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 of the descriptive statistics for the difference in actual and expected arrival time of these 1000 flights are shown below. N Mean StDev SE Mean Min Q1 Median Q3 Max 1000 4.15 44.5 1.41 -42 -15 -5 7 859

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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 of the descriptive statistics for the difference in actual and expected arrival time of these 1000 flights are shown below.

N Mean StDev SE Mean Min Q1 Median Q3 Max
1000 4.15 44.5 1.41 -42 -15 -5 7 859
 
 

(a) What is the sample mean difference in actual and expected arrival times? What is the standard deviation of the differences?



Enter the exact answers.

x⎯⎯=x¯= Enter your answer in accordance to item (a) of the question statement

s=s= Enter your answer in accordance to item (a) of the question statement
 
(b) Based on the computer output, is it safe to assume this sample is normally distributed?

Yes
No


 
 
(c) Can we proceed using the t distribution to build a confidence interval for this mean?

Yes
No

(d) Regardless of your answer to part (c), use the summary statistics to compute a 95%95% confidence interval for the average difference in actual and scheduled arrival times on United flights in December.

Round your answers to two decimal places.

The 95%95% confidence interval is Enter your answer in accordance to item (c) of the question statement to Enter your answer in accordance to item (c) of the question statement .

 
 

(e) Interpret the confidence interval you found in part (d) in context. Round to two decimal places.

We are 95% confident that the average actual arrival times for United flights in December is between  and  minutes later than the average scheduled arrival time.

 
 
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