In case of adverse drug reaction study, there is no control group and only the patients use the drug. After using the drug, some patients show some adverse drug reactions and others do not show these. We have now he genotyping data, patient subgroups depending on the different adverse drug reactions and odds ratio. Due to the division of the patients in different subgroups, the number of patients in each group is not very large. Now how can I prove that my sample size meets the 80% statistical power? Is there any special method of power calculation for the Pharmacogenomics adverse drug reaction?
Hi Mohammad, for statistical power, sample size e.t.c you can use Gpower statistical software. You can get it from the link below it is free and has tutorials. It's actually user friendly.
http://www.gpower.hhu.de/
You can estimate the sample size according to your information about the population which the sample will be taken from it :
Sample size from finite population can be estimate by :
n= N / ( 1+ N * e^2 )
and from infinite population by :
n= ( Z^2 * S^2) / E^2
where : Z ( 1.96 for 0.05 and 2.58 for 0.01 )
S = standard deviation from previous studies or pilot study
E = significant level
Also, you can use software to calculate sample size ( SPSS , Minitab , Gpower )
The key component to estimate sample size ( when we fixed the other ) is variance of the trait , when the study include many traits , we depend on the trait of higher variance which give us estimation sufficient sample size suitable for other traits.
I hope that be useful for you
Hi, there is no specific program for pharmacogenetics. However, you can use specific software such us QUANTO (http://biostats.usc.edu/software), specially designed to estimate statistical power and sample size in genetic studies.
You can also use PGA: Power for Genetic Association Analyses (PGA) to verify your hypothesis, to use in the worst condition for minor allele frequency and variant influence it is always suitable
Dr. David Flockhart of Indiana University has published a lot of work in this area. I suggest a literature search of his publications.
to do power analysis to estimate your sample size, you have to write your hypothesis, and based on that you decide what statistical test you will use. It should be one of the inferential statistics. so you need to determine the following: alpha {standard to be .05}, power [standard to be .80], effect size {small, moderate, or large, each test has its own value, you can find these values in the net}. Then download free programs to calculate the sample size such as G. power.
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