A sample of 16 is taken from a population which has a normal distribution with mean 12 and standard deviation 4. The probability that the sample mean is less than 13 is:

a. .1587

b. .6213

c. .8413

d. .9332

An automotive engineer measures fuel consumption on a dynamometer for a prototype car. He records the following data:

SPEED (MPH) MILEAGE (MPG)

40 23

50 21

60 17

He decides that he needs to perform a regression analysis to perdict mileage, and selects speed as the predictor variable and mileage as the response variable. What is the predicited mileage for a speed of 55 mph?

a. 20.33

b. 18.83

c. 17.33

d. 15.83