am really unsure how to go about it. I'm working with an online software, which gives me the answers to the questions, but I have no idea how to get to those answers. I understand why the degrees of freedom is 2, but that's about all. If anyone could guide me in the right... | 69,921 |
<p>Assume I have a random vector $X = \{x_1, x_2, ..., x_N\}$, composed of i.i.d. binomially distributed values. If it would simplify the problem substantially, we can approximate them as normally distributed. Given that all other parameters are fixed, I want to know how $E[min(X)]$ (the expected value of the smalles... | 69,922 |
<p>This may be hard to find, but I'd like to read a <strong>well-explained ARIMA example</strong> that</p>
<ul>
<li><p>uses minimal math</p></li>
<li><p>extends the discussion beyond building a model into using that model to forecast specific cases</p></li>
<li><p>uses graphics as well as numerical results to characte... | 49,888 |
<p>I have time-series data for stock price. A sample of dataset is given below:</p>
<pre><code>DATE STOCK_PRICE
1/7/2012 26
1/8/2012 31
1/9/2012 28
1/10/2012 38
1/11/2012 36
1/12/2012 20
1/13/2012 23
1/14/2012 23
1/15/2012 1.1
1/16/2012 1.4
1/17/2012 1.9
1/18/2012 2.3
1/19/2012 5.8
1/20... | 69,923 |
<p>I need to explore the determinants of wheat yield using multiple regression. There are 120 observations. Do I need to use ANOVA? I am using R studio. My results need to include a consideration of more than one functional form, one or more interaction terms for a select set of variables, and the use of dummy variable... | 40,945 |
<p>I am investigating unconscious racial prejudice as a predictor for guilty or not guilty judgements (Using SPSS).</p>
<p>I have a continuous variable for unconscious racial prejudice (higher numbers equal higher levels of racial prejudice), which I want to see if it can predict future judgements of guilt. My depende... | 30,602 |
<p>I have run a repeated measures ANOVA using 3 groups and one factor with two levels. </p>
<p>I have discovered that the data are not normally distributed (but not badly), nor is the variance homogeneous in either of the factor's conditions across groups. </p>
<p>If the data are not normal, I would use a Kruskal-Wal... | 69,924 |
<p>I am working with the survivorship bias free database of hedge funds and trying to estimate the persistence of performance in the future performance of such funds based on the past performance. In this research I follow the approach of Horst and Verbeek, see for example: </p>
<p>ter Horst, J.R. & Verbeek, M.J.C... | 69,925 |
<p>I am using R and I have been analysing my data with GLM with Binomial link. </p>
<p>I want to know what is the meaning of the intercept in the output table. The intercept for one of my models is significantly different, however the variable is not. What does this mean?</p>
<p>What is the intercept. I don't know if... | 69,926 |
<p>I'm writing a computer program to automatically detect black noisy borders on scanned images and crop them off.
My algorithm is based on 2 variables: gray mean value (of the pixels in a rows/columns) and position (of a row/column in the image).</p>
<h3>Gray Mean Value</h3>
<p>Images are in gray scale: this means t... | 30,605 |
<p>I have never taken part in an official or structured data analysis or machine learning course (other than recent online offerings) and have learned most of what I know from reading and trying things out. I know I am far away from being able to get a job.</p>
<p>My question isn't what is better (<a href="http://stat... | 69,927 |
<p>Suppose we have a continuous-time stochastic process $X(t)$, which consists of a sequence of delta functions that, at each time $t$, have a probability $p(t)$ of taking a non-zero value. $p(t)$ lies in $[0,1]$ for all $t$ and just a scaled survival function of an exponential distribution, so $p(t)$ is decreasing in ... | 40,954 |
<p>My dataset consists of 4 variable: <code>values, dil, exp and sample</code>. There are 170 values obtained for variable values; there are 5 levels for the variable <code>dil</code>, 10 levels for the variable <code>exp</code> and 5 levels for the variable <code>sample</code>.</p>
<p>I fitted a mixed model in <code>... | 30,609 |
<p>I have a 24983 X 100 matrix. The cell (i, j) in the matrix, indicates the rating for joke number j by user number i. I need to recommend to user i the joke would make him laugh the most. </p>
<p>I need to use supervised learning, for example SVM, by dividing the matrix into two groups (train and test, using cross-v... | 69,928 |
<p>The following question is part (1/4) of a 2.30h written exam for the course "Probability and Statistics" in a school of engineering. So, although tricky and difficult (because the Professor is really demanding from his students), it should be solvable in a logical amount of time and with a logical amount of calculat... | 69,929 |
