Class 9 Mathematics Chapter 7 The Mathematics of Maybe: Introduction to Probability – Revision Notes

This chapter defines probability the way it’s actually measured in experiments — as the fraction of trials where an event occurs — and covers the key terms like outcome, trial and event that go with it.

Last Updated: September 23, 2026

Key Terms

• Experiment/trial: action with uncertain result.
• Outcome: possible result.
• Event: collection of one or more outcomes.

Empirical Probability

• P(E) = (trials where E happened) / (total trials).
• 0 ≤ P(E) ≤ 1.
• P(E)=0: impossible (in data); P(E)=1: certain (in data).

One-Line Summary

Empirical probability is calculated directly from real experimental/observational data as a fraction (favourable trials/total trials), always falling between 0 and 1, and becomes more reliable as the number of trials increases.

Quick visual: a worked diagram from the full Solutions page, for reference.

Frequently Asked Questions

What is the difference between theoretical and experimental probability?
Theoretical probability is calculated based on logical reasoning about equally likely outcomes before an event occurs, while experimental probability is calculated based on the actual results observed after performing a real experiment or trial.

Why does experimental probability get closer to theoretical probability as the number of trials increases?
As the number of trials increases, random variations tend to average out, so the observed frequency of an outcome approaches its true underlying probability, a pattern connected to the law of large numbers.

Written by Satish

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