DataSciencester’s VP of Talent has interviewed a number of job candidates from the site, with varying degrees of success. He’s collected a dataset consisting of several (qualitative) attributes of each candidate, as well as whether that candidate interviewed well or poorly. Could you, he asks, use this data to build a model identifying which candidates will interview well, so that he doesn’t have to waste time conducting interviews?
This seems like a good fit for a decision tree, another predictive modeling tool in the data scientist’s kit.
What Is a Decision Tree?
A decision tree uses a tree structure to represent a number of possible decision paths and an outcome for each path.
If you have ever played the game Twenty Questions, then you are familiar with decision trees. For example:
“I am thinking of an animal.”
“Does it have more than five legs?”
“No.”
“Is it delicious?”
“No.”
“Does it appear on the back of the Australian five-cent coin?”
“Yes.”
“Is it an echidna?”
“Yes, it is!”
This corresponds to the path:
“Not more than 5 legs” → “Not delicious” → “On the 5-cent coin” → “Echidna!”
in an idiosyncratic (and not very comprehensive) “guess the animal” decision tree (Figure 17-1).
Figure 17-1. A “guess the animal” decision tree
Decision trees have a lot to recommend them. They’re ...
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