= Sample size for a one sample t-test =

This [[attachment:onesamp.xls|spreadsheet]] computes the total sample size for a one sample t-test with given power. 

This can also be done using this [[http://www.stat.ubc.ca/~rollin/stats/ssize/n1.html|on-line calculator.]] Both these programs use the more liberal normal quantiles as opposed to t quantiles for sample size evaluation.

The web calculator [[http://www.sample-size.net/sample-size-study-paired-t-test/ | here]] computes the number of subjects for a paired t-test using the formula on page 39 of
 
Kraemer HC and Thiemann S (1987) How many subjects? Statistical power analysis in research.  Sage.:London. (There should be a copy of this book in the CBU library).

The formula is:
N for paired t-test = (1.96+0.842)^2 ^ x (difference in paired means / sd of the DIFFERENCE in the means)^2 ^ for 80% power, two-tailed type I error of 5%.