size.ci.slope: Sample size for a slope confidence interval

In statpsych: Statistical Methods for Psychologists

Sample size for a slope confidence interval

Description

Computes the total sample size required to estimate a population slope with desired confidence interval precision in a between-subjects design with a quantitative factor. In an experimental design, the total sample size would be allocated to the levels of the quantitative factor and it might be necessary to increase the total sample size to achieve equal sample sizes. Set the error variance planning value to the largest value within a plausible range for a conservatively large sample size.

Usage

size.ci.slope(alpha, evar, x, w)

Arguments

alpha	alpha level for 1-alpha confidence
evar	planning value of within group (error) variance
x	vector of x values of the quantitative factor
w	desired confidence interval width

Value

Returns the required total sample size

Examples

x <- c(2, 5, 8)
size.ci.slope(.05, 31.1, x, 1)

# Should return:
# Total sample size
#                83
 

statpsych documentation built on Sept. 11, 2024, 7:42 p.m.