DEVELOPMENT OF A MODEL CASE
Once the critical attnbutes bave been defined. Walker &
Avant (1988) suggest progress to the formulation of a
model case A model case serves to provide evidence of
what the concept defimtely is It should include all the
cnbcal attnhutes The model case shown below received
careful considerabon and tesbng on colleagues and
pabents, as suggested by Walker & Avant (1988) in order
to refine tbe case to its purest form