Percent idle time for men and machine is found by

Explanation:

Work Sampling

• Work sampling is a measurement technique for the quantitative analysis, in terms of time, of the activities of men, machines, or any observable state or condition of operation.
• It is especially useful in the analysis of nonrepetitive or irregularly occurring activity, where no complete methods and frequency descriptions are available.
• A work sampling study consists of a large number of observations taken at random intervals. In taking the observations, the condition of the object of study is recorded, and this condition is categorized into predefined groups of activities peculiar to the particular work situation.
• From the proportions of observations falling into each of the categories, interferences are drawn concerning the total work activity under study.
• As an example, if a group of production operators are observed to be waiting for material in a third of the observations of their work activity, we might draw the inference that better material planning and scheduling, rather than better work methods, represent the most obvious area for improvement.
• The underlying theory of work sampling, then, is that the percentage of observations recording either a man or machine as idle, or as working, or in any other condition reflects a known degree of accuracy the average percentage of time actually spent in that state or condition.
• If the observations are randomly distributed over a sufficiently long period of time, this theory is held to be true, regardless of the nature of the observed activity.