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Graduate Statistics problems - MBA program

1. At quickie Car wash, the process is advertised to take less than 7 minutes. Consequently, management has set a target average of 390 seconds for the wash process. Suppose the average range for a sample of nine cars is 10 seconds.
Use the below Table 6.1 to establish control limits for sample means and ranges for the car wash process.

2. At Isogen Pharmaceuticals, the filling process for its asthma inhaler is set to dispense 150 milliliters ( ml) of Steroid solution per container. The average range for a sample of 4 containers is 3 ml.
Use the below Table 6.1 to establish Control Limits for sample Means and ranges for the filling process.

Table 6.1

(see attached file)

3.Garcia's garage desires to create some colorful charts and graphs to illustrate how reliably its mechanics "get under the hood and fix the problem."
The historic average for the proportion of customers that return for the same repair within the 30 day warranty period is 0.10
Each month, Garcia tracks 100 customers to see whether they return for warranty repairs.

The results are plotted as a proportion to report progress toward the goal.
If the control limits are to be set at two standard deviations on either side of the goal, determine the control limits for this chart.

In March, 8 of the 100 customers in the sample group returned for warranty repairs. Is the repair process in control?

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Solution Summary

This solution is comprised of a detailed explanation to use the below Table 6.1 to establish control limits for sample means and ranges for the car wash process.

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