Methodological issues in short-term motor memory research.

Four methodological issues identified and studied by short-term motor memory researchers were examined in this paper: (a) the distributions of three commonly used measures of error (AE, CE, and VE); (b) statistical analysis of these scores as dependent measures in an experiment; (c) within-cell and experiment-wise estimates of the reliability of CE; and (d) the power of the statistical test with CE as the dependent measure. The first two sub-problems were explored theoretically, while the latter two were subjected to empirical examination using four data sets from previously published experiments. The distributions of AE and VE scores were described as non-normal under certain conditions, while the CE score distribution was shown to be normal. Therefore analyses of these three dependent measures may require different statistical procedures. In light of this information, the assumptions affecting estimates of reliability and power in an experimental framework were examined. Based on an analysis of the four data sets, a strategy was proposed in which a relatively small number of subjects could be utilized in an experiment without sacrificing desired experimental controls.