Suppose that a the normal rate of infection for a certaindisease in cattle is 25%.
To test a new serum which may prevent infection, three experimentsare carried out. The
test for infection is not always valid for some particular cattle,so the experimental results are
“inconclusive†to some degree–we cannot always tell whether a cowis infected or not. The
results of the three experiments are
(a) 10 animals are injected; all 10 remain free frominfection.
(b) 17 animals are injected; more than 15 remain free frominfection and there are two doubtful
cases.
(c) 23 animals are infected; more than 20 remain free frominfection and there are three
doubtful cases.
Which experiment provides the strongest evidence in favour of theserum? Explain your answer.
