What is Gini impurity?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
Gini impurity measures how mixed the classes are inside a node.
WHY — Decision Trees instead of guessing?
Why interviewers care about Decision Trees:
people who only read docs from people who shipped.
and tied to AI / ML work.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Gini impurity measures how
mixed the classes are inside a node.
- 2It is zero for
a pure node and higher when classes are evenly mixed.
- 3Many trees split by
choosing the cut that most reduces Gini.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Gini impurity measures how mixed the classes are inside a node. It is zero for a pure node and higher when classes are evenly mixed.