=+31. Smoking. An insurance company would like to offer discounts on its life-insurance policies to nonsmokers.

In a study, they asked 200 randomly selected men who are 60 years old whether they smoke at least one pack of cigarettes per day and if they have ever suffered from M14_SHAR8696_03_SE_C14.indd 500 14/07/14 7:30 AM Exercises 501 heart disease. In the sample, 56 people were smokers, and, of those, 21 people have suffered from a heart disease. Of the 144 nonsmokers, 28 people have suffered from a heart disease.