Question

A car company advertises that its new “ultra-green” cars get an average of at least 100 miles per gallon (mpg) in fuel efficiency. The mpg readings are known to be normally-distributed. The mpg readings for 30 such cars are shown in the table below. The mean for these 30 cars is 97.5 mpg, and the standard deviation is 10.4675 mpg. (You do not need to calculate these numbers from the table below.)

Dataset of numbers: 97 117 83 79 97 87 78 93 94 96 102 98 82 96 113 113 111 90 101 99 112 89 92 96 98 99 101 115 92 105

Estimate the mean mpg of all ultra-green cars with 90% confidence.

Answers:

(a) (92.58, 102.42) (b) (93.59, 101.41) (c) (94.25, 100.75) (d) (94.31, 100.69) (e) (96.93, 98.07)

Answer 1