## Solved – How to combine data from 2 separate experiments

I am a scientist and by no means a statistician. I have, I think, a very basic question for you all. I have performed the same experiment twice (analyzing levels of a certain protein) and am comparing levels in untreated vs treated animals. I performed a t-test with welch correction (because there was significant variance). … Read more

## Solved – Downsides of inverse Wishart prior in hierarchical models

I am working with a Bayesian hierarchical model that has a number of parameters for each experimental unit (6 parameters). I really do not know all that much about them a-priori, but it is quite plausible that they could somehow be correlated. Thus, I was considering a multivariate normal distribution for the random effects with … Read more

## Solved – Is correlation between parameters a problem when fitting a Bayesian model using MCMC

Assuming some Bayesian model, for example: \$\$y sim N(Xbeta, sigma)\$\$ where this model has: Response vector: \$\$ y = pmatrix{y_{1} \ y_{2} \ vdots \ y_{n}} \$\$ Predictor matrix: \$\$ pmatrix{ x_{11} & x_{12} & ldots & x_{1p} \ x_{21} & x_{22} & ldots & x_{2p} \ vdots & vdots & ddots & vdots \ … Read more

## Solved – What math/stats knowledge does learning Bayesian probability require

I study undergraduate "pure" math and philosophy. I know that a number of philosophers use Bayesian probability to augment their epistemic logic. My school teaches Bayesian probability as a brief part of a fourth year class. Enrolling in it requires completing a series of stats classes that are outside of my path. However, for a … Read more

## Solved – Exponential Distribution – Rate – Bayesian Prior

I have gone through WinBugs documentation (for example, http://www.mrc-bsu.cam.ac.uk/bugs/thebugsbook/examples/html/Chapter-11-Specialised/Example-11_7_2-leukaemia.html). And also through this book (http://www.amazon.ca/Bayesian-Survival-Analysis-Joseph-Ibrahim/dp/0387952772). Both use a gamma distribution prior for the rate (lambda) for the exponential distribution. They alternate between Gamma(0.01,0.01) and Gamma(0.001,0.001). I would like to use a non-informative prior…. but I don't think this is it? Could someone explain whether this … Read more

## Solved – Exponential Distribution – Rate – Bayesian Prior

I have gone through WinBugs documentation (for example, http://www.mrc-bsu.cam.ac.uk/bugs/thebugsbook/examples/html/Chapter-11-Specialised/Example-11_7_2-leukaemia.html). And also through this book (http://www.amazon.ca/Bayesian-Survival-Analysis-Joseph-Ibrahim/dp/0387952772). Both use a gamma distribution prior for the rate (lambda) for the exponential distribution. They alternate between Gamma(0.01,0.01) and Gamma(0.001,0.001). I would like to use a non-informative prior…. but I don't think this is it? Could someone explain whether this … Read more

## Solved – Confusion Matrix to Calculate Probability

I was asked a relatively simple problem and was curious as to how to solve. Say I had a bomb detector at the airport, and it is 99.99% correct. That being, when the detector goes off or does not go off, it is correct 99.99% of the time. And in the population, 1/10,000 people actually … Read more

## Solved – Confusion Matrix to Calculate Probability

I was asked a relatively simple problem and was curious as to how to solve. Say I had a bomb detector at the airport, and it is 99.99% correct. That being, when the detector goes off or does not go off, it is correct 99.99% of the time. And in the population, 1/10,000 people actually … Read more

## Solved – Bayesian vs Frequentist: practical difference w.r.t. machine learning

I know that Bayesian and frequentist approaches differ in their definition of probability. Practically, in machine learning a model is a formula with tunable parameters. Then the difference between Bayesian and frequentist is: That the parameters are assumed to be fixed numbers in frequentist setting and the parameters have their own distributions in the Bayesian … Read more

## Solved – How to identify this trap error in WinBUGS

I am currently working on my thesis and interested in estimating a Weibull conditional Hazard Frailty Model for recurrent event data using WinBUGS. I wrote the model but when am trying to use it with the following script it hangs unexpectedly. It returns a messages titled "undefined real result". What am I doing wrong? Also, … Read more