Using G power, please help me with what to do/how to interpret the results.

First of all, I looked at two independent groups (group 1, N = 9; group 2, N = 25). I found that group 1 had significantly higher testosterone levels (hormone levels ln transformed) than group 2 (independent samples t-test, p = 0.015).

So, how do I do power analysis on this variable in G power?

Go to:

Test family: t-tests

Statistical test: Means: Difference between two independent means (two groups)

Type of power analysis: Post hoc: Compute achieved power - given alpha, sample size, and effect size.

Right?

Input:

tails: 2

Effect size d: ??? <----what do i put here?

alpha error prob = .05

sample size group 1 = 9

sample size group 2 = 25

What do I put for effect size? .8? Also, how would I interpret the results, and report them?

Say power (1-beta err prob) comes out to 0.5144291, what does that actually mean, and how do I report that in my manuscript?

Thank you for the help ahead of time. Bear with me, I've never taken a stats course and am pretty bad at this math stuff.