size.ci.prop2 {statpsych} | R Documentation |
Sample size for a 2-group proportion difference confidence interval
Description
Computes the sample size in each group required to estimate a difference of proportions with desired confidence interval precision in a 2-group design. Set the proportion planning values to .5 for a conservatively large sample size. Set R = 1 for equal sample sizes.
Usage
size.ci.prop2(alpha, p1, p2, w, R)
Arguments
alpha |
alpha level for 1-alpha confidence |
p1 |
planning value of proportion for group 1 |
p2 |
planning value of proportion for group 2 |
w |
desired confidence interval width |
R |
n2/n1 ratio |
Value
Returns the required sample size for each group
Examples
size.ci.prop2(.05, .4, .2, .15, 1)
# Should return:
# n1 n2
# 274 274
size.ci.prop2(.05, .4, .2, .15, .5)
# Should return:
# n1 n2
# 383 192
[Package statpsych version 1.8.0 Index]