Can anyone here me with one biostatistics question. It is about finding the sample size from power analysis. I have the variables. Just need an assistance with the calculations.
G*power is the best, Sal Mangiafico? It surprises me to hear a useR say that! ;-)
Mostafa Elsersy, you need to provide more information. E.g., what is your study design? And what is the smallest measure of effect size that you would consider practically important, and wish to have power to detect? If you provide that kind of info, someone may be able to direct you to an online calculator that is (perhaps) easier to use than G*power. Here are a couple of such sites that come to mind:
- https://www.sealedenvelope.com/power/
- https://epitools.ausvet.com.au/samplesize
In most cases for practical purposes it is not required to use fancy software for sample size calculations. See
http://www.vanbelle.org/struts.htm
Note that we have only vague idea about the effect and the variability we should expect to base the sample size calculation on. Further, we select alpha and beta not to precisely optimize the net-win (or -loss) but rather use arbitrary, only roughly rational values. Based on full guesswork it seems really stupid to calculate a required sample size with a precision of 5 decimal digits. Getting an idea about the order of magnitude is sufficient in any practical setting, imo. Happy to hear from you why I am wrong here.
Sal Mangiafico Bruce Weaver Jochen Wilhelm I Edited the Q with full details
AH, this kind of problem :) I suggest reading the course materials and ask your instructor.
And if I remember correctly, the RG guidelines forbid asking exam questions in the forum.....
https://www.psychologie.hhu.de/arbeitsgruppen/allgemeine-psychologie-und-arbeitspsychologie/gpower
- Badges
- Science topic
- Similar topics
- Medicine
- Disease
- Infectious Diseases
- Immunization
- Vaccination