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WA7. Classification Trees

Statement

Using figure 22.6 classification tree construct a similar tree depicting each class of grades from the course grading scale from A to F. Identify the classification of your preferred class grade on your grade tree.

Solution

  • The classification tree that is included in this text represents the course grading scale from A to F according to the table below (UoPeople, 2023).
Letter Grade Grade Scale Grade Points
A+ 98 - 100 4.00
A 93 - 97 4.00
A- 90 - 92 3.67
B+ 88 - 89 3.33
B 83 - 87 3.00
B- 80 - 82 2.67
C+ 78 - 79 2.33
C 73 - 77 2.00
C- 70 - 72 1.7
D+ 68 - 69 1.3
D 63 - 67 1.00
D- 60 - 62 0.67
F 0 - 59 0.00
  • The classification tree expects a numeric value as input. The numeric value is the grade scale which belongs to the [0, 100] interval. The classification tree will return the letter grade that corresponds to the numeric value.
  • The found letter grade can then be used to determine the grade points that correspond to the letter grade according to the table above.
  • The classification tree is shown below.

Classification Decision Trees

  • The classification process always starts at the root node, then goes left to right and top to bottom, and ends at a leaf node.
  • The classification tree picks up the first node from the list that satisfies the condition (printed over the lines) and then continues within the level below.
  • Example grade 82:
    • The grade enters the classification tree at the root node, it is being checked against the condition >= 90 which is not satisfied.
    • It then goes to the next node (to the left), which is the node >= 80 and it is satisfied.
    • The classification process then moves down one level through the B node (other conditions to the left are skipped).
    • On the next level, the grade is checked against the condition >= 88 then >= 83, and finally >= 80 which is satisfied.
    • The classification process then moves down one level through the B- node.
    • The final node is a leaf node and it returns the letter grade B-.
    • According to the table above, the grade points for the letter grade B- are 2.67.

Conclusion

  • The classification tree is a decision tree that is used for classification problems.
  • It may seem complicated at first, but it is actually very simple to use and gives more details visually than the table does.
  • The direction or how to navigate through the tree may be different from tree to tree, so it is important to understand the tree’s structure and how it works, looking for any notes or instructions that may be included with the tree.

References