For a good discussion of the names and different types of exhibition
evaluation, read Uses of Evaluation Before, During and After Exhibit Design,
by C.G. Screven, in ILVS Review: A Journal of Visitor Behavior, Vol.1, No. 2,
Spring 1990.
Evaluation done after the exhibition opens is called summative evaluation.
 Exit interviews and audience surveys are two different summative evaluation
methods.  There are others.