DISCUSSION (CONT.)

• Pruning

  
  

  • Pruning on average produces better results on both problems

    
    

  • Pruning seems to produce a greater improvement on systems using continuous attributes (USFS) than systems using discrete attributes (surname)

    
    

  • Pessimistic pruning usually prefers not to prune a subtree

    
    

• Confidence limit

  
  

  • Using the default 25% confidence limit, the trees for both problems were not pruned

    
    

  • Most pruning occurs when the confidence limit is less than 15%