The Probability Scale
Understand probability as a measure on a scale from 0 (impossible) to 1 (certain); use the language of probability including likely, unlikely, certain, and impossible
What a learner can do afterwards
- Place everyday events on a 0-to-1 probability scale with justification
- Explain why a fair six-sided die gives each number a probability of 1/6
- Distinguish between equally likely outcomes (fair coin) and unequally likely outcomes (biased spinner)
The lesson
Every event has a chance of happening. We measure that chance with a number called probability. Probability always sits between 0 and 1.
Words help you talk about where an event sits. Near 0, we say unlikely. Right in the middle, we say even chance. Near 1, we say likely.
Compare three events. The sun rising tomorrow is certain, so its probability is 1. Flipping a coin and getting heads is an even chance, so its probability is 1/2. Rolling a 6 on a fair die is less likely, so its probability is only 1/6.
Fair means every outcome has the same probability, like a coin or a normal die. A biased spinner is not fair. Some colors cover more space, so they are more likely to be landed on.
Probability is a number from 0 (impossible) to 1 (certain), and words like unlikely, even chance, and likely tell you where an event sits on that scale.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.