| size.test.mann {statpsych} | R Documentation |
Sample size for a Mann-Whitney test
Description
Computes the sample size in each group (assuming equal sample sizes) required for the Mann-Whitney test with desired power. A planning value of the Mann-Whitney parameter is required. In a 2-group experiment, this parameter is the proportion of members in the population with scores that would be larger under treatment 1 than treatment 2. In a 2-group nonexperiment where participants are sampled from two subpopulations of sizes N1 and N2, the parameter is the proportion of all N1 x N2 pairs in which a member from subpopulation 1 has a larger score than a member from subpopulation 2.
Usage
size.test.mann(alpha, pow, p)
Arguments
alpha |
alpha level for hypothesis test |
pow |
desired power |
p |
planning value of Mann-Whitney parameter |
Value
Returns the required sample size for each group
References
Noether GE (1987). “Sample size determination for some common nonparametric tests.” Journal of the American Statistical Association, 82(398), 645–647. ISSN 0162-1459, doi:10.1080/01621459.1987.10478478.
Examples
size.test.mann(.05, .90, .3)
# Should return:
# Sample size per group
# 44