Confidence interval for a 2-group reliability difference

Computes a 100(1 - alpha)% confidence interval for a difference in population reliabilities in a 2-group design. This function can be used with any type of reliability coefficient (e.g., Cronbach alpha, McDonald omega, intraclass reliability). The function requires a point estimate and a 100(1 - alpha)% confidence interval for each reliability as input.

Usage

ci.rel2(rel1, ll1, ul1, rel2, ll2, ul2)

Arguments

rel1

estimated reliability for group 1

ll1

lower limit for group 1 reliability

ul1

upper limit for group 1 reliability

rel2

estimated reliability for group 2

ll2

lower limit for group 2 reliability

ul2

upper limit for group 2 reliability

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.rel2(.4, .35, .47, .2, .1, .32)
#>  Estimate   LL        UL
#>       0.2 0.07 0.3220656

# Should return:
# Estimate   LL        UL
#      0.2 0.07 0.3220656