Change the stimulus to read: Edward Jenner? ’s smallpox inoculation experiment was based on his observation that dairymaids who had had cowpox did not contract smallpox. How did Jenner form his hypothesis from this observation? He asked what would happen if he inoculated a person with cowpox fluid and then later with smallpox fluid. He tested different existing inoculations to see which one was most effective in preventing smallpox. He observed dairymaids who had contracted cowpox to see whether they became immune to smallpox. He drew a conclusion about dairymaids who got cowpox becoming immune to getting smallpox.