UKC

One factor within subject experiment.
I want to do a sample size calculation for 2 levels versus 4 levels of the independent variable.
Say for 80% power at p< .05 if I have that right.
I have been informed I am dealing with a repeated measures ANOVA.

Is there a formula or calculator I can access to work this out (the sample sizes for 2 level versus 4 level to show significance at that level of power) and will I need any data estimates of effect (say from previous research) or any other numbers to fit into the calculator/formula?

Thanks in advance.

In reply to koalapie:

Bump

In reply to koalapie:

Hi

I JFG "sample size calculator 4 levels repeated measures anova"

and there are a number of option but this doc explains similar using G*Power
(a free windows thing) There are also online calcs.

http://core.ecu.edu/psyc/wuenschk/MV/RM-ANOVA/Power-RM-ANOVA.doc

In reply to lithos:

Thanks! That looks like it may be exactly what I am after.

In reply to lithos:

Hi again,

The article from the document (Cohen 1992)gives a table of estimated sample sizes for 8 types of design including ANOVA.

Is running it through gpower3 better because it factors in variation of measurement apparatus?

I downloaded gpower3 and followed the instructions but the input parameters were different, will that matter? Eg there was no f squared treatment effect parameter but there was an error parameter

The gpower3 doesn't function fully on my computer, the program window doesn't fully expanded and I have the opaque pane at the bottom of the small window (like when you can't print an article directly from a PDF link but have to save it to enable printing controls) i removed and re-installed, repaired, changes resolutions but nothing worked. Any suggestions or is it just a matter of trying on a different computer?

In reply to koalapie:

G*power is very old, find an old XP computer and it may work better !

dont know the answers to the others, sorry