The Wechsler Adult Intelligence Scale-IV Cognitive Proficiency Index: alternate form reliability of the nine possible subtest tetrads.

The Wechsler Adult Intelligence Scale (WAIS-IV) added a new interpretative level by assigning the ten standard subtests into one of two constructs, the General Ability Index or the Cognitive Proficiency Index (CPI). The CPI, inferred to be a non-intellective measure of information processing efficiency, is composed of the two Working Memory Index and the two Processing Speed Index subtests (DS, AR, CD, SS). However, each index has one supplemental subtest that can be used in place of a standard one, thereby creating nine possible CPI tetrads, except for senior adults 70-90.