Laser guns for detecting speeders require an accurate measurement of distance. In one daily calibration test, police

Question:

Laser guns for detecting speeders require an accurate measurement of distance. In one daily calibration test, police measure the known distances 164 feet and 104 feet. The difference in readings should be 60 but there is some variation. The differences (courtesy of Madison Police Department) for ten guns are

(a) Do the data provide strong evidence that the mean difference is not equal to 60 feet?
(b) Construct a 95% confidence interval for the mean difference.
(c) Check that all of the values for mean distance in the confidence interval, as well as all ten observations, are less than 1 percent of the exact 60 feet. Laser guns are much more accurate than the old radar guns.