FAQ/power/onesamp - CBU statistics Wiki

Upload page content

You can upload content for the page named below. If you change the page name, you can also upload content for another page. If the page name is empty, we derive the page name from the file name.

File to load page content from
Page name
Comment
Type the odd characters out in each group: abz2a 125t7 HhHaHh year.s 5433r21 worl3d

Revision 15 as of 2017-08-31 12:15:23

location: FAQ / power / onesamp

Sample size for a one sample t-test

This spreadsheet computes the total sample size for a one sample t-test with given power.

This can also be done using this on-line calculator. Both these programs use the more liberal normal quantiles as opposed to t quantiles for sample size evaluation.

The web calculator 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 / (difference in paired means / sd of the DIFFERENCE in the means)2 for 80% power and two-tailed type I error of 5% so

Example Using the above formula if the raw paired subject difference is 0.303 and the sd of this difference equals 0.266 then we require 7.85 / (0.303/0.266)2 = 6 subjects.