In the flight delays case study in Section 1.1, the data contains flight delays for two airlines, American and United.

a) Compute the proportion of times that each carrier's flights was

delayed more than 20 min. Conduct a two-sided test to see if the difference in these proportions is statistically significant (see the R Note in Example 3.6).

b) Computethevarianceintheflightdelaylengthsforeachcarrier.Con- duct a test to see if the variance for United Airlines differs from that of American Airlines.