Chapter 6 
Alternatives to Animal Use 
in Research 
Unless we get a handle on what is happening in the mammalian brain, there’s no way of 
knowing whether any of these [invertebrate] models is right or not. 
Richard F. Thompson 
Stanford University 
Science 85 6(4):33, 1985 
Investigators often ask statisticians how many observations they should make ( fortunately , 
usually before the study begins). To be answerable, this question needs fuller formulation. 
There is a resemblance to the question, How much money should I take when I go on 
vacation? Fuller information is needed there too. How long a vacation? Where? With whom? 
Three questions need to be answered before the sample size is determined. How variable 
are the data that will be collected? How precise an answer is needed? How much 
confidence should there be in the answer obtained? These questions can be well worth 
probing even if the question of sample size will foreseeably be answered by the size of the 
budget or the time available for the study. Sometimes a planned study is dropped because 
sample-size analysis shows that it has almost no chance of providing a useful answer under 
the constraints of time or budget that apply. 
Lincoln E. Moses 
Stanford University 
N. Engl. J. Med. 312:890-897, 1985 
