Sample size for a Cronbach reliability confidence interval

Computes the sample size required to estimate a Cronbach reliability with desired confidence interval precision. Set the reliability planning value to the smallest value within a plausible range for a conservatively large sample size.

Usage

size.ci.cronbach(alpha, rel, r, w)

Arguments

alpha

alpha value for 1-alpha confidence

rel

reliability planning value

r

number of measurements (items, raters, forms)

w

desired confidence interval width

Value

Returns the required sample size

Details

For more details, see Section 4.26 of Bonett (2021, Volume 1)

References

Bonett DG, Wright TA (2015). “Cronbach's alpha reliability: Interval estimation, hypothesis testing, and sample size planning.” Journal of Organizational Behavior, 36(1), 3–15. ISSN 08943796, doi:10.1002/job.1960 .

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

Examples

size.ci.cronbach(.05, .75, 5, .15)
#>  Sample size
#>          109

# Should return:
# Sample size
#         109