I got this question but I don't understand what 'weighted entropy' mean here ?
Age is the x-axis and Salary is the y-axis.
Compute the following:
The entropy of the full set of points.
The entropy of the set of points that belong to the left child (those with Salary < 75).
The entropy of the set of points that belong to the right child (those with Salary ≥ 75).
The weighted entropy of the two children.
The decrease in entropy due to this split.