An event is certain when it must happen in every outcome of a described situation, and impossible when it cannot happen in any outcome; these judgments depend on the stated rules and available outcomes. Learners distinguish impossible events from merely unlikely events and certain events from merely likely ones, without assigning numerical probabilities or analyzing more advanced chance models.
An event is certain if it must happen every time.
An event is impossible if it cannot happen at all.
To decide, list or look at all the possible outcomes.
Example: A bag contains only these cards:
You pick one card without looking.
Event: Pick a card.
This is certain because every possible pick is a card.
Event: Pick a triangle.
This is impossible because there is no triangle card in the bag.
Event: Pick a circle.
This is neither certain nor impossible. It can happen, but it does not have to happen.
Remember:
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