FPL Statistics Group

Power Calculations for a General Linear Model

Welcome to the power portion of the GLM program. Draft documentation for the program is available via this link.

As currently written this program can handle at most 400 rows and 75 columns in the design matrix. If this is insufficient for your purposes, please contact Steve Verrill at 608-231-9375 or at sverrill@fs.fed.us.

Before proceeding with the power calculations you must provide design and hypothesis matrix files. If you have already done so, you may proceed with the form below.

What is the name of the design matrix file?

What is the name of the hypothesis matrix file?

How many rows are there in the design matrix?
(400 or fewer)

How many columns are there in the design matrix?
(75 or fewer)

How many rows are there in the hypothesis matrix? (What is q?)
(75 or fewer)

What are the values of the c'bs under the alternative hypothesis? (You must provide q values separated by spaces.)

How many sigmas do you want in the power table?

What are the sigma values?

What power do you wish to achieve?
(e.g., .90 if you want to have a 90% chance of obtaining a statistically significant result given that the difference actually exists. Desired power values must lie between 0 and 1.)

What name do you want for your results file?

The name should be unique to you to prevent the file from being accidentally overwritten by another user.

Since you will see an html document that presents the results as soon as you execute the program, you may not want an ascii copy. However, we do provide this option.

The ascii file will be written in the pub/data anonymous ftp directory. If a file by the same name already exists in the directory, the new results will be appended to the existing file. Check the anonymous ftp link for directions about retrieving the file.

If ftp does not run on your machine, e-mail me at sverrill@fs.fed.us and ask me to e-mail the results file to you. Do this quickly as the pub/data directory is cleaned weekly.

For further information, please contact Steve Verrill at sverrill@fs.fed.us or 608-231-9375.

Last modified on 1/14/2000.

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