I agree with Doug--you will notice right away if something is not working
correctly, so a large sample size is not that important.  Formative
evaluation is an iterative process.  Test until you reach what you have set
as the goal for that component.  And if it's too complicated, break it down
and test those subcomponents using the same iterative process.  I enjoy
formative evaluation b/c it is so quick (when compared to other types of
evaluation) and gratifying b/c you see immediate results--unfortunately,
not always positive ones!

Wendy Calvert
Consultant
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