A major airline surveys passengers to monitor the satisfaction level of its customers. Even though the airline uses a five-point Likert scale (5: outstanding service; 4: good; 3: average; 2: below average; 1: poor), it wants to monitor the proportion that considers the service level as either outstanding or good. Table 8-38 shows the number of passengers responding to the survey and the number that considers the service as either outstanding or good. Construct an appropriate control chart and comment on the service level of the airline.

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TABLE S-38 Passenger Satisfaction Survey in Airline Number Checking "Outstanding" or "Good" Number Checking "Outstanding" or "Good" Number Number Week Responded Week Responded 1 80 65 14 135 105 110 80 15 125 90 3 250 210 16 150 118 4 150 130 17 100 82 5 90 70 18 110 75 100 85 19 85 64 140 165 7 140 108 20 114 220 202 21 122 9 200 184 22 185 148 10 180 140 23 130 105 11 70 55 24 125 114 12 95 70 25 120 105 13 115 82