A cook at Bill’s restaurant (see problem 3) has devised a new method of quickly flipping and pressing hamburgers that he believes will save time in cooking the second side of hamburgers (work element 3 in Table H.2). The cook asked a peer to conduct a time study for this work element, with the results shown in Table H.3. This cook is renowned for superior strength and speed in hamburger flipping and pressing. The rating factor for this study is 1.2. Allowances typically constitute 15 percent of the normal time.
a. What is the average of select times for revised work element 3? For the revised normal time?
b. What is the revised normal time per cycle? The revised standard time?
c. The managers seem very interested in this revised method for work element 3. They say that if they could be sure the average of the select times for this study was within ±13 percent of the true average time for this new method, they could afford to buy health insurance for the part-time cooks. How many observations would be required to be 98 percent confident that the average of select times for this study was within ±13 percent of the true mean?

d. The cook is not only quick with a spatula, but also quick with a calculator and a bit suspicious of management’s motives. If the average of the select times found in part (c) were inflated by 13 percent, how many cooks would Bill’s restaurant need?

Data From Problem 3

A time study involving the preparation of hamburgers at Bill’s fast-food restaurant used the snap-back method to obtain the data (in minutes) shown in Table H.2. Allowances typically constitute 15 percent of normal time. The schedule calls for 300 hamburgers to be prepared during the lunch rush. If each part-time employee works 190 minutes per day, how many employees will be needed?

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TABLE H.2 TIME STUDY RESULTS OF HAMBURGER PREPARATION OBSERVATION Work Element 3 4 RF NT 1. Prepare patty 2. Cook first side 0.41 1 0.45 0.50 0.48 0.36 0.9 0.85 0.81 0.77 0.89 0.83 1.2 3. Flip, press, and cook other side 0.55 0.59 0.58 1.2 1 0.60 0.63 0.31 0.32 0.26 4. Assemble 0.24 0.27 1.0 Normal time per cycle (NTC) LO TABLE H.3 WORK ELEMENT 3 TIME STUDY OBSERVATION Work Element Revised Work Element 3 3 4 10 0.31 0.39 0.29 0.33 0.45 0.50 0.48 0.31 0.44 0.40