gistfile1.r

M = 10000    # Number of sims  
power = .5   # power


## Binomial (fixed N)
N1 = rpois(M,2) + 1   ## random choice for N
X1 = rbinom(M,N1,power)  ## Perform studies
mean(X1 / N1)
sd(X1 / N1)

## Notice above that, as expected, expected prop.
## of significant studies is power

## Geometric (stop with single nonsig. result)
X2 = rgeom(M,1-power) 
N2 = X2 + 1

# show power
sum(X2) / sum(N2)

# However, expected proportion sig. is < .5 !
mean(X2 / N2)
sd(X2 / N2)

## Interestingly, the expected proportion of sig.
## studies is *less than* the power!