A random sample of 81 Automobiles traveling on a section of an interstate showed an average speed of 60 mph. The distribution of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph.
Question 1.) If we are interested in determining an interval estimate for μ at 86.9% confidence, the z value to use is?
a.) 1.96
b.) 1.31
c.) 1.51
d.) 2.00