nDep2sam: Simple random sample size for difference in means

In PracTools: Tools for Designing and Weighting Survey Samples

Simple random sample size for difference in means

Description

Compute a simple random sample size for estimating the difference in means when samples overlap

Usage

nDep2sam(S2x, S2y, g, r, rho, alt, del, sig.level=0.05, pow=0.80)

Arguments

S2x	unit variance of analysis variable x in sample 1
S2y	unit variance of analysis variable y in sample 2
g	proportion of sample 1 that is in the overlap with sample 2
r	ratio of the size of sample 1 to that of sample 2
rho	unit-level correlation between x and y
alt	should the test be 1-sided or 2-sided; allowable values are alt="one.sided" or alt="two.sided".
del	size of the difference between the means to be detected
sig.level	significance level of the hypothesis test
pow	desired power of the test

Details

nDep2sam computes sample sizes in two groups that are required for testing whether the difference in group means is significant. The power of the test is one of the input parameters. The samples have a specified proportion of units in common. Both samples are assumed to be selected via simple random sampling.

Value

List with values:

n1	sample size in group 1
n2	sample size in group 2
S2x.S2y	unit variances in groups 1 and 2
delta	difference in group means to be detected
gamma	proportion of sample 1 that is in the overlap with sample 2
r	ratio of the size of sample 1 to that of sample 2
rho	unit-level correlation between analysis variables in groups 1 and 2
alt	type of test: one-sided or two-sided
sig.level	significance level of test
power	power of the test

Author(s)

Richard Valliant, Jill A. Dever, Frauke Kreuter

References

Valliant, R., Dever, J., Kreuter, F. (2018, chap. 4). Practical Tools for Designing and Weighting Survey Samples, 2nd edition. New York: Springer.

Woodward, M. (1992). Formulas for Sample Size, Power, and Minimum Detectable Relative Risk in Medical Studies. The Statistician, 41, 185-196.

See Also

nProp2sam

Examples

nDep2sam(S2x=200, S2y=200,
            g=0.75, r=1, rho=0.9,
            alt="one.sided", del=5,
            sig.level=0.05, pow=0.80)

PracTools documentation built on Nov. 9, 2023, 9:06 a.m.