In the seventies, Doctors believed that inoculation, which involves exposing a person to the disease in a controlled form, could reduce the likelihood of death. The table below classifies 6224 individuals according to two variables: inoculated and result. The variable inoculated takes two levels: yes or no, indicating whether the person was inoculated to smallpox or not. The variable result takes two levels: lived or died, indicating whether the person lived or died from smallpox.

inoculated result yes no Total lived 238 5136 5374 died 6 844 850 Total 244 5980 6224