Fighting cancer. Congress wants the medical establishment to show that progress is being made in fighting cancer. Here are some variables that might be used:

1. Total deaths from cancer. These have risen sharply over time, from 331,000 in 1970, to 505,000 in 1990, and to 553,888 in 2004.

2. The percentage of all Americans who die from cancer. The percentage of deaths due to cancer rose steadily, from 17.2% in 1970 to 23.5% in 1990, then leveled off to 23.1% in 2004.

3. The percentage of cancer patients who survive for 5 years from the time the disease was discovered. These rates are rising slowly. For whites, the 5-year survival rate was 50.3% in the 1974 to 1976 period and 64.1% from 1995 to 2000.

None of these variables is fully valid as a measure of the effectiveness of cancer treatment. Explain why Variables 1 and 2 could increase even if treatment is getting more effective, and why Variable 3 could increase even if treatment is getting less effective.

AppendixLO1