Probability 100% 50% 0% 1 0.5 ½ Will happen Won’t happen e.g throw a normal dice and score between 1 and 6 Won’t happen e.g throw a normal dice and score 7 0.5 ½ Equally likely to happen or not e.g throw a normal dice and score an even number

If all the possible outcomes are equally likely P(something happening) = e.g. On a normal dice P(throw a number less than 3) = Always simplify a probability fraction if you can.

If you are finding the probability of two things which do not depend on each other you can use a 2 way diagram. e.g Find the probability of getting heads on a coin and an odd number on a dice. Possible outcomes for dice 1 2 3 4 5 6 H H 1 H 2 H 3 H 4 H 5 H 6 T T 1 T 2 T 3 T 4 T 5 T 6 1 2 3 4 5 6 H T Possible outcomes for coin

You can calculate almost any probability with a tree diagram Find the probability of getting two heads and one tail in 3 flips.

Comparing probabilities With a calculator you can: Compare probabilities as a decimal 3÷5 = 0.6 etc Compare probabilities as a percentage 3÷5 x 100 = 60% Without a calculator you must make them into equivalent fractions

Using probabilities to make predictions Once you have a probability you can make a prediction e.g 1) the probability of getting a head with a coin toss is ½ Toss a coin 30 times expect heads ½ x 30 times = 15 times 2) probability of throwing a 7 on two dice is Throw two dice 30 times expect heads 1÷6 x 30 times = 5 times