EXAMPLE 6 Do angry people have a greater incidence of heart disease?
People who get angry easily tend to have more heart disease. That’s the conclusion of a study that followed a random sample of 12,986 people from three locations for about four years. All subjects were free of heart disease at the beginning of the study. The subjects took the Spielberger Trait Anger Scale test, which measures how prone a person is to sudden anger. Here are data for the 8474 people in the sample who had normal blood pressure. CHD stands for “coronary heart disease.’’ This includes people who had heart attacks and those who needed medical treatment for heart disease.
582
| Anger Score | |||
| Low | Moderate | High | |
| Sample size | 3110 | 4731 | 633 |
| CHD count | 53 | 110 | 27 |
| CHD percent | 1.7% | 2.3% | 4.3% |
There is a clear