prec_icc: Sample size or precision for an intraclass correlation

In a-lenz/presize: Precision Based Sample Size Calculation

Description

prec_icc returns the sample size or the precision for the given intraclass correlation

Usage

prec_icc(rho, k, n = NULL, conf.width = NULL, conf.level = 0.95)

Arguments

rho	Desired intraclass correlation.
k	number of observations per n (subject).
conf.width	precision (the full width of the conficende interval)
conf.level	confidence level

Details

Exactly one of the parameters n, conf.width must be passed as NULL, and that parameter is determined from the other.

Sample size or precision is calculated according to formula 3 in Bonett (2002), which is an approximation. Whether ICC is calculated for a one-way or a two-way ANOVA does not matter in the approximation. As suggested by the author, 5*rho is added to n, if k = 2 and rho ≥ 7.

n is rounded up to the next whole number using ceiling.

References

Bonett DG (2002). Sample size requirements for estimating intraclass correlations with desired precision. Statistics in Medicine, 21:1331-1335. doi:10.1002/sim.1108

a-lenz/presize documentation built on May 17, 2019, 7:44 a.m.