sampleSizeWilcoxTwoSample: Compute sample size for two sample Wilcoxon (Mann-Whitney)...

Description Usage Arguments Details Value Author(s) References Examples

Description

Compute sample size to test the hypothesis that two samples come from the same population against that Y's tend to be larger than X's.

Usage

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sampleSizeWilcoxTwoSample(a = 0.05, b = 0.2, c = 0.5, 
    pxy = 0.75, two.sided = TRUE)

Arguments

a

Significance level of test.

b

Desired power of test.

c

Proportion of observations in group 1: c = m / (m + n) (c = 0.5 means equally sized groups).

pxy

A value for the probability P(Y > X).

two.sided

If TRUE a two-sided test is assumed, otherwise one-sided.

Details

Given two independent samples X_1, ..., X_m and Y_1, ..., Y_n, we want to test the hypothesis that the two samples come from the same population against that Y's tend to be larger than X's.

Value

m

Sample size of the first group.

n

Sample size of the second group.

Author(s)

Kaspar Rufibach
kaspar.rufibach@gmail.com

References

Nother, G.E. (1987). Sample Size Determination for Some Common Nonparametric Tests JASA, 82, 644–647.

Examples

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# compute sample size for some pxy's
pxys <- c(0.65, 0.7, 0.75)
dat1 <- matrix(ncol = 3, nrow = length(pxys))
colnames(dat1) <- c("P(Y > X)", "m", "n")
for (j in 1:length(pxys)){dat1[j, ] <- c(pxys[j], 
    sampleSizeWilcoxTwoSample(a = 0.05, b = 0.1, c = 0.5, 
    pxy = pxys[j], two.sided = TRUE))}
dat1


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