An important aspect of customer service and satisfaction at the Big Country theme park is the maintenance of the restrooms throughout the park. Customers expect the restrooms to be clean; odorless; well stocked with soap, paper towels, and toilet paper; and to have a comfortable temperature. In order to maintain quality, park quality control inspectors randomly inspect restrooms daily (during the day and evening) and record the number of defects (incidences of poor maintenance). The goal of park management is approximately 10 defects per inspection period. Following is a summary of the observations taken by these inspectors for 20 consecutive inspection periods:

Construct the appropriate control chart for this maintenance process using 3σ limits and indicate if the process was out of control at any time. If the process is in control, use pattern tests to determine if any nonrandom patternsexist.

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Number of Defects Number of Defects Sample 12 14 Sample 14 12 16 18 10