Power analysis for patient samples
Entering edit mode
16 months ago
mropri ▴ 150


I am trying to calculate power for 150 samples where 75 are going to be in one group and 75 in another. I tried using the pwr package in R to get the power where I used the following code:

pwr.anova.test(k=2, n =75, f=.1, sig.level=.05, power=NULL)

k for me equals 2 because the 150 samples are divided into two groups equally (75 each)

n which is the sample size is 75 for both groups

f is the effect size which I set to 0.1

significance level I set to 0.05

I get a number for power which is 0.23 which obviously is low. My question is, am I doing this correctly? I am new to power calculations and if someone could help me understand how to calculate power knowing the sample size or point me to a package that can correctly do this for my example, I would truly appreciate this.

RNA-seq • 543 views
Entering edit mode

I think you're doing it right. Since you only have 2 groups, you can use pwr.t.test. The default alternative hypothesis is two-sided, but if you are only looking for an increase or decrease, then you can use a one-sided alternative hypothesis. Alternatively, you can use power.t.test, but you will need to proved an estimated standard deviation.

Entering edit mode

Sounds good, thanks Jeremy for the help, really appreciate it.


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