ci.cronbach2 {statpsych}

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

Description

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

Usage

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

Arguments

alpha

alpha level for 1-alpha confidence

rel1

estimated Cronbach reliablity for group 1

rel2

estimated Cronbach reliablity 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)

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