$($i$)$ Computerized work sampling will become an increasingly popular method in the future. What are the possible applications of such a method?

$($ii$)$ How can the validity of work sampling be sold to the operator not familiar with probability and statistical procedure?

$($iii$)$ It has been decided to determine the percentage of idle time for the numerically$-$controlled lathe machine. A trial study revealed that out of $150$ observations, $30$ observations showed that the machine was idle. Determine the number of random observations$($sample size$)$ required to achieve an accuracy of $+/-10\%$ at a confidence level of $95\%.$