Question

1. Suppose an airline claims that its flights are consistently on time with an average delay of at most 15 minutes. It claims that the average delay is so consistent that the variance is no more than 15 minutes. Doubting the consistency part of the claim, a disgruntled traveler calculates the delays for his next 25 flights. The average delay for those 25 flights is 22 minutes with a standard deviation of 15 minutes.

Answer 1

H0: Null Hypothesis: 15 ( the average delay is so consistent that the variance is no more than 15 minutes. ) (Claim)

HA: Alternative Hypothesis: 15 ( the average delay is not consistent. the variance is more than 15 minutes. )

n = 25

s2 = 152 = 225

Take = 0.05

df = 25 - 1 = 24

From Table, critical value of = 36.415

Test Statistic is given by:

Since calculated value of = 360.00 is greater than critical value of = 36.415, the difference is significant. Reject null hypothesis.

Conclusion:

The data do not support the claim that the average delay is so consistent that the variance is no more than 15 minutes.