<p>Would I use the same type of multiple regression approach to build a forecast model for sales in one region as I would if I wanted to forecast sales in 5 regions. I was told that I should use an ARIMA with regressors to model one region. It appears in R this is autoarima if more than one region this is plm. Why? By ... | 69,930 |
<p>I am not familiar with degree of freedom. Here are some related questions:</p>
<ol>
<li>Assume $x$ follows $lognormal$ distribution: $x$~$lognormal(\mu,\theta)$. Fit a dataset {$x$} (with $N$ $x$'s). What is the degree of freedom? </li>
<li><p>$Fx=(Fx|A)^a*(Fx|B)^b$, $x|A$~$lognormal(\mu1,\theta1)$, $x|B$~$lognorma... | 69,931 |
<p>I am confused with using <code>mlogit</code> package to <strong>build a multinomial logit model</strong>. In my data the only variables I have are the <strong>individual specific variables</strong>, to be consistent with terms from the <code>mformula()</code> method description (from the <a href="http://cran.r-proje... | 69,932 |
<p>I am new to deep learning... please help me out..</p>
<p>When is cross entropy function better than squared error function in neural networks. Why is cross entropy function better in classification problems? </p>
<p>I am coding an auto encoder. Inputs range from o to 1. Which cost function would be better?</p>
<p... | 69,933 |
<p>I have feature set 1 and feature set 2. If a linear kernel SVM performs better ("better" meaning greater classification accuracy) when using feature set 1, does this guarantee that a properly tuned rbf kernel SVM will also perform better using feature set 1?</p>
<p>Thanks for the help.</p> | 69,934 |
<p>I'm a newcomer in Machine learning (also some statistics), been learning knowledge (supervised/unsupervised learning algorithms, relevant optimization methods, regularizations, some philosophies (such as bias-variance trade-off?)) for a while. I know that without any real practice, I would gain deep understanding of... | 69,935 |
<p>Unscented transform can approximate expectations well via deterministic sampling.
if $f(x) = N(\mu,\Sigma)$ and $x\in \mathbb{R}^d$ then
$\int f(x) h(x) \approx \frac{1}{2d}\sum_{i=1}^{2d} h(x_k)$ where $x_k$ are the so called sigma points that are chosen as
$ x_k = \mu \pm (\sqrt{d\Sigma})_k$ where $(\sqrt{\Sigma}... | 69,936 |
<p>I am trying to figure out the proper way to compare the quality of two estimators of a parameter based on data. The basic approach I've taken is to compute the MSE of the empirical bootstrap distribution of each estimator, but then <strong>the question is</strong>: how do I put "error bars" on these MSEs, to see if ... | 69,937 |
<p>I am coding an auto encoder with mnist data. It have 784 inputs, 50 hidden units, 784 outputs. Since outputs are huge in number, when error gets propagated during gradient descent, error of hidden units is quite huge. This resulted in large gradients. So, weights are getting updated heavily. This resulted in saturat... | 162 |
<p>Basically, I am playing around the <code>mixture.example</code> dataset from ESL. And the pdf below (page 7) gave the code to reproduce Figure 2.5 in ESL . </p>
<p><a href="http://cran.r-project.org/web/packages/ElemStatLearn/ElemStatLearn.pdf" rel="nofollow">http://cran.r-project.org/web/packages/ElemStatLearn/Ele... | 30,614 |
<p>I'm trying to fit a mixed model of my data, but I'm getting the estimated between-subject standard deviation equal to zero. I need to estimate the between-subject standard deviation and within-subject standard deviation in my fit model. This is my data and code:</p>
<pre><code>require(lme4)
data <- data.frame(C... | 11,963 |
<p>I have a VAR model in which I regress the monthly unemployment rate on itself lagged one month, the monthly GDP percent growth lagged by two months and two dummy variables. I am trying to test for the existence of autocorrelation in the residuals in my model. Using the autocorellation graphs for variables I conclude... | 30,615 |
<p>Hoping to get some advice from someone knowledgeable in Record Linkage. </p>
<p>Let's assume the following:</p>
<pre><code>m-probability: 0.95
u-probability: 0.10
</code></pre>
<p>The m-probability is the probability that two fields match given they represent the same entity. The u-probability is the probability ... | 69,938 |
<p>For a multi-class classification problem, we can use $K$ binary logistic classifiers, or one softmax regression classifier, so how to make the choice between the two?</p>
<p>IMHO, the $K$ binary logistic classifiers is just the <strong>1-vs-all</strong> scheme for multi-class, but softmax classifier inherently hand... | 69,939 |
