A metropolitan police agency is studying the incidence of drivers operating their vehicles without the minimum liability insurance required by law. The data are collected from drivers who have been stopped by an officer for a traffic law violation and a traffic summons issued. Data from three shifts over a ten-day period are shown in Table 7E.19.

(a) Set up a u-chart for these data. Plot the data from Table 7E.19 on the chart. Is the process in statistical control?
(b) Use n = 30 shifts and the shift averages to perform a 1-sample t-test of the hypotheses:

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TABLE 7E. 19 Data for Exercise 7.65 Number of Number of Drivers Without Insurance of Number of Drivers Without Insurance Sample Citations Sample Citations 7 10 10 12 13 14 15