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 9.79 41.9 1.32 -51 -11 0 19 437 (a) What is the sample mean difference in actual and expected arrival times? What is the standard deviation of the differences? X = 9.79 (already answered this part correctly) S = 41.9 (already answered this part correctly) (b) Based on the computer output, is it safe to assume this sample is normally distributed? Yes (already answered this part correctly) (c) Can we proceed using the t distribution to build a confidence interval for this mean? Yes (already answered this part correctly) 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. Round your answers to two decimal places. The 95%confidence interval is_______ to ______
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
|
N |
|
StDev |
SE Mean |
Min |
Q1 |
|
Q3 |
Max |
|
1000 |
9.79 |
41.9 |
1.32 |
-51 |
-11 |
0 |
19 |
437 |
(a) What is the sample mean difference in actual and expected arrival times? What is the standard deviation of the differences?
X = 9.79 (already answered this part correctly)
S = 41.9 (already answered this part correctly)
(b) Based on the computer output, is it safe to assume this sample is
(c) Can we proceed using the t distribution to build a confidence interval for this mean? Yes (already answered this part correctly)
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.
Round your answers to two decimal places.
The 95%confidence interval is_______ to _______
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