Certain event
A certain event is an event that must happen in a given experiment.
Practice This ConceptMain explanation
Teacher explanation
If an event always happens, its probability is 1. For example, when one standard die is thrown, getting a number less than 7 is certain because every face is less than 7. Students should connect certainty with full sample-space coverage, not with one special outcome.
Example
When a standard die is thrown once, getting a number less than 7 is a certain event.
Simple analogy
All outcomes help the event happen, so probability is 1.
Common confusion
Students sometimes think probability 1 means one outcome only, instead of an event that always happens.
Exam tip
If every outcome in the sample space supports the event, the probability is 1.
Answer writing and exam use
1-mark use
Write the exact meaning of certain event in one clean line.
2-mark use
Define certain event and add one example or condition.
3-mark use
Explain certain event, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.
Help improve this page
Found something confusing, incorrect, or missing?