A new industrial oven has just been installed at Piatt Bakery. To develop experience regarding the oven temperature, an inspector reads the temperature at four different places inside the oven each half hour starting at 8:00 a.m. The last reading was at 10:30 a.m., for a total of six samples. 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.)

a. 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.

b. Interpret the chart. Does there seem to be a time when the temperature is out of control?