On time. Airlines strive to have f lights arrive on time.

Transportation statistics (www.transtats.bts.gov) report the percentage of scheduled f lights arriving on time in each month. We have data for 2005–2010. Flights can fail to be on time for a variety of reasons, but do the on-time rates vary by month? We performed an ANOVA. The partially completed analysis of variance table is shown here.

Source DF Sum of Squares Mean Square F-ratio P-value Month 11 1047.92 Error 59 839.450 Total 70 1887.37

a) Is this an experimental or observational study? Explain.

b) Is this a prospective or retrospective study? Explain.

c) State the null and alternative hypotheses.

d) Calculate the F-statistic.

e) The P-value for this statistic turns out to be 60.0001.

State the conclusion. Can a causal link be established?

Explain.