Suppose That the Average Life of a Refrigerator Before Replacement $\mu$

Multiple Choice

Suppose that the average life of a refrigerator before replacement is $\mu$ = 14 years with a (99.7% of data) range from 8 to 20 years. Let x = age at which a refrigerator is replaced. Assume that x has a distribution that is approximately normal. Find a good approximation for the standard deviation of x values.

A) 1 year
B) 2 years
C) 4 years
D) 6 years
E) 3 years