Statistical significance and reliability of single-subtest and cluster deviation scores

Suppose one has a battery of K subtests and a composite for the battery is defined as the mean of the K standardized subtest scores. An individual's single-subtest deviation score is the difference between the individual's score on any single subtest and his composite score. A cluster deviation score is the difference between an examinee's average for a small set (cluster) of subtests and his composite. Formulas are given for the test of statistical significance of the individual's subtest or cluster deviation score and the internal consistency reliability of such deviation scores.