Hi all
A friend of mine is planning to conduct a vacine trial on calves with three
arms ( Low dose, high dose, and placebo). From previous information one
say that the protective effect of low dose is above 70%, that of high dose
is above 30% and that of placebo is about 0% ( probably one might say very
small number like < 5%). This friend like to be 95% confident with final
estimates with 90% power.
We like to know resonable sample size to do the study.
I personaly advised him to use sample size formula for comparison of two
proportions ( taking low and high doses as target values); also I compared
low dose with placebo. The end result was about 17 calves in the two doses
each and 7 calves in placebo.
The main reason for the reduced sample size was high cost of maintaing the
calves for about 2 years.
Thank you all in advance
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