Probability
Fractions, decimals and percentages of chance.
Weather forecasts
A forecast says “70% chance of rain”. That is a probability of 0.7. The chance of no rain is 30%, or 0.3.
Fractions, decimals, percentages
There are 8 equal sections. P(red) = 3/8 = 0.375 = 37.5%. P(not red) = 1 − 3/8 = 5/8.
Sample spaces
List all outcomes in a sample space. Two coins: HH, HT, TH, TT. P(one head and one tail) = 2/4 = ½.
Two dice
There are 6 × 6 = 36 outcomes. A total of 7 appears 6 times: P(7) = 6/36 = ⅙. A total of 2 appears once: P(2) = 1/36.
Can both happen?
Some events cannot happen at the same time: one spin cannot be red and blue. Other events can: a dice can show an even number and a number greater than 3 (4 or 6). Probability can be written from 0 to 1 or from 0% to 100%.
What I learnt
- I can express probability as a fraction, decimal or percentage.
- I can list sample spaces.
- I can use P(not A) = 1 − P(A).