<p>I'm looking at attempting to capture the regularity of a time series of events, one measurement per day, with a year's worth of data, and there can be at most one event a day. Say for example the day you do laundry. What I want to capture is a measurement of regularity. Capturing irregularity is straight forward: go... | 69,940 |
<p>I am trying to learn a L2 regularized Logistic regression model in liblinear. I need a way to specify the C parameter which I do by cross validation.</p>
<p>However, the loss/accuracy measure in cross validation is percentage. I want more of like logistic loss or AUC. How can I do it in liblinear or is there any wa... | 69,941 |
<p>I have this web application where I need to map consumer preferences based on some input information and individual choices. My goal is to create a list of product recommendations and evaluate the level of “importance” of these products with respect to the user. </p>
<p>From my research so far I realize that there... | 458 |
<p>Consider a Metropolis-Hastings walk over an exponentially large, known state space S. The proposal/transition matrix P is known, as is the target stationary distribution. In fact, assume there is an efficient algorithm Propose_P(s,c) that, if provided sufficiently long uniform sequence of "coins" c, will sample ac... | 30,616 |
<p>(i) Is it true to say that if the sample frame is not a random selection (such as a convenience sample), then the sample frame is not representative of the true population?</p>
<p>(ii) We can always do a G*Power analysis to determine the sample size. But how do we determine if the sample frame represents the true p... | 69,942 |
<p>Let $Z=(X+Y)/2$, where $X$ and $Y$ are independent normally-distributed random variables with known variances $\sigma^2_X$ and $\sigma^2_Y$ and unknown (and possibly different) means. Given a sample $x_1$ from $X$ and $y_1$ from $Y$, what is the maximum likelihood estimator of the mean of $Z$?</p> | 40,965 |
<p>It occurred to me that, while I've pieced together some ideas over the years about the differences between statistics and biostatistics, I've never heard a formal explanation. What is the distinction between these two disciplines (currently)? And why did this distinction begin in the first place?</p>
<p>EDIT: I'v... | 30,618 |
<p>I have a data file in which each participant is tested many times in several blocks. The data is formatted so that each trial contains a participant id, a block number and a score. What I want to do is group the data by participant and block, then rank the scores for each group, so I can use the top 50%.</p>
<p>For... | 69,943 |
<p>I have three different physiological variables--heart rate, respiratory rate and blood oxygen saturation, each as a time series. I am trying to study the interaction between the variables as they progress towards a particular defined point in time. I tried the use of a Vector Autoregressive (VAR) model but unfortuna... | 69,944 |
<p>How can I test the fairness of a twenty sided die (d20)? Obviously I would be comparing the distribution of values against a uniform distribution. I vaguely remember using a Chi-square test in college. How can I apply this to see if a die is fair?</p> | 49,607 |
<p>Hello data analyst community. I have the following problem:</p>
<p>Given a set of n units and a timeline in days. A unit may be active at a certain day to a certain degree (in range from 0.0 to 1.0). A desirable outcome is that if a unit is active, it should be active for a series of consecutive days (or at maximum... | 995 |
<p>I have a 2 dim matrix, and I want to know e.g. all the higher values are in the upper left corner. I can't just project it into R^3 and use a standard clustering algorithm because I don't want to consider the value as a dimension by itself. </p>
<p>Is there an algorithm I can use for this?</p>
<p>EDIT:</p>
<p>To ... | 40,976 |
<p>Is it possible to use exploratory factor analysis to extract four factors, and then combine these four factors (i.e. the factor scores for each observation) into a composite scale?</p> | 30,623 |
<p>I am using the <code>naivebayes</code> function of the <a href="http://cran.r-project.org/web/packages/e1071/index.html" rel="nofollow">e1071</a> library. Some example commands are:</p>
<pre><code>model = naiveBayes(Species ~ ., data = iris)
pred = predict(model, iris[,])
</code></pre>
<p>My question is: how can I... | 49,747 |
<p>Is it true that if
$$ 0 \leq x_n \leq y_n \xrightarrow{p} 0,$$
then
$$x_n \xrightarrow{p} 0?$$
If this is true, I would be very grateful if you could give me some references where I can find the proof.</p> | 69,945 |
