A wheel with known odds
This wheel is not fair, and that is the point. Sunny has four tenths of the circle, cloudy three, rain two and snow one – so the class knows what should happen before anybody spins. Press SPIN!:
The list shows each outcome as a percentage, which is the prediction:
The lesson
- Read the percentages off the list and write them on the board: 40, 30, 20, 10.
- Ask what ten spins will look like. Most children say four, three, two and one.
- Spin ten times and compare. It is never that tidy.
- Spin a hundred times, in pairs, and look again. Now it is close.
- Ask why – and you have taught the law of large numbers without saying it.
Counter does the counting for you: every outcome, how often it came up, its share of the spins so far, and the share it should have:
Change the odds and predict again
Rewrite the weights and the wheel is a different experiment. A wet climate is 🌧️|Rain|x5; an equal wheel is every line without a number, and the class can test that four outcomes really do come out at 25 per cent each:
Other experiments on the same wheel
- A weather forecast: what is the chance of two rainy days in a row?
- A loaded die – six weights, one of them heavier.
- A bag of marbles: six red, three blue, one gold.
- Comparing a hundred spins by one pair with the whole class’s thousand.
Everything is counted on the pupil’s own device, so each pair has their own numbers to bring to the board. Count again starts the next experiment.