Reliability and motor memory.
The generalizability framework was employed to estimate variance components and reliability of performance in a positioning task. The subjects (n =70) performed 16 trials at each of three target lengths of 25 cm, 45 cm, and 65 cm. The data were analyzed using a subjects x targets x trials repeated measures ANOVA. Two reliability coefficients were estimated. The first (R) provided an estimate of performance reliability generalized over targets and trials. The second (R') treated targets as a source of true-score variance and hence was generalized over trials alone. Both reliability coefficients were higher for algebraic error than for absolute error, and R1 provided higher reliability estimates than R for both dependent variables. Increasing the number of positioning trials from 2 to 16 at each target length did not appreciably alter either reliability coefficient. The overall low reliability of R appears to compound the dependent variables and statistical power problems associated with short-term motor-memory studies.