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7
votes
2answers
322 views

Temporal trend visualizations for regions

I try to reproduce a plot which I found in a publication (Mayor-Fernández et al 2012) showing unemployment rates across time for several regions. It combines a heatmap (?), a time series plot (lower ...
5
votes
1answer
536 views

Sample size for multiple regression: How much more data do I need?

I'm trying to test a prediction from a computational model with a biological experiment. The model predicts a linear dependence between cell size and asymmetry. I performed an experiment that is ...
5
votes
2answers
6k views

Confusion regarding correlation and mse

I have a dataset containing three variables. I have this confusion, low mse means higher correlation isn't it? Now when I calculate the mse for variable two and three where the third variable is my ...
7
votes
1answer
135 views

Convergence of MCMC for ill-behaved functions

We are doing MCMC sampling over an n-dimensional space with a population of MCMCs. The goal is to have them stop when they approximately converge. The problem is that the convergence, which is so ...
7
votes
2answers
15k views

Whether to use original or reverse coded items in factor analysis?

I am currently analyzing data from a 34-item Likert scale. I already recoded the negatively stated variables in SPSS as different variables. I'm about to do a factor analysis. Should I use the ...
6
votes
1answer
257 views

To aggregate and lose resolution OR not to aggregate and suffer with correlated binary data?

I have data from an experiment in which each participant provides a binary response to each presented stimulus, which is either correct (1) or incorrect (0). There are 4 different stimulus types, ...
4
votes
1answer
204 views

Testing whether there is a difference between two groups who were asked the same set of questions

I asked two groups of individuals (80 males and 10 females) fill out a questionnaire asking them their attitude towards a series of political variables. Every individual had to answered a set of 16 ...
8
votes
4answers
37k views

Which result to choose when Kruskal-Wallis and Mann-Whitney seem to return contradicting results?

I have these groups where the values are responses to a 10-point Likert item: g1 <- c(10,9,10,9,10,8,9) g2 <- c(4,9,4,9,8,8,8) g3 <- c(9,7,9,4,8,9,10) ...
8
votes
1answer
4k views

Confidence intervals around a centroid with modified Gower similarity

I would like to obtain 95% confidence intervals for centroids based on Gower similarity between some mulivariate samples (community data from sediment cores). I have so far used the ...
2
votes
2answers
2k views

What level of measurement is a factor score?

After doing a factor analysis, I decide to use that factor to test a hypothesis. However, I am not sure what data type of the Factor score the is (i.e., nominal , scale, etc.). Can I do a t-test or ...
8
votes
1answer
24k views

How does ties.method argument of R's rank function work?

I am using rank(a, ties.method="max") to rank a. But I am not quite sure what does ties.method="max" do. Can you please help?
4
votes
0answers
148 views

Does anyone know how this visualization was made? [closed]

I've been tasked with implementing a visualization something like this one from the New York Times: http://www.nytimes.com/interactive/2012/08/05/sports/olympics/the-100-meter-dash-one-race-every-...
5
votes
2answers
278 views

What test should I choose if I want to see if two groups are different from each other in many categories?

I am currently analysing data of a big webshop with over 31,000 vendors selling goods, i.e. each vendor is selling items over the webshop. The cool thing is that we know the gender of these vendors (=...
2
votes
0answers
2k views

Differences between Stata & SPSS in multiple regression outcomes

I'm a graduate student working on a thesis whose aim is to test complementarity between 2 practices (CI and INNO, according to theory of supermodularity). To do so, I calculated two new variables (...
5
votes
2answers
2k views

How to know the stochastic gradient descent is converging when the objective function is expensive to compute

How can I know if the stochastic gradient descent algorithm is converging. I cannot plot my objective function and take its average for lets say every 1000 iterations to see the trend. My objective ...
2
votes
1answer
762 views

Shouldn't the beta estimates always be the same using lm and lmer?

Can anyone tell me under what conditions the beta estimates differ between lm and lmer with a random intercept? I came across a situation where the fixed effect differed considerably. I thought the ...
3
votes
0answers
51 views

Can a different indexing approach improve the relevance and efficiency of search engine results?

