An SRS of 100 flights of a large airline (call this airline 1)
showed that 64 were on time. An SRS of 100 flights of another large
airline (call this airline 2) showed that 80 were on time. Let p1
and p2 be the proportion of all flights that are on time for these
two airlines. Reference: Ref 8-10 A 90% confidence interval for the
difference p1 – p2 is: 0.16 ± 0.080. –0.16 ± 0.103. –0.16 ± 0.062.
0.16 ± 0.062.