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• Leaf Node: A node that does not split further.

               • Parent Node: A node that is a level above a sub-node.
               • Child Node: A sub-node that falls under another node.

            Let us understand about decision trees with the help of an example.

                                                           Extracurricular Activities




                                                   Yes                           No




                                 Musical Theatre       Self Defence        Coaching              Tuition



                                                                     Karate
                          Vocals               Dance

                                                            Weight Lifting
                                    Theatre
            Following are some of the important points to consider while designing a decision tree:

               • There can be a possibility of multiple decision trees which lead to correct prediction for a single dataset. The
              simplest one should be chosen.
               • The dataset might contain redundant data at times, which does not have any reference while creating a decision
              tree. Therefore, it is necessary that only those parameters that affect the output directly should be included.
               • While making Decision Trees, one should take a look at the dataset given to them and try to figure out what
              pattern does the output leaf follow. Try selecting any one output and on its basis, find out the common links
              which all the similar outputs have.

                                                                                                    Subject Enrichment
                            Task



                 1.   The following is a dataset comprising 4 parameters which lead to the prediction of a student choosing
                    a Science stream in senior secondary school. Make decision tree for this dataset:

                   Aptitude     Logical Skills  Analytical Skills  Reasoning    Stream Selection: Science
                     High           High             High             High                 Yes
                     High           Low               Low             Low                  No
                      Low           High             High             High                 Yes
                      Low           Low               Low             High                 No
                      Low           High             High             Low                  No

                 2.  Make a decision tree to choose a book from the library based on the following selections.

                    Choice 1: Fiction—Sci-Fi, Mystery, Classics.
                    Choice 2: No Fiction—Travel Diaries, Autobiographies, History, Travelogues.





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