Power {epicalc}R Documentation

Power calculation for two sample means and proportions

Description

Calculation for power given the results

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 sample
n1, n2 sample sizes of the two sample
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 results

Author(s)

Virasakdi Chongsuvivatwong <cvirasak@medicine.psu.ac.th>

See Also

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

Examples

# Suppose, in the example found in 'help(n.for.2p)', 
# given the two proportions are found at .8 and .6 but 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 an continuous outcome variable in the same 
# two groups were 50 and 60 units and the sd's were 30 and 35 units, 
# then the power to detect 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

[Package epicalc version 2.5.0.3 Index]