Confidence interval for a subgroup difference in average Cronbach reliabilities

Source: R/meta_comp.R

Computes the estimate, standard error, and confidence interval for a difference in average Cronbach reliability coefficients for two mutually exclusive subgroups of studies. Each set can have one or more studies. The number of measurements used to compute the sample reliablity coefficient is assumed to be the same for all studies.

meta.sub.cronbach(alpha, n, rel, r, group)

Arguments

alpha

alpha level for 1-alpha confidence

n

vector of sample sizes

rel

vector of estimated Cronbach reliabilities

r

number of measurements (e.g., items)

group

vector of group indicators:

  • 1 for set A

  • 2 for set B

  • 0 to ignore

Value

Returns a matrix with three rows:

  • Row 1 - estimate for Set A

  • Row 2 - estimate for Set B

  • Row 3 - estimate for difference, Set A - Set B

The columns are:

  • Estimate - estimated average correlation or difference

  • SE - standard error

  • LL - lower limit of the confidence interval

  • UL - upper limit of the confidence interval

References

Bonett DG (2010). “Varying coefficient meta-analytic methods for alpha reliability.” Psychological Methods, 15(4), 368--385. ISSN 1939-1463, doi:10.1037/a0020142 .

Examples

n <- c(120, 170, 150, 135)
rel <- c(.89, .87, .73, .71)
group <- c(1, 1, 2, 2)
r <- 10
meta.sub.cronbach(.05, n, rel, r, group)
#>                Estimate         SE        LL        UL
#> Set A:             0.88 0.01068845 0.8581268 0.8999386
#> Set B:             0.72 0.02515130 0.6684484 0.7668524
#> Set A - Set B:     0.16 0.02732821 0.1082933 0.2152731

# Should return: 
#                Estimate         SE        LL        UL
# Set A:             0.88 0.01068845 0.8581268 0.8999386
# Set B:             0.72 0.02515130 0.6684484 0.7668524
# Set A - Set B:     0.16 0.02732821 0.1082933 0.2152731