I am creating a search engine, with the corpus consisting of websites crawled through a webcrawler (Apache Nutch). I need the query searches to be both fast and relevant. So far, I have been trying to ...
4
votes
2answers
155 views

What are possible reasons for differences in numerical output from the same procedures performed in different statistical packages?

My colleague and I do the exactly same thing with the exactly same data and get different results. He uses Stata, I use R. We both use 32-bit Windows machines. Are there any possible explanations ...
2
votes
0answers
106 views

How to build a predictive model using sound (frequency and amplitude) as the input

I'm working on a medical research project where we're looking at the changing resonances in femur bones during hip replacement operations. Some surgeons use the increasing pitch of the bone resonance ...
14
votes
3answers
5k views

Concepts behind fixed/random effects models

Can someone help me to understand fixed/random effect models? You may either explain in your own way if you have digested these concepts or direct me to the resource (book, notes, website) with ...
2
votes
1answer
96 views

Resources for developing prognostic index-scores

I am looking for online resources or books explaining how to develop prognostic indexes-scores step by step. I am mainly wondering about model validation and transformation of regression coefficients ...
5
votes
1answer
992 views

Double exponential smoothing in multivariate multilevel panel regression

I would like to use double exponential smoothing to predict prevalence rates of care dependency in Austrian federal states. My data is very detailed, thus I would like to make use of that in order ...
5
votes
1answer
683 views

At what VIF level should you switch from OLS to ridge-regression?

Regarding multicollinearity, is it recommended to use ridge-regression if you have some covariates with VIF values around 10 in the OLS model? What would be the best VIF level to use to decide ...
1
vote
0answers
78 views

Dirichlet density with just one x value and one alpha parameter

Does it make any sense to apply the Dirichlet density function to only one x value and therefore one alpha parameter? (this would be the result of some bin merging) I'm asking because it appears ...
1
vote
1answer
191 views

Find the mean and variance of $U_1 + U_2$

Let $Y_1, Y_2, Y_3$ be i.i.d continuous random variables. For $i = 1, 2$ define $U_i$ as $U_i=1$ if $Y_{i+1} > Y_i,$ $=0$ ,otherwise Find the mean and variance of $U_1 + U_2$ I can't find the ...
9
votes
4answers
3k views

Model selection and model performance in logistic regression

I have a question about model selection and model performance in logistic regression. I have three models that are based on three different hypotheses. The first two models (lets name them z and x) ...
1
vote
1answer
157 views

Can I compare correlations even though one is NOT significant?

I have 2 groups and 2 correlation coefficients that I would like to compare using Fisher's transformation. Unfortunately, one of these coefficents is not significant, so not different from zero. Can ...
0
votes
1answer
2k views

Analyzing repeated measures ANOVA with two groups

I have a data set that looks like this: ...
9
votes
2answers
369 views

Dynamically adjusting NN architecture: inventing the unnecessary?

I am starting out on my PhD journey, and the ultimate goal that I set before myself is developing ANNs that would monitor the environment they work in and dynamically adjust their architecture to the ...
3
votes
0answers
643 views

How to find a breakpoint for each ID in a linear regression model with R?

I have some repeated measures with 196 individuals and some of my regressions have a plateau. So I want to characterize this with an eventual breakpoint for each ID. Example: subset of my personal ...
2
votes
3answers
225 views

Evaluating model performance without validation data

I've found myself in a situation where I have been given a model that has been developed from what I believe to be the "this seems right" approach. The model in question is very complex but it has no ...
1
vote
0answers
26 views

dirichlet density function returning values > 1.0 [duplicate]

Possible Duplicate: Probability distribution value exceeding 1 is OK? I'm comparing results given by this implementation and that from the gtool library in R, of the Dirichlet density function. ...
5
votes
1answer
4k views

Subsample bootstrapping

I have been working on the uncertainty associated with a quantity calculated from a Monte Carlo project. Normally I would use the bootstrap method by resampling with replacement, for a couple of ...
1
vote
1answer
508 views

Dense Data Compression (Delta Encoding?)

