Six Sigma and Process Improvement - Week 3 Assignment

Problem Solving

For this week, work and solve the problems 1, 2, and 4 below from chapter 4. You MUST show the work and interpret the results. The work MUST be submitted in Microsoft Word or Excel.

Problem 1

You are asked by the owner of the Moonbow Motel to develop a customer satisfaction survey to determine the percentage of customers who are dissatisfied with service. In the past year, 10,000 customers were serviced. The owner desires a 95 percent level of confidence with an allowable statistical error of ±0.01. From past estimates, she believes that about 3.5 percent of customers have expressed dissatisfaction. What sample size should you use for this survey?

Problem 2

A manager atLocaltel, a small telephone company, wants to determine how long service technicians need to perform a certain repair. In the past, an almost identical repair required 18.75 minutes, with a standard deviation of 0.2 minutes. Compute the sample size of times needing to be collected to ensure that they can be 90 percent confident of correctly estimating the repair time if the manager is willing to tolerate an error rate of 0.04.

Problem 4

The quality manager at theNoscrapShirt Company took a random sample of 10 workers’ output of good and defective shirts produced for 10 days each on a check sheet, as shown in the worksheet Prob04-04 in the Excel workbookCh04Data.xlsx. Find the proportion of defective shirts in the sample by using the Excel COUNTIF function. Recommend what management should do, based on these findings.

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