Computes a one-tailed (or two-tailed) CI at the desired level for coefficient alpha
Usage
alpha.CI(alpha, k, N, level = 0.90, onesided = FALSE)
Arguments
alpha
coefficient alpha to use for CI construction
k
number if items
N
sample size
level
Significance Level for constructing the CI, default is .90
onesided
return a one-sided (one-tailed) test, default is FALSE
Details
By inputting alpha, number of items and sample size, one can make inferences via
a confidence interval. This can be used to compare two alpha coefficients (e.g., from
two groups), or to compare alpha to some specified value (e.g., > = .7). onesided = FALSE renders
a two-sided test (i.e., this is the difference between tails of .025/.975 and .05/.95)
Value
Returns a table with 3 elements
LCL
lower confidence limit of CI
ALPHA
coefficient alpha
UCL
upper confidence limit of CI
Warning
You must first compute alpha and then enter into function. alpha.CI
will not evaluate a data.frame or matrix object.
Note
Feldt et al., provide a number of procedures for making inferences about alpha
(e.g., F test of the null hypothesis). Since the CI is the most versatile, it is the only function
created in this package