Confidence interval for a difference in Cronbach reliabilities in a 2-group design

Source: R/statpsych2.R

Computes a confidence interval for a difference in population Cronbach reliability coefficients in a 2-group design. The number of measurements (e.g., items or raters) used in each group need not be equal.

ci.cronbach2(alpha, rel1, rel2, r1, r2, n1, n2)

Arguments

alpha

alpha level for 1-alpha confidence

rel1

estimated Cronbach reliability for group 1

rel2

estimated Cronbach reliability for group 2

r1

number of measurements used in group 1

r2

number of measurements used in group 2

n1

sample size for group 1

n2

sample size for group 2

Value

Returns a 1-row matrix. The columns are:

  • Estimate - estimated reliability difference

  • LL - lower limit of the confidence interval

  • UL - upper limit of the confidence interval

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 .

Examples

ci.cronbach2(.05, .88, .76, 8, 8, 200, 250)
#>  Estimate         LL       UL
#>      0.12 0.06973411 0.173236

# Should return:
# Estimate         LL       UL
#     0.12 0.06973411 0.173236