A Car Mechanic Is Thinking of Guaranteeing Customers That an Oil

question 91

Essay

A car mechanic is thinking of guaranteeing customers that an oil change will take no more than 15 minutes with a 99.73% confidence level. He takes a few samples of size 5 and finds the process mean to be 13 minutes with a standard deviation of .2 minutes and average sample range of 1.2 minutes. Find the A₂, D₂, and D₃ values and use them to compute the upper and lower limits for an x-bar chart. Use the upper limit to determine if the mechanic can offer a 15 minute guarantee. Assume the mechanic plots the samples on the x-bar control chart and finds the process is in control, is there anything else the mechanic is missing to ensure the process is in control?

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Definitions:

CDs

Short for Certificates of Deposit, which are savings certificates with a fixed maturity date and specified fixed interest rate that are issued by banks.

Budget Constraint

A budget constraint represents the limitations on the spending choices of consumers based on their income and the prices of goods and services.

DVDs

Digital Versatile Discs, a type of optical storage media used for storing data, including movies, software, and other digital information.

CDs

Compact Discs, a form of digital optical disc data storage, used for storing digital data, including music, software, and data files.