Let $X $ be a dense integer set such that its elements are closely knit in value. For instance: 1 1 1 1 2 2 2 2 2 3 3 5 5 6 6 6 6 6 7 7 7 7 8 8 8 8 8 8 ... I am ...
4
votes
0answers
59 views

Estimating a time frame for interventions or judging the extent to which events become “determined” as time goes on

In certain arenas, it's valuable to be able to intervene early on to prevent problems from getting worse, because after a certain point there's not much you can do. Two examples might be public health ...
0
votes
2answers
282 views

Compute $\mathrm{Cov}(\sum_{i=1}^NX_i,\sum_{i=1}^NY_i)$

Let $X_1,X_2,\dots$ be i.i.d. Bernoulli random variables with parameter $\frac{1}{4}$. Let $Y_1,Y_2, \dots $ be another sequence of i.i.d. Bernoulli random variables with parameter $\frac{3}{4}$. And ...
7
votes
1answer
245 views

Is Ye Shiwen's 400m IM performance in Olympics “anomalous” statistically?

The 16-year-old Chinese swimmer Ye Shiwen swam more than 5 seconds faster than her personal best in women's 400m individual medley in London 2012 Olympics, winning her a gold. Her performance received ...
2
votes
0answers
669 views

Group-level correlation effect

I am measuring two continuous variables ($X,Y$) for 21 subjects. $X$ and $Y$ have 216 data points each (per subject). I would like to see if $X$ and $Y$ are correlated at the group level. I can think ...
2
votes
3answers
3k views

How to build a regression model with just 5 datapoints with 5 or more variables?

I am attempting to build a simple multiple regression in order to estimate the value of a home. The 5 datapoints are 5 comparable home sales (similar in size, lot, location, # of bedrooms, etc...). ...
4
votes
0answers
66 views

How to define and model consumption bundles?

Imagine an a la carte buffet with n different rooms. On entering the buffet you pick a room (let's say American, Mexican or Italian food) where you stay for the duration of your visit. Once in a room,...
4
votes
1answer
2k views

Modelling a binary response variable with a binary explanatory variable

I'm modeling (using GLM) one binary explanatory variable against a binary response variable. The output looks ok to me, but I'm a biologist with a basic knowledge of stats, I just wanted to ask if ...
6
votes
4answers
14k views

How to perform pooled cross-sectional time series analysis?

For 86 companies and for 103 days, I have collected (i) tweets (variable hbVol) about each company and (ii) pageviews for the corporate wikipedia page (...
4
votes
1answer
131 views

Inferring multiple ratios and binomial proportions with missing data

I have a number of studies describing families tested for a genetic condition. For each study the following data are described: $n_p$, number of probands (the proband is the first person in a family ...
14
votes
1answer
9k views

Is there an optimal bandwidth for a kernel density estimator of derivatives?

I need to estimate the density function based on a set of observations using the kernel density estimator. Based on the same set of observations, I also need to estimate the first and second ...
40
votes
1answer
7k views

How to determine significant principal components using bootstrapping or Monte Carlo approach?

I am interested in determining the number of significant patterns coming out of a Principal Component Analysis (PCA) or Empirical Orthogonal Function (EOF) Analysis. I am particularly interested in ...
1
vote
1answer
143 views

Statistical test for a gradually self-improving suggestion system

I built a suggestion system, which provides a list of candidate items to users. As users choose some items from the suggested list, the system remembers those choices, and the next time the system ...
4
votes
2answers
587 views

How do you identify the variables that separate several groups?

I don't have much background on statistics. I am working on multivariate morphometrics of a sample of frogs. I have a data matrix of 19 variables (continuous characteristics) for around 250 samples. ...
2
votes
0answers
814 views

Sample session for analysis of conjoint data in R

While I have successfully used R for Cluster Analysis and Correspondence Analysis, I'm new to the use of R-project for Choice-Based Conjoint. Per recommendations in this post, I'm looking at the ...
0
votes
1answer
154 views

Why can't a Self Organizing Map to recognize handwriting train to acceptable error rate when number of samples is greater than output neurons?

I have a simple Self organizing map that I have been working on. It has an output neuron for all 26 letters, and when I provide it with 26 samples (one for each letter) it quickly is trained to an ...
12
votes
1answer
2k views

The relationship between the number of support vectors and the number of features

I ran an SVM against a given data set, and made the following observation: If I change the number of features for building the classifier, the number of resulting support vectors will also be changed. ...

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