The waiting time for treatment in a minute-clinic located in a drugstore is monitored using control charts

The waiting time for treatment in a €œminute-clinic€ located in a drugstore is monitored using control charts for individuals and the moving range. Table 6E.24 contains 30 successive measurements on waiting time.

(a) Set up individual and moving range control charts using this data.
(b) Plot these observations on the charts constructed in part (a). Interpret the results. Does the process seem to be in statistical control?
(c) Plot the waiting time data on a normal probability plot. Is it reasonable to assume normality for these data? Wouldn€™t a variable like waiting time often tend to have a distribution with a long tail (skewed) to the right? Why?

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TABLE 6E.24 Clinie Waiting Time for Exercise 6.66 Waiting Waiting Waiting Ohservation Time Observatien Time Observation Time 249 3.39 11 134 2 .14 1.66 0.50 741 13 4.35 23 4.67 1.67 163 4.88 17 5.1927 0.67 1.54 5.06 3.40 1.39 1.11 18 .14 2 6.92 30 3699 24 25 26 0.76 15 132 7.05 137 18 6 28 10 5.12 20 2.16