The data file stratflights.csv (http://people.ucalgary.ca/~jbstall/DataFiles/stratflights.csv)contains data that resulting from a random sample of flights leaving each of the three-NYC area international airports: Newark (EWR), JFK, and LaGuardia (LGA). These appear in the origin column. These flights were picked at random from all flights, N = 337, 776 in total, that left the these airports in 2013. Also NEW R = 120835 NJF K = 111279 NLGA = 104662
(a) Consider the variable dep delay, which records the difference between the time a flight is scheduled to leave and the time the flight actually pulls away from the jet-way (the departure time of the flight). Create a series of boxplots that shows the distribution of the departure delay (in minutes) from each of the three NYC-area international airports. (Note: You may have some flights in these data that are missing data on the dep delay variable.)
(b) Test the hypothesis that the standard deviation in the departure delay is the same for a flight leaving Newark, JFK, and LaGuardia. State the statistical hypothesis, provide the output and the value of the test statistic, and the P -value. What can you conclude from these data? Is your statistical result consistent with the data visualization you conducted in part (a).?
(c) Test the hypothesis that, on average, the time a flight is delayed is the same for Newark, JFK, and LaGuardia. Use as a level of confidence α = 0.01. As you did in part (b), state your statistical hypothesis, provide the value of the test statistic and the P -value, and your conclusion in the context of these data.
(d) Suppose you are flying out of one of these three airports. Compute the 95% confidence interval for μdep delay , the mean number of minutes a flight leaving any of the three NYC-area international airports is late in departing.
(e) Turn your attention to the distance variable, which measures the number of aeronautical miles be- tween the origin of the flight to the destination of the flight dest. Compute a 95% confidence interval for Tdistance, the total number of aeronautical miles for all flights leaving the three NYC-area in- ternational airports in 2013. For this interval, express your lower and upper bounds in millions of miles.
(f) The air time variable measures the length of each flight, in minutes. For example, the first record was a flight from JFK to Las Vegas, a flight that was 314 minutes in length. What proportion of all flights leaving the three NYC-area international airports are less than 2 hours, or 120 minutes, in length? Provide a 95% level of confidence on your estimate.
(g) Compute the sampling weight of each flight chosen from each of the three NYC-area airports: wEW R, wJF K ,
and wLGA. Interpret the meaning of each of these weights.
(h) Suppose you wished to sample the number of domestic flights from each of the three airports such
that each flight sampled represented 100 flights departing each airport. How many domestic flights
from each of the three NYC-area airports would you sample?
