Power {epiDisplay}

Power calculation for two sample means and proportions

Description

Calculation of power given the results from a study

Usage

power.for.2p(p1, p2, n1, n2, alpha = 0.05) 
power.for.2means(mu1, mu2, n1, n2, sd1, sd2, alpha = 0.05) 

Arguments

p1, p2

probabilities of the two samples

n1, n2

sample sizes of the two samples

alpha

significance level

mu1, mu2

means of the two samples

sd1, sd2

standard deviations of the two samples

Details

These two functions compute the power of a study from the given arguments

Author(s)

Virasakdi Chongsuvivatwong [e-mail]

See Also

'n.for.2means', 'n.for.2p'

Examples

# Suppose, in the example found in 'help(n.for.2p)', 
# given the two proportions are .8 and .6 and the sample size 
# for each group is 60.

power.for.2p(p1=.8, p2=.6, n1=60, n2=60) # 59 percent

# If the means of a continuous outcome variable in the same 
# two groups were 50 and 60 units and the standard deviations were 30 
# and 35 units, then the power to detect a statistical significance 
# would be

power.for.2means(mu1=50, mu2=60, sd1=30, sd2=35, n1=60, n2=60) 
# 39 percent. Note the graphic display