Unknown Attribute Values

What if some examples missing values of A?

Use training example anyway, sort through tree

• If node n tests A, assign most common value of A among other examples sorted to node n

• assign most common value of A among other examples with same target value

• assign probability p_i to each possible value v_i of A
  • assign fraction p_i of example to each descendant in tree

Classify new examples in same fashion