 # Probability Learning Objective: To be able to understand probability and measure the probability of an event not happening YOU MUST Be able to know how.

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Probability Learning Objective: To be able to understand probability and measure the probability of an event not happening YOU MUST Be able to know how to work a probability scale Some should be able to work out probabilities in different situation Some could be able to use experimental probability

The probability scale- RE-Cap from last year The chance of an event happening can be shown on a probability scale. impossiblecertaineven chanceunlikely likely Less likelyMore likely Meeting with King Henry VIII A day of the week starting with a T The next baby born being a boy Getting homework this lesson A square having four right angles

The probability scale –Re-cap from last year We measure probability on a scale from 0 to 1. If an event is impossible or has no probability of occurring then it has a probability of 0. If an event is certain it has a probability of 1. This can be shown on the probability scale as: Probabilities are written as fractions, decimal and, less often, as percentages between 0 and 1. 0½1 impossiblecertaineven chance

The probability of an event not occurring The probability of a factory component being faulty is 0.03. What is the probability of a randomly chosen component not being faulty? P(not faulty) = 1 – 0.03 =0.97 The probability of pulling a picture card out of a full deck of cards is. What is the probability of not pulling out a picture card? 3 13 P(not a picture card) = 1 – = 3 13 10 13

Listing possible outcomes When you roll a fair dice you are equally likely to get one of six possible outcomes: 1 6 1 6 1 6 1 6 1 6 1 6 Since each number on the dice is equally likely the probability of getting any one of the numbers is 1 divided by 6 or. 1 6

Calculating probability What is the probability of the following events? P(tails) = 1 2 P(red) = 1 4 P(7 of ) = 1 52 P(Friday) = 1 7 2) This spinner stopping on the red section? 3) Drawing a seven of hearts from a pack of 52 cards? 4) A baby being born on a Friday? 1) A coin landing tails up?

Calculating probability If the outcomes of an event are equally likely then we can calculate the probability using the formula: Probability of an event = Number of successful outcomes Total number of possible outcomes For example, a bag contains 1 yellow, 3 green, 4 blue and 2 red marbles. What is the probability of pulling a green marble from the bag without looking? P(green) = 3 10 or 0.3 or 30%

Calculating probability – IN your books calculate A fair dice is thrown. What is the probability of getting a)a 2? b)a multiple of 3? c)an odd number? d)a prime number? e)a number bigger than 6? f)an integer? d) P(a prime number) = 3 6 e) P(a number bigger than 6) = f) P(an integer) = 6 6 = 1 = 1 2 0 Don’t write 0 6

The probability of an event not occurring If the probability of an event occurring is p then the probability of it not occurring is 1 – p. The following spinner is spun once: What is the probability of it landing on the yellow sector? P(yellow) = 1 4 What is the probability of it not landing on the yellow sector? P(not yellow) = 3 4

The probability of an event not occurring The probability of a factory component being faulty is 0.03. What is the probability of a randomly chosen component not being faulty? P(not faulty) = 1 – 0.03 =0.97 The probability of pulling a picture card out of a full deck of cards is. What is the probability of not pulling out a picture card? 3 13 P(not a picture card) = 1 – = 3 13 10 13

Class work Framworking 3- Exercise 3b 1-7

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