Exhibit 8-2
A random sample of 121 automobiles traveling on an interstate showed an average speed of 65 mph. From past information, it is known that the standard deviation of the population is 22 mph.
-Refer to Exhibit 8-2. If we are interested in determining an interval estimate for μ at 96.6% confidence, the Z value to use is
A) 1.96
B) 0.483
C) 2.12
D) 1.645

Question

Quizplus · Accepted Answer

To find the Z value for a 96.6% confidence interval, we first need to find the area in the tails of the normal distribution that corresponds to 1 - 0.966 = 0.034. Using a standard normal table or calculator, we find that the area in one tail is 0.017. To find the corresponding Z value, we look for the value that has an area of 0.017 to its right (since we want the area in the upper tail).

Z = 2.12 (approximate value)

Therefore, the best choice is C.

Exhibit 8-2 A Random Sample of 121 Automobiles Traveling on an Interstate