Sample size for a between-subjects mean linear contrast confidence interval

Computes the sample size in each group (assuming equal sample sizes) required to estimate a linear contrast of population means with desired confidence interval precision in a between-subjects design. Set the variance planning value to the largest value within a plausible range for a conservatively large sample size.

For more details, see Section 3.24 of Bonett (2021, Volume 1)

Usage

size.ci.lc.mean.bs(alpha, var, w, v)

Arguments

alpha

alpha level for 1-alpha confidence

var

planning value of average within-group variance

w

desired confidence interval width

v

vector of between-subjects contrast coefficients

Value

Returns the required sample size for each group

References

Bonett DG (2021). Statistical Methods for Psychologists https://dgbonett.sites.ucsc.edu/.

Examples

v <- c(.5, .5, -.5, -.5)
size.ci.lc.mean.bs(.05, 8.0, 3.0, v)
#>  Sample size per group
#>                     15

# Should return:
# Sample size per group
#                    15