Question

Two men, A and B, who usually commute to work together decide to conduct an experiment to see whether one route is faster than the other. The men feel that their driving habits are approximately the same, so each morning for two weeks one driver is assigned to route I and the other to route II. The times, recorded to the nearest minute, are shown in the following table. Using this data, find the 80% confidence interval for the true mean difference between the average travel time for route I and the average travel time for route II. Let d=(route I travel time)?(route II travel time) . Assume that the populations of travel times are normally distributed for both routes.

Day M Tu W Th F M Tu W Th F Route I 32 31 29 29 30 35 31 28 34 28

Route II 30 28 33 32 26 32 26 27 33 24

Step 3 of 4: Find the standard deviation of the paired differences to be used in constructing the confidence interval. Round your answer to one decimal place.

Step 4 of 4: Construct the 80% confidence interval. Round your answers to one decimal place.

Answer 1

step 3:

std deviation =3.0

4)

for 80% CI; and 9 degree of freedom, value of t=			1.383
therefore confidence interval=		sample mean -/+ t*std error
margin of errror          =t*std error=		1.312
lower confidence limit                     =		0.3
upper confidence limit                    =		2.9

from above   80% confidence interval =0.3 ; 2.9