




















• 
A
“complementary” prior is defined


as one that
exactly cancels the



correlations
created by explaining



away. So the
posterior factors.




– 
Under
what conditions do



complementary
priors exist?




– 
Complementary
priors do not



exist
in general:




• 
Parameter counting shows that



complementary
priors cannot exist



if the
relationship between the



hidden
variables and the data is



defined
by a separate conditional



probability
table for each hidden



configuration.

