6.110 United Flights in December In Exercise 4.142 we look at a random sample of 1000 United flights in the month of December comparing the actual arrival time to the scheduled arrival time. Computer output (based on the data in DecemberFlights) of the descriptive statistics for the difference in actual and expected arrival time of these 1000 flights is shown below. N Mean StDev SE Mean Min Q1 Median Q3 Max 1000 4.21 45-34 1.43 -51 -15 -5 8 872 a. What is the sample mean difference in actual and expected arrival times? What is the standard deviation of the differences? b. Based on the computer output, is it safe to assume this sample is normally distributed? Why or why not? c. Can we proceed using the t distribution to build a confidence interval for this mean? Why or why not? d. Regardless of your answer to part (c), use the summary statistics to compute a 95% confidence interval for the average difference in actual and scheduled arrival times on United flights in December. e. Interpret the confidence interval you found in part (d) in context