9. Data froen an 8-h work sampling study are shown below. a. What percentage of the time is the machine runaing? b. What percentage of the time is the machine brokea? c. What is the limit of accuracy of this stedy for a =0.05 ? d. What is the 95 percent confidence interval of the machine running? e. Your manager says that the range in part d is unacceptably large, She would like to narros the range doun to \pm 1 min of running time. How many observations should you collect to achieve this? CHAPTER 14 10. Dorben Co. provides a 10 percent allowance for its operators, A work sampling study of one operator over an 8-h shift yields the following data. Average rated perfocmance is 110 percent. Expected outpet is $0 unitsshift. a. What is the observed lime (in miestes) for loading? b. What is the normal time for unlcading? c. What is the averall standard time? d. What is the accuracy of the stady? 11. A work sampling analyst notices that our of 50 observations, a worker is taking a break 2 times, is charting to a coworker 2 times, and is absent from the workstation once. The analyst is 95 percent coefident that the worker is actually working from percent to percent of the time. If the statement is changed to say that the analyst is 95 pereent confidees that the worker is working from 87 percent to 93 percent of the time, what champes have occurred in the work stmpling study? 12. The following obeervations were obbained randomly over an 8-hour time perind on the Zip operator, during wtich time he assembled 20 Zip drives. a. How many minutes of a typical 8-h work day is the zip operator working? b. What is the average performance of the Zip cperator? c. What is the nocmal time for the Zip operator? d. What is the oferor for this study