Missing Attribute Values
Situations
- missing attribute value(s) in the training set
- missing value(s) in the validation or subsequent tests
Quick and dirty methods
- assign it the same value most common for other training examples at the same node
- assign it the same value most common for other training examples at the same node that have the same classification
“Fractional” method
- assign a probability to each value of A based on observed frequencies
- create “fractional cases” with these probabilities
- weight information gain with each case’s fraction