Coefficient alpha is a measure of internal consistency. It is a standard measure of
reliability for tests.
Usage
alpha(x)
Arguments
x
Data.frame or matrix object with rows corresponding individuals and columns to items
Value
coefficient alpha
Details
You can specify any portion of a matrix or data.frame. For instance, if using a data.frame
with numerous variables corresponding to items, one can specify subsets of those items. See examples
below.
alpha <- $k/(k-1)*(1-SumSxi/Sx)$
where k is the number of items, Sx is the standard deviaton of the total test, and SumSxi is the
sum of the standard deviations for each item.
References
Cronbach, L. J. (1951). Coefficient alpha and the internal structure of tests.
Psychometrika, 6, 297-334.