<p>I am comparing two groups of mutants each of which can have only one out of 21 different phenotypes. I would like to see whether distribution of these outcomes is similar between two groups. I found an <a href="http://www.fon.hum.uva.nl/Service/Statistics/EqualDistribX2.html">online test</a>
that calculates the "C... | 69,946 |
<p>After performing a factor analysis and grouping a set of 20+ questions into 3 different factors, we can then calculate a mean, std dev etc for each of these sets of questions or in other words, per grouped factor.</p>
<p>Which test should be used to determine if there are significant differences between the means o... | 69,947 |
<p>In Libre Office Calc, the <code>rand()</code> function is available, which chooses a random value between 0 and 1 from a uniform distribution. I'm a bit rusty on my probability, so when I saw the following behaviour, I was puzzled: </p>
<p><code>A</code> = 200x1 column of <code>rand()^2</code></p>
<p><code>B</code... | 69,948 |
<p>My research question is whether aptitude tests are a good indicator on how students will perform on course exams. I have already performed an analysis on total exam score compared with total aptitude score. </p>
<p>I am now wondering whether getting a certain question on the test right or wrong is related to how th... | 69,949 |
<p>I am running a CFA and getting good fit indices (CFI = .99, RMSEA = .01) for a uni-dimensional scale. However, when I test for internal consistency, I get poor Cronbach alphas (alpha = .6). I have tried everything from removing outliers, to dropping items and still end up with the same problem. I am wondering if the... | 30,631 |
<p>I have got few questions about VECM and cointegration test.</p>
<p>Basically I conducted a cointegration test on two time series (spot vs forward price) by using the Johansen procedure. The results suggest the presence of a cointegrating relationship between the two prices, with the test statistic significant at 1,... | 69,950 |
<p>The UN has a convention against corruption (UNCAC) that has been signed by some 140 countries and ratified by most (<a href="http://www.unodc.org/unodc/en/treaties/CAC/signatories.html" rel="nofollow">link</a>).</p>
<p>Transparency International publishes an annual report on corruption. They have data for most coun... | 69,951 |
<p>Does anyone have reference to a summary of run-time analyses for common machine learning algorithms (different flavors of NN, SVMs, etc)?</p> | 40,991 |
<p>For the following popular data mining methods:
SVM, neural network, logistic regression, random forest, classification tree, Naïve Bayes classifier, regression; </p>
<ul>
<li>How to compare them in terms of their respective advantage, disadvantage, limitation of application, performance, etc? </li>
<li>What are th... | 30,633 |
<p>I have a large set of data sets. For instance, it has 30000 data points, which are identified as $1, 2, 3,\dots, 30000$. For notational purposes, $D(i)$ represents the data value for a point identified as $i$. These data points have the following localized pattern,
For a given integer value $k$, $D(3k+1) < D(3k... | 762 |
<p>I have 3 independent variables A, B, C and want to run a multiple linear regression to predict Y. After studying the correlations between:</p>
<p>1) A, Y<br/>
2) B, Y<br/>
3) A/B, Y<br/>
4) (A-B)/(A+B), Y<br/></p>
<p>It turns out that 4) has the highest correlation than all other cases by at least > 0.10. Both ... | 40,995 |
<p>Does the following corresponds to an existing process?</p>
<p>N subjects are subjected to m test items. 2 between-subject factors are manipulated with 2 modalities each. An ANOVA reveals that one of the factors is significant. </p>
<p>Does it make sense to run an "item" analysis for the significant factor? This an... | 69,952 |
<p>I have this mixture distribution</p>
<p>$f(x) =w \cdot \mathcal{LN}(\mu_1,\sigma) + (1-w)\cdot \mathcal{LN}(\mu_2,\sigma) $</p>
<p>where $\mathcal{LN}(\mu,\sigma)$ is a lognormal distribution.</p>
<p>I now have $j$ random variables</p>
<p>$ Y^{(m)} = \sum_{i=0}^n X_i $ where all $X_i$ are distributed according t... | 69,953 |
<p>Suppose I would like to model the light-bulb preference of respondents.
I would like to ask their preferences between existing bulbs on the market. And when you choose a bulb in a shop you usually see a package with many information gathered togheter such as: </p>
<ul>
<li>technology (halo, fluo, led) </li>
<li>pr... | 69,954 |
<p>According to the dataset <a href="http://fimi.ua.ac.be/data/retail.pdf" rel="nofollow">specification</a> each line of the <a href="http://fimi.ua.ac.be/data/retail.dat.gz" rel="nofollow">text file</a> is to represent an individual receipt. Each column (6 in total) represents: date, receipt no, item no, quantity, pri... | 69,955 |
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