Sitwell Services cleans offices. It runs several cleaning crews that are given standard times for cleaning certain spaces. Given the experience of the crew, these standards can allow for more or less time. Crew B has just begun work for the company. It is evaluated using a rolling average standard that reflects the amount of improvement in its productivity. The following are the elapsed times for cleaning Joe’s Plumbing Supplies for six weeks.

REQUIRED:

Using three weeks as the basis for your lean accounting elapsed time metric, calculate the average time Crew B takes to complete the Joe’s Plumbing Supplies job over time. Specifically, use the first three weeks as your baseline, then add one new observation and delete one to get the Week 4 average, and so forth through Week 6.

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Week 1 120 minutes Week 2 115 minutes Week 3 110 minutes Week 4 105 minutes Week 5 100 minutes Week 6 95minutes