A study of work-time distributions on unpaced tasks

This research had two objectives. First, to examine the possible superiority of any of the three principal MTM systems for the derivation of time standards, recognizing the natural variability of actual work times arising from unpaced operator performance. Then, to consider whether the use of further simplifications of predetermined motion time systems, which may be derived from MTM, might permit equally acceptable time standards to be obtained. Factory studies were used to compare the standards predicted by MTM-1, 2 and 3 against actual performance by well trained. workers. No significant difference was detected between the times predicted by MTM-1, MTM-2 and MTM-3. Four simplified systems were developed from the factory data and, except for the system in which motion cases were ignored, no statistically significant\differences were found between cycle times predicted by these systems and by the general levels of MTM. Times for similar operations in the same factory as the original sample were determined using MTM-1, MTM-2, MTM-3 and two simplified systems. The results were equally acceptable by each of these five systems. Further testing based upon maintenance type work data did not show a satisfactory transferability of simplified systems into this entirely different working environment. The study did not support the widely held view that there are minimum cycle times below which MTM-2 and MTM-3 should not be used to establish a time standard. In considering the variability of the actual work times, it was not possible to account for the individual effects of factors which create variability of operators performing unpaced tasks. Nevertheless, a representative distribution for this variability was estimated, in which the variability of the operator work-time was related to the average cycle time.