# All Questions

0answers
110 views

0answers
171 views

### Do I apply delta method correctly?

I'm no mathematician, so please consider the whole explanation as a subject to criticism and optimization. I'm trying to build a model and calculate an estimate of error variance for the following ...
2answers
606 views

### Should a mixed effects model be used?

This post provides an excellent example of the inner workings of a mixed effects model: http://emhart.github.com/blog/2012/11/16/making-sense-of-random-effects/ In a hypothetical study, I have ...
0answers
51 views

### How to read the table to get cumulative relative frequencies?

there is a question i can not answer. Suppose the numbers in the following random number table correspond to people arriving for work at a large factory. Let 0,1,and 2 be smokers and 3-9 be ...
1answer
371 views

### Comparison between MDL and BIC

I'm currently studying Hidden Markov Models. There's a set of observations from which I need to determine the optimal number of states. After having found the maximum likelihood using Baum-Welch, I ...
2answers
1k views

### Maximum likelihood equivalent to maximum a posterior estimation

When is maximum a posterior (MAP) estimation equivalent to maximum-likelihood (ML) estimation?
1answer
347 views

### QQ plot is consistent with normality when subgroups are non-normal

I have read that for a one way ANOVA, you should check that the model residuals are normally distributed. If the variance of each group is homogeneous then this implies that the residuals with each ...
0answers
162 views

### Classification of states in Markov Chain

Question Consider the following transition matrix: ...
2answers
610 views

### Is a larger beta weight a better predictor than a high t-statistic?

Say there are two variables. Variable A has a higher $\beta$ weight than variable B but variable B has a higher t-statistic than variable A. Can either of these measurements, standardized $\beta$ or ...
1answer
2k views

### How does one define own intercept in regression model in R?

My case is that I have one continuous DV variable and two categorical IVs containing 11 and 12 different levels (YEAR & MONTH) form 1998 to 2008. Until now I have experimented a lot with ...
1answer
133 views

### Dumb Bayes theorem question

What's the difference between "probability of H given E" as calculated by Bayes theorem and the "positive predictive value" of E?
3answers
626 views

### Which test(s) for analyzing yes-no answers for control vs treated conditions

To keep it simple, I have sets of data in which I have a control and a treated sample. The data I obtain is "yes" or "no" (0 or 1) for a particular behaviour. I have 150 data points for each condition ...
1answer
336 views

### Training Hidden Markov Models for multiple input observations

I'm working with Hidden Markov Models and I have a dataset composed by independent phrases, where each word is an observation. Hence, the best way to adjust my parameters (via Baum-Welch algorithm) is ...
1answer
803 views

### Estimate beta binomial distribution

I have a dataset as follows: ni-xi 76 48 38 19 20 14 26 29 39 45 38 36 32 34 26 21 23 12 24 18 14 61 35 21 32 20 89 30 34 35 xi 0 0 16 26 1 8 23 19 24 16 16 19 0 0 0 6 8 3 5 9 5 0 34 ...
1answer
55 views

### ANOVA using day numbers

I am looking at differences in dates of maximum counts of geese at 3 sites in the UK. My data look like these created in R: ...
2answers
336 views

### Simulating ordinal variables using fitted probit models

I have fitted a probit model for an ordinal response and a number of predictors, using polr function in R. Now I want to use this fitted model in order to sample from the conditional distribution of ...
2answers
216 views

### How to combine p values? [closed]

I have three datasets A, B and C. A and C can construct a contingency table, and I can get a p value (pValue1) with Fisher's exact test. B and C can construct another contingency table, and I can get ...
0answers
551 views

### How is mean date calculated?

I was surprised to discover yesterday that various summary statistics can be calculated on dates. Googling has found lots on syntax required to calculate summary statistics on dates, but very little ...
2answers
254 views

### Multivariate Weighted Linear Regression

Very simple. I am looking for a package that does Multivariate Linear Regression with weights on the observations. Does anyone know of a package that does this? I am shocked that I have not been ...
1answer
239 views

### Standard deviation of weighted sums of random distributions with weights random but fixed

Let $a,b,c,d$ be independent normally distributed random variables. I'm aware that the following distributions: $$c a + d b$$ $$(c+d)a$$ both have the same standard deviation ($=\sqrt{2}$ if ...
1answer
109 views

### Explanation of a step in derivation of residuals for R lm diagnostic?

I'm reading Faraway's book (http://cran.r-project.org/doc/contrib/Faraway-PRA.pdf) to try to understand R's lm diagnostic plots. On page 72 of the book is this: I have been trying to understand a ...
1answer
576 views

### using a number of variables (dummy) in mixed model analysis in R

I have following type of data: ...
1answer
271 views

### Poisson regression - dealing with widely different population sizes

I have a dataset of counts (responses to a marketing campaign), collected at the zipcode level. I am trying to use a poisson regression to determine underlying response rate of each zipcode. How do ...
1answer
105 views

### Relative efficiency of matching versus adjustment to handle confounding effects in highly disproportionate populations

I am reviewing a paper where the authors compare cancer outcomes (binary) between two groups, one having a small sample size of 200 and the other having over 55,000. The authors then claim that, due ...
0answers
223 views

### How to pick a good threshold for multimodal histograms

I am trying to do multi-modal detection in a vote map (histogram) however, side lobes obviously cause some false peaks. So using mean shift will not do as it will find all of the local maxima. So I ...
2answers
904 views

### Sampling from the normal-gamma distribution in R

Does anyone know of a way to sample from the normal-gamma bivariate distribution or the normal-inverse-gamma bivariate distribution in R? I could create the distribution myself as a function, but ...
0answers
519 views

### Providing the actual measured error instead of weights to the lm function in R (or similar linear fit function)

Is there any way to use the linear fit function or R with my own errors instead of the value weights? That is, I have a physical experiment in which we know the errors for each point, for instance: ...
1answer
755 views

### What does intercept actually mean in a simple linear model?

Given y = a + b*x, does "a" represent simply an intercept or mean y? For y = a + b*ln(x), is there a need to interpret the intercept "a?"
1answer
812 views

### Formula to generate Critical t-values for t-test (instead of using a look-up array)

I am searching for the formula that will generate the critical values in a t-test instead of using a static critical value table. I am programming in Java and not R so the qt() function is not what ...
1answer
137 views

### Random geometric graph connectivity

Given N random points uniformly distributed in the unit square, and a distance d, i can generate a matrix in the following format: ...
1answer
497 views

### Compute the variance of parameter estimates given limited number of samples

I'd like to infer the variance of estimated parameter $\hat\theta$ of the density function of $f(x;\theta)$ given only a limited number of samples $X_1,\cdots,X_n$. Bootstrapping doesn't perform well ...
1answer
273 views

### Unbalanced Haar Wavelets and R package unbalhaar

I have found the article by Fryzlewicz (2007) and his R package unbalhaar. I do not understand well the outputs of his functions and in particular of the ...
1answer
82 views

1answer
865 views

### Checking confidence intervals on user defined contrast (one-way ANOVA)

Hi is anyone able to help - I am doing this all in R Code: I have run one way analysis on some data and set up 2 contrasts (Liberarts-Finearts and also Engineering-science). I now need to calculate ...

15 30 50 per page