In preparation for their 2008 merger, Delta Airlines and Northwest Airlines undertook a comparative study of their on-time performance. The following table shows each airline's on-time record for a common two-month period for three cities where they both operated.
Delta Airlines Flights Northwest Airlines Flights
|
New York
|
Total
1987
|
Late
484
|
Total
399
|
Late
120
|
|
Chicago
|
718
|
118
|
1123
|
222
|
|
Memphis
|
193
|
24
|
536
|
70
|
|
Total
|
2898
|
626
|
2058
|
412
|
a. Northwest's operations executives claim to have superior overall on- time results. Does the data support this claim?
b. Delta's executives respond by pointing to its superior performance at key cities. Does the data support this claim?
c. Explain carefully how to reconcile your answers in parts (a) and (b). In your view, which is the better measure of performance-an aggregate measure or a disaggregate measure?