size.ci.condmean: Sample size for a conditional mean confidence interval

In statpsych: Statistical Methods for Psychologists

Sample size for a conditional mean confidence interval

Description

Computes the total sample size required to estimate a population conditional mean of y at x = x* in a fixed-x simple linear regression model with desired confidence interval precision. 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.condmean(alpha, evar, xvar, diff, w)

Arguments

alpha	alpha level for 1-alpha confidence
evar	planning value of within group (error) variance
xvar	variance of fixed predictor variable
diff	difference between x* and mean of x
w	desired confidence interval width

Value

Returns the required total sample size

Examples

size.ci.condmean(.05, 120, 125, 15, 5)

# Should return:
# Total sample size
#               210
 

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