October 1, 2006

BIO656: MULTI-LEVEL STATISTICAL MODELS

An introduction to WinBugs, Part I

About WinBugs: WinBugs is the windows-based version of Bayesian Inference Using Gibbs Sampling (BUGS), a Bayesian analysis software that uses a technique called Markov Chain Monte Carlo (MCMC) to fit statistical models. WinBugs can be used in statistical problems as simple as estimating means and variances or as complicated as fitting multilevel models. Don’t be nervous! We will tell you all about using WinBugs in lab. For now, let’s concentrate on obtaining WinBugs and navigating the website. You will impress your friends and colleagues with your MCMC skills soon enough J!

How to Obtain WinBugs (it’s free!)

1. Open your favorite web browser, and go to the BUGS website:

http://www.mrc-bsu.cam.ac.uk/bugs/

2. Click on the ‘WinBUGS’ link (4^th link down on the left), and read the page.

3. Click on the ‘Obtaining the File’ link or scroll down to the ‘Obtaining the File’ section.

4. Click on ‘WinBUGS14.exe’ to save to your computer.

5. Choose the folder to which you would like the file to be saved. I created a TEMP folder in my C:\ directory, and saved the file to C:\TEMP.

6. After downloading the file, double click on the file to start the installation wizard. Note that you can control where the program is saved, but we recommend using the default folder, which is “C:\ Program Files”.

7. Now you have WinBUGS, but only a restricted version. In order to remove the restrictions, you must obtain a key. In order to obtain the key, you must fill out a registration form. To do this, go to:

http://www.mrc-bsu.cam.ac.uk/bugs/winbugs/contents.shtml#obtain,

and click on ‘Registration Form’.

8. Fill out the registration form and submit.

9. Check your email to obtain the code and follow the directions in the email.

10. Now you have unrestricted WinBUGS!

More Goodies from the BUGS Website:

1. WinBUGS - The Movie, an online demo of WinBUGS, is available at

http://www.mrc-bsu.cam.ac.uk/bugs/winbugs/contents.shtml#whatget

2. The WinBUGS user manual is available at

http://www.mrc-bsu.cam.ac.uk/bugs/winbugs/contents.shtml#features

3. Examples are available at

http://www.mrc-bsu.cam.ac.uk/bugs/winbugs/examples.shtml

4. FAQ are at: http://www.mrc-bsu.cam.ac.uk/bugs/faqs/contents.shtml

The above is not an exhaustive list of resources, but will help you get started (hopefully) without overwhelming you. Stay tuned for some simple examples using WinBUGS!