Bennett, Alpert &amp; Goldstein’s "S" is a statistical measure of inter-rater agreement. It was created by Bennett "et al." in 1954.
Rationale for use.
Bennett "et al." suggested adjusting inter-rater reliability to accommodate the percentage of rater agreement that might be expected by chance was a better measure than simple agreement between raters. They proposed an index which adjusted the proportion of rater agreement based on the number of categories employed.
Mathematical formulation.
The formula for "S" is
 formula_1
where "Q" is the number of categories and "P"a is the proportion of agreement between raters.
The variance of "S" is
 formula_2
Notes.
This statistic is also known as Guilford’s "G". Guilford was the first person to use the approach extensively in the determination of inter-rater reliability.
References.
 ;templatestyles src="Reflist/styles.css" / ;