Oil field pipes are internally coated in order to prevent corrosion. Researchers at a university investigated the influence that coating may have on the surface roughness of oil field pipes. A scanning probe instrument was used to measure the surface roughness of each section in a sample of 10 sections of coated interior pipe. The data(in micrometers) are shown in the table to the right. A Minitab analysis of the data is given below. Complete parts a and b.

One-Sample T: ROUGH

ROUGH variable

10 N

1.93200 mean

0.46523 stdev

0.14712 SE mean

(1.59919, 2.26481) %95 CI

1.772.51

2.351.08

1.482.18

2.111.98

2.371.49

a. Locate a95% confidence interval for the mean surface roughness of coated interior pipe on the accompanying Minitab printout.

( ), ( ) ?

,

(Type integers or adecimals.)

b. Would you expect the average surface roughness to be as high as 2.5micrometers? Explain.

A.

No, because we can be95% confident that the mean surface roughness lies between the lower and upper bounds of theinterval, and 2.5 lies outside the interval.

B.

Yes, because we can be95% confident that the mean surface roughness lies outside the lower and upper bounds of theinterval, and 2.5 lies within the interval.

C.

Yes, because we can be95% confident that the mean surface roughness lies outside the lower and upper bounds of theinterval, and 2.5 lies outside the interval.

D.

Yes, because we can be95% confident that the mean surface roughness lies between the lower and upper bounds of theinterval, and 2.5 lies within the interval.