A-79 Flynn Effect Correction: Accuracy Base Rate for IQ/Ability Level

Abstract

Abstract Objective Flynn Effect (FE) is the observed rise in population psychometric intelligence quotient (IQ) scores over time, approximately three IQ points per decade. Sometimes in forensic evaluations, points are deducted from archival IQ scores to “correct” for FE. This study determined the accuracy of FE correction for three IQ ranges. Method Participants were 240 people (age: M = 52.7, SD = 24.4; 149 female) from the WAIS-IV standardization group who took the WAIS-III and WAIS-IV in counterbalanced order with an inter-test interval from 6-163 days. WAIS-IV Full Scale IQ (FSIQ) scores were subtracted from WAIS-III scores and differences were divided into two groups: 1.) > 2 IQ points – when applying FE correction to a WAIS-III score produced a more accurate estimate and 2.) < 1 IQ points – when applying FE correction produced a less accurate estimate. Accuracy base rates were tabulated for three WAIS-III FSIQ groups: below average < 89; average 90-109; and above average groups > 110. Results FE correction produced more accurate WAIS-IV FSIQ estimates for 70% of the below average group, 56% of the average group, and 65% of the above average group. Conclusions Applying an FE correction provides a more accurate WAIS-IV IQ estimate about half the time for average IQ scores and about two-thirds of the time for above and below average IQ scores. (Standardization data from the WAIS-III Copyright © 1997 NCS Pearson Inc. & WAIS-IV Copyright © 2008 NCS Pearson Inc. Used with permission. All rights reserved.)