SPED Assessment In 2002 the American Association on Mental Retardation (AAMR) made changes to their manuals regarding the assessment of mental retardation (MR). The revisions were designed to affect changes in professional practice regarding assessment of MR, public policy, and the science and understanding of MR. Key in this change was the attempted change from the MR term to a more politically correct term Intellectual Disability. Assessment was to consider both IQ scores and adaptive behavior (AB) which was to be termed "adaptive skills as well as the individual's cultural background and in the context of associated strengths. Instead of following a deficit model of explanation the goal was to follow a needs model. The definition of intellectual disability then includes three core criteria: significant impairment of intellectual functioning (defined by decreased IQ scores), significant impairment of adaptive/social functioning and, onset before adulthood. Polloway et al. (2009) looked at the impact of these changes on state guidelines for the assessment and treatment of MR. Interestingly, 27 states still formally used the MR term in their guidelines/definitions with only four using the recommended term. Most states still adopted older formal definitions on MR. With respect to IQ scores, the topic of this paper, only 12 states reported no specific IQ cutoff score was needed for the diagnosis, whereas those reporting a specific IQ score typically used the 70 or 70-75 cutoff score either by formal definition or maintaining a score of two standard deviations below the mean was the cutoff score. Forty-nine states required deficits in AB. Age guidelines and an classification system (e.g., designating mild MR, moderate MR, etc.) were variably employed. Polloway et al. (2009) pretty much leave the IQ assessment issue alone, suggesting that it is a cornerstone...

And here is where this study, although primarily descriptive in nature, totally misses the point. In fact IQ scores as a method of assessing MR have severe limitations and certainly warrant more attention regarding the accurate assessment of MR than whether a state terms the condition MR, cognitive impairment, or intellectual disability.
One issue with IQ scores is their consistency over time, especially at the lower end of the continuum in IQ distributions. Changes in IQ scores across time are often explained as artifacts of random or systemic error. This is why it may often be best to report confidence intervals as opposed just too reporting point estimates of IQ. However, Whitaker (2008) performed a meta-analysis of those obtaining low IQ scores (less than a Full Scale IQ of 80) that were retested at a mean interval time of 2.8 years. Despite the reporting in most IQ manuals of 95% confidence intervals of about five IQ points either side of the obtained score, Whitaker found that 14% of the scores in the meta-analysis changed by 12.5 points or more. Moreover, stability at the lower ends of the subtest score distribution is questionable and floor effects exist. For instance, in the Wechsler IQ protocols a raw score of zero on a subtest often still yields a scaled score of one or higher in older individuals who are given the WAIS and not the WISC tests. This means that scaled scores will often overestimate the person's ability on that particular domain. When these overestimates occur there are some serious ramifications in the classification of MR individuals who need special education. If IQ scores cannot show constancy over time, then their utility is questionable as the mainstream form of assessment for classifying special needs students with MR or in cases where the death penalty is involved and a cognitive assessment is crucial to the life of a person (it is against the law to execute person with MR who is convicted of a crime).

There are no standardized or formalized recommendations of which IQ test should provide the best estimate intellectual disability as different tests will yield different results, even when given to the same person. This effect has been observed even in tests produced by the same manufacturer. For instance, Gordon, Duff, Davison, and Whitaker (2010) observed that in the past the…