Idea 14of 22Builds onTally the spins
What should happen and what did happen
Why don't real spins match the probability exactly?
Today you'll discover
- where each kind of probability comes from
- how to write the experimental one
- why they differ
Think firstExpected 5 orange; the spins gave 6
Theory says 1/4 of 20 spins: 5 orange. The spins gave 6. Is something wrong?
Decide first, then press Next. Ask where each fraction came from.
A small spinner, one quarter orange, a prediction of 5 orange in 20 spins, and a tally table showing 6 orange and 14 blue. Along the bottom: theoretical 1/4 = 5/20 and experimental 6/20, then expected 5, got 6: 1 apart. The last step shows a 3/8-orange spinner spun 40 times.
See the whole ideathe big idea and the key word, in one place
The big idea
Theoretical probability says what should happen; experimental probability says what did happen in the trials.
Compare themTheoretical: from the spinner, before any spins (1/4). Experimental: from the results, after spinning (6 orange of 20 spins: 6/20).
Easy to get wrongAn experiment does not change the theory. The spinner is still 1/4 orange after it gives 6/20.
Key words
- theoretical probability
- what should happen, worked out from the outcomes before any trials
- experimental probability
- what did happen: the count of the event over the number of trials
Ready to use it?
- Find the experimental probability from a tally.
- Compare it with the theoretical probability.