Difference score reliabilities within the RIAS‐2 and WISC‐V

Abstract

Many prominent intelligence tests (e.g., WISC-V & RIAS-2) offer methods for computing subtest-and composite-level difference scores. This current study uses data provided in the technical manual of the Wechsler Intelligence Scale for Children, Fifth Edition (WISC-V) and Reynolds Intellectual Abilities Scale, Second Edition (RIAS-2) to calculate reliability coefficients for difference scores. Subtest-level difference score reliabilities range from 0.59 to 0.99 for the RIAS-2 and from 0.53 to 0.87 for the WISC-V. Composite-level difference score reliabilities range from 0.23 to 0.95 for the RIAS-2 and from 0.36 to 0.87 for the WISC-V, with the exception of the FSIQ > GAI comparison, which resulted in a reliability of 0.00. Emphasis is placed on comparisons recommended by test publishers and a discussion of minimum requirements for interpretation of differences scores is provided.