Departures 2016. What are the chances your f light will leave on time? The U.S. Bureau of Transportation Statistics of the Department of Transportation publishes information about airline performance. Here are a histogram and summary statistics for the percentage of f lights departing on time each month from 1995 through November 2016. (Data in Late arrivals 2016)

There is no evidence of a trend over time. (The correlation of % On-Time Departure with time is r = -0.073.)

a) Check the assumptions and conditions for inference.

b) Find a 90% confidence interval for the mean percentage of f lights that depart on time.

c) Interpret this interval for a traveler planning to f ly.

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# of Months T 30 30 20- 10 65 70 75 80 85 90 % On-Time Departures 263 y 80.72 S 4.57