A certain characteristic in a large population has a distribution that is symmetric about the mean m. 60 percent of the distribution lies within one standard deviation d of the mean. If the shelf’s average life is 7.2 years and the standard deviation is 2.8 years, what percent of the distribution has more than 10.0 years as a shelf’s average life? Choose the correct choice from the following answers:
A) 10%
B) 12%
C) 14%
D) 15%
E) 17%
Average = 7.2   SD = 2.8   7.2 - 2.8 &lt; 60% of distribution &lt; 7.2 + 2.8   4.4 &lt; 60% of distribution &lt; 10.0   30% is outside this range.   Given: Distribution is symmetric. So 15% of distribution is less than 7.5 and the other 15% of distribution is greater than 10.0.   Answer: 15%
<result>D</result>
A certain characteristic in a large population has a distribution that is symmetric about the mean m. 60 percent of the distribution lies within one standard deviation d of the mean. If the shelf’s average life is 7.2 years and the standard deviation is 2.8 years, what percent of the distribution has more than 10.0 years as a shelf’s average life?