Q. Suppose on performing reduced error pruning, we collapsed a node and observed an improvement in the prediction accuracy on the validation set.
Which among the following statements are possible in light of the performance improvement observed?
(a) The collapsed node helped overcome the effect of one or more noise affected data points in the training set
(b) The validation set had one or more noise affected data points in the region corresponding to the collapsed node
(c) The validation set did not have any data points along at least one of the collapsed branches
(d) The validation set did have data points adversely affected by the collapsed node

• (A) a and b
• (B) a and d
• (C) b, c and d
• (D) all of the above