Especially in the present case, in which the manual
effort of a low cost man-machine-system is intended to be
quantified for further automation decisions, the reality level,
largely determining the economic viability of the automation,
must be the dominant factor defining the success of the study
at hand. The times recorded during the time study in the
Cellular Manufacturing line serve as reality reference. The
average of the relative deviation value of each method for
each machine is used as quantifier. The desired 0% deviation
is set as a lower limit for the criterion. Regarding the upper
limit, each increase in deviation also increases the probability
for a wrong decision for or against automation. This calls for
a preferably low limit. However, previous experience for
MTM-1 for example shows a system-immanent deviation of
standard times of up to 10%. [18] In order to keep the
criterion at an operational level, 15% deviation is set as an
upper limit, above which the results are too inaccurate to
support a later automation decision.