---
title: "Short note: supervised vs unsupervised"
subject: "Artificial Intelligence"
chapter: 6
key: "semester_6/artificial_intelligence:supervised-vs-unsupervised-note"
source: https://www.bctengineer.com/q/semester_6/artificial_intelligence/supervised-vs-unsupervised-note
site: BCT Engineering
---

# Short note: supervised vs unsupervised

Artificial Intelligence · Chapter 6: Machine Learning

- Asked in: 2074 Bhadra, 4 marks
- Video: [Supervised vs. Unsupervised Learning](https://www.youtube.com/watch?v=W01tIRP_Rqs) — IBM Technology
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/artificial_intelligence/supervised-vs-unsupervised-note
- Whole chapter: https://www.bctengineer.com/md/semester_6/artificial_intelligence/chapter-6

## Question

Write a short note on supervised versus unsupervised learning.

## Short answer

Supervised learning uses labelled data to predict outputs (e.g., classification), while unsupervised learning finds hidden patterns in unlabelled data (e.g., clustering). Supervised has error feedback; unsupervised has no teacher.

## Answer

**Supervised learning** trains a model on labelled data, where each input has the correct output (target). The model learns the mapping and the error between prediction and target is used to adjust it. Tasks: classification (spam / not spam) and regression (house price). Algorithms: perceptron, back-propagation, decision trees, SVM, k-NN.

**Unsupervised learning** works on unlabelled data. The model finds hidden structure by itself, such as clusters, similarities or lower-dimensional representations. Tasks: clustering, association, dimensionality reduction. Algorithms: k-means, Kohonen SOM, competitive learning, PCA.

| Point | Supervised | Unsupervised |
|---|---|---|
| Data | Labelled | Unlabelled |
| Teacher/feedback | Yes (error signal) | No |
| Goal | Predict output | Discover patterns |
| Accuracy check | Easy, against known labels | Hard, no ground truth |
| Example | Handwritten digit recognition | Customer segmentation |

A third type, **reinforcement learning**, learns from rewards and penalties.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What defines supervised learning?
   A. Finding clusters without labels
   B. Learning only from rewards
   C. Using no feedback at all
   D. Training on labelled data where the error between prediction and target adjusts the model
   Answer: D. Each input has a correct output. (Key point: Supervised)

2. Which is an unsupervised task?
   A. Customer segmentation by clustering
   B. Handwritten digit recognition
   C. House price regression
   D. Spam classification from labels
   Answer: A. Clustering finds structure without labels. (Key point: Unsupervised task)

3. Which algorithm is unsupervised?
   A. Perceptron
   B. k-means
   C. Decision tree
   D. Back-propagation
   Answer: B. k-means, SOM and PCA use no labels. (Key point: Algorithms)

4. What is reinforcement learning?
   A. Learning from labelled examples
   B. Learning from clusters
   C. Learning from rewards and penalties
   D. Learning from a fixed rule table
   Answer: C. It is the third type besides supervised and unsupervised. (Key point: Third type)

## Related in Artificial Intelligence

- [Neural network; supervised vs unsupervised](https://www.bctengineer.com/question.md?key=semester_6%2Fartificial_intelligence%3Ann-supervised-unsupervised) — Artificial Intelligence, chapter 6
- [GA vs fuzzy based learning](https://www.bctengineer.com/question.md?key=semester_6%2Fartificial_intelligence%3Aga-vs-fuzzy-learning) — Artificial Intelligence, chapter 6
- [Analogy vs inductive learning](https://www.bctengineer.com/question.md?key=semester_6%2Fartificial_intelligence%3Aanalogy-vs-inductive-learning) — Artificial Intelligence, chapter 6
- [Knowledge vs learning, acting humanly](https://www.bctengineer.com/question.md?key=semester_6%2Fartificial_intelligence%3Aknowledge-vs-learning-acting-humanly) — Artificial Intelligence, chapter 1

## Related in other subjects

- [Supervised vs unsupervised learning](https://www.bctengineer.com/question.md?key=semester_7%2Fdata_mining%3Asupervised-vs-unsupervised) — Data Mining, chapter 3