Question

A manufacturer knows that their items have a normally distributed lifespan, with a mean of 11.5 years, and standard deviation of 1.9 years.

If you randomly purchase one item, what is the probability it will last longer than 12 years?

Answer 1

39.74 %

Explanation:

12 years - 11.5 = .5 years

.5 / 1.9 = .2631 S.D above the mean

From z-score table this corresponds to .6026

60.26 are BELOW this life span

39.74 % are above 12 years