Hi there,
I am designing an experimental with several groups and wish to reliably determine sample size a priori for each group where I have an effect size set at 0.25 and power of 0.8.
I have a total of 16 groups where I have the following conditions (which are named this for confidentiality purposes):
Treatment A (2 levels +/-)
Treatment B (2 levels +/-)
Treatment C (2 levels +/-)
Timepoint (2 levels)
I've tried calculating sample sizes in g power and R (pwr package) and both give me different results. I am relatively new to this way of designing experiments and I wish to get as much advice as possible. Basically we want to determine whether our treatments influence our dependent variable at either time-point so should I be looking at running power calculations based on ANOVAs?
Any advice or help would be much appreciated!
Thanks in advance,
David
It is good to use the Minitab software in this study. There are good ways for you.
I have found this Utah State pdf a good guide for students in my classes. Gives a good explanation of what you are doign in power analysis and makes software recommendations with instructions
http://rgs.usu.edu/irb/wp-content/uploads/sites/12/2015/08/A_Researchers_Guide_to_Power_Analysis_USU.pdf
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