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Control charts of mean

A new industrial oven has just been installed at the Piatt Bakery. To develop experience regarding the oven temperature, an inspector reads the temperature at four different places inside the oven each half hour. The first reading, taken at 8:00 A.M., was 340 degrees Fahrenheit. (Only the last two digits are given in the following table to make the computations easier.)

Reading
Time 1 2 3 4
8:00 A.M. 40 50 55 39
8:30 A.M. 44 42 38 38
9:00 A.M. 41 45 47 43
9:30 A.M. 39 39 41 41
10:00 A.M. 37 42 46 41
10:30 A.M. 39 40 39 40

1. On the basis of this initial experience, determine the control limits for the mean temperature. Determine the grand mean. Plot the experience on a chart.
2. Interpret the chart. Does there seem to be a time when the temperature is out of control?
Refer to exercise 7.
3. On the basis of this initial experience, determine the control limits for the range. Plot the experience on a chart.
4. Does there seem to be a time when there is too much variation in the temperature?

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