size.ci.lc.stdmean.ws {statpsych} | R Documentation |
Computes the sample size required to estimate two types of standardized linear contrasts of population means (unweighted standardizer and single level standardizer) with desired confidence interval precision in a within-subjects design. For a conservatively large sample size, set the standardized linear contrast of means planning value to the largest value within a plausible range, and set the Pearson correlation planning value to the smallest value within a plausible range.
size.ci.lc.stdmean.ws(alpha, d, cor, w, q)
alpha |
alpha level for 1-alpha confidence |
d |
planning value of standardized linear contrast |
cor |
planning value of average correlation between measurements |
w |
desired confidence interval width |
q |
vector of within-subjects contrast coefficients |
Returns the required sample size for each standardizer
Bonett DG (2009). “Estimating standardized linear contrasts of means with desired precision.” Psychological Methods, 14(1), 1–5. ISSN 1939-1463, doi: 10.1037/a0014270.
q <- c(.5, .5, -.5, -.5) size.ci.lc.stdmean.ws(.05, 1, .7, .6, q) # Should return: # Sample size # Unweighted standardizer: 26 # Single level standardizer: 35