Build Your First ClassifierClassification & Decision Trees
Understand how Machine Learning models sort items into categories. Build a step-by-step decision tree flowchart!
Build Your First Classifier
Sorting things into categories
A classifier is an AI model that sorts input data into distinct categories (classes). Instead of predicting a continuous number, a classifier answers: "Which group does this item belong to?"
💡 Interactive Classifier Demonstration (Input ➔ Classifier ➔ Category)
Click any example below to see how a classifier categorizes it:
Type: Binary Classifier. Correct! A classifier takes measurable inputs and sorts them into target categories.
Classification Types
Binary vs Multi-class
Binary Classification
Exactly 2 possible output categories (e.g. Yes/No, Spam/Safe, Pass/Fail).
Multi-class Classification
3 or more output categories (e.g. Cat vs Dog vs Bird vs Fish).
Key Distinction: Classifiers output category labels (like 'Dog' or 'Cat'). If a model predicts a numerical measurement (like house price £250,000), that is called Regression!
🎯 Interactive Activity: Classify as Binary or Multi-class
Select the correct classification type for each task below:
"Is this email spam or not spam?"
"Which animal is this? (Cat, Dog, or Bird)"
"Is the patient healthy or sick?"
"Which grade did student receive? (A, B, C, D, or F)"
Decision Trees
Flowchart Decision Logic
A Decision Tree is a popular classifier that functions like a step-by-step flowchart of Yes/No questions:
1. Root / Internal Node
A question testing a feature (e.g. "Does it have wings?").
2. Branch
The path followed based on the answer (YES or NO).
3. Leaf Node
The final predicted class category (e.g. "Bird").
🌿 Interactive Decision Tree: Follow the Branch
Answer the questions below to trace the decision tree path to a final prediction:
Does the animal have wings?
Playground: Decision Tree Builder
Sort Animals into Birds vs Mammals
Build a decision tree step-by-step to classify animals (Eagle, Penguin, Dolphin, Dog) into Bird vs Mammal:
Target Dataset:
Interactive Exercises
Exercise 1: Classification vs Regression
+15 XP · BeginnerExercise 2: Tree Nodes
+20 XP · BeginnerExercise 3: Binary or Multi-class?
+25 XP · IntermediateExercise 4: Decision Logic
+30 XP · IntermediateKnowledge Check
Ready to test your knowledge?
Answer 10 multiple-choice questions to test your understanding of classifiers and decision trees!
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