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