pi.var.upper: Upper prediction limit for an estimated variance

In statpsych: Statistical Methods for Psychologists

Upper prediction limit for an estimated variance

Description

Computes an approximate upper prediction limit for the estimated variance in a future study for a planned sample size. The prediction limit uses a variance estimate from a prior study. The upper variance prediction limit is useful as a variance planning value for the sample size required to obtain a confidence interval with desired width. This strategy for specifying a variance planning value is useful in applications where the population variance in the prior study is assumed to be similar to the population variance in the planned study. This variance planning value can be used to revise the planned sample size in the future study.

Usage

pi.var.upper(alpha, var, n1, n2)

Arguments

alpha	alpha value for upper 1-alpha confidence
var	estimated variance from prior study
n1	sample size used to estimate variance
n2	planned sample size of future study

Value

Returns an upper prediction estimate (UL) of an estimated variance in a future study

Examples

pi.var.upper(.2, 15, 40, 100)

# Should return:
#           UL
# [1] 18.78522
 

statpsych documentation built on July 9, 2023, 6:50 p.m.