Testing normal older people three or four times at 1- to 2-year intervals:Defining normal variance

Normative data were presented that defined the upper and lower standards fo r deciding if cognitive abilities show reliable change over 2 or more testi ng occasions when retesting occurs at 1- to 2-year intervals. The Mayo Cogn itive Factor Scores (MCFS; G. E. Smith et al., 1994) were analyzed because they permit the quantitation of overall functioning in 5 clinically importa nt cognitive domains: established verbal knowledge, nonverbal reasoning, at tention and concentration, new learning, and delayed memory. To the authors ' knowledge, this is the first report of both group-level and individual-le vel data analyses derived from a respectably sized sample of normal persons who have been tested 3 or more times at clinically common test-retest inte rvals.