19.

(a) What are the independence assumptions made in the naive Bayes classifier for the help system of Example 8.35.

(b) Are these independence assumptions reasonable? Explain why or why not.

(c) Suppose we have a topic-model network like the one of Figure 8.26, but where all of the topics are parents of all of the words. What are all of the independencies of this model?

(d) Give an example where the topics would not be independent.