=+38. Fuel economy. A bus company suffering losses for several months would like to find ways to make profits. In order to reduce fuel costs, the company hired a research firm to study the optimal speed for their buses to drive. Researchers drove a bus for 200 miles at speeds ranging from 35 to 75 miles per hour. From their data, they created the model Fuel Efficiency = 30 - 0.13 Speed and created this residual plot:

M16_SHAR8696_03_SE_C16.indd 575 14/07/14 7:38 AM 576 CHAPTER 16 Understanding Residuals

–2.5

–2

–1.5

–1

–0.5 0

0.5 1

1.5 18 20 22 24 26 Residuals Fuel Efficiency