ABSTRACT

Sampling is a term typically used in industry to distinguish random or periodic observations from continuous observations. As an alternative to continuous observation, sampling has both advantages and disadvantages. On the advantage side, sampling is usually much less costly to perform. But it does have the disadvantage that results can be incorrect when sampling is improper. The key point in sampling is summed under the question, “can one obtain an accurate condition of the situation during a brief or at least short-term observation?” Unless an affirmative answer can be given, sampling should not be considered. It was that key observation that Tippett, the originator of activity analysis, made when he listened to the knitting mills in the midlands of England in the early 1930s. He noted that a momentary listening to the mills would disclose whether the machines were working properly. He called the sampling technique “ratio delay,” and one occasionally hears that term yet today.