How To Take An Activity Sample
We don't actually know the percentage occurance of our activities until we have performed the study, but if we work on the worst case scenario, where our percentage occurance of any one activity is 50%, for a sample requiring an accuracy of +/-5%:
n = 4 x 50(100 - 50)/5 x 5.
n = 10000/25
Number or observations required = 400.
Using the same formula for an accuracy of +/-10% this figure is 100.
The sample is then conducted with the required number of observations taken, spread over the representative time period. The activities are recorded for each operator/process/machine and analysed against each other using the percentages as the main criterion.