In a study of exercise, a large group of male runners walk on a treadmill for 6 minutes.
Their heart rates in beats per minute at the end vary from runner to runner according to the N(104, 12.5) distribution.
The heart rates for male nonrunners after the same exercise have the N(130, 17) distribution. What percent of the runners have heart rate above 130? What percent of the non-runners have rates above 130?

Question

In a study of exercise, a large group of male runners walk on a treadmill for 6 minutes.
Their heart rates in beats per minute at the end vary from runner to runner according to the N(104, 12.5) distribution.
The heart rates for male nonrunners after the same exercise have the N(130, 17) distribution. What percent of the runners have heart rate above 130? What percent of the non-runners have rates above 130?

anonymous · Answer

50% of non runners have rates above 130 since that is the mean for non runners. Right?

anonymous · Answer

For runners, their mean is 104, so we do 130-105 to get the difference, and see how many standard deviations there are in that difference: 25/12.5 = ? And then you can find a number in your textbook that says how many in a population are included within certain standard deviations from the mean.

anonymous · Answer

http://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule