Question 1
Apply the 68-95-99.7 rule to answer the question.
The lifetimes of light bulbs of a particular type are normally distributed with a mean of 310 hours and a standard deviation of 9 hours. What percentage of the bulbs have lifetimes that lie within 2 standard deviations to either side of the mean?
◦ 95%
◦ 99.7%
◦ 68%
◦ 98%
Question 2
Apply the 68-95-99.7 rule to answer the question.
The systolic blood pressure of a group of 18-year-old women is normally distributed with a mean of
and a standard deviation of 13 mmHg. What percentage of 18-year-old women in this group have a systolic blood pressure that lies within 3 standard deviations to either side of the mean?
◦ 95%
◦ 34%
◦ 68%
◦ 99.7%