Abstract
The stability of estimates of test-retest reliability was studied in a situation in which the interval separating observation periods was permitted to vary. Weekly production data were collected from 24 women sewing-machine operators, and 16 women in folding and packaging jobs. Correlations between performance periods were assembled into arrays each containing weeks separated by a fixed interval, K. The variability of the distribution of coefficients, Sr, was determined for each value of K, and the regression of S r on K was found to fit the general form Sr = K/(a + bK) for each group. Most of the increase in Sr occurred between the interval K = 1 to 25, and subsequent analyses yielded no significant relationship between the presence of aberrant reliability estimates and the time separating observation periods. Both magnitude of the reliability estimate and the accuracy with which the estimate is made vary as a function of the temporal dimension of the test-retest design.
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