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Review practice:Chapter 15§A work sampling study was performed during a three-hour finalexam to determine the proportion of time that students spend usinga calculator. There were 70 students taking the exam. A total of fiveobservations were taken of each student at random times duringthe three hours. Of the total observations taken, 77 of theobservations found the students using their calculators.§(a) Form a 90% confidence interval on the proportion of timestudents spend using their calculators during an exam.§(b) How many observations must be taken for the analyst to be95% confident that the estimate of proportion of time a studentuses a calculator is within ±.03 of the true proportion?2
§The Chief IE in the production department wanted to know what value of PFD allowance to use for aparticular section of the shop. A work sampling study was authorized. Only three activity categories wereconsidered: (1) production work, (2) personal time, rest breaks, and delays, and (3) other activities. Over afour-week period (40 hours/week), 100 observations were made at random times. Each observationcaptured the category of activity of each of 22 production workers in the department. Results indicated thatcategory 2 constituted 19% of the total observations.§(a) Define the limits of a 95% confidence interval for activity 2.§(b) If a total of 522 work units were produced during the 4 weeks, and the 1540 observations in category 1activity were all devoted to producing these units, what was the average time spent on each unit?2
(b) GivenQ= 522 work units
Chapter 13:Seven cycles have been observed during adirect time study. The mean for the largestelement time = 0.85 min, and the correspondingsample standard deviations= 0.15 min, whichwas also the largest. If the analyst wants to be95% confident that the mean of the sample waswithin±10% of the true mean, how many moreobservations should be taken?=

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