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• Decision Node: Dividing a node further into another level sub-node.
           • 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.



                         Task                                                                 Subject Enrichment




             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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