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Probability

Probability. Understand the vocabulary and ideas of probability. Understand and use a probability scale. Calculate the probability of an event occurring. Probability Vocabulary. Put these words in order of likeliness. Unlikely. Impossible. Equally likely. Certain. Likely.

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Probability

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  1. Probability Understand the vocabulary and ideas of probability. Understand and use a probability scale. Calculate the probability of an event occurring.

  2. Probability Vocabulary Put these words in order of likeliness Unlikely Impossible Equally likely Certain Likely

  3. Probability Vocabulary We put the words on a probability scale Impossible Equally likely Certain Unlikely Likely

  4. Where would you place these statements on a probability scale? Impossible Certain A coin lands Heads side up Next year will have 54 Fridays The day after Monday will be Tuesday You will watch TV tonight It will rain in London in the first week of July A new born baby will be a girl

  5. What about these events? Impossible Certain You will be injured next time you play in a sports game A road accident will occur if the road is icy A road accident will occur in normal driving conditions A cyclone will occur in England A man will die before the age of 70

  6. Rather than using words we use numbers on the probability scale Impossible Certain 0 0.5 1 The probability of an event occurring is written as a fraction, a decimal or a percentage, e.g.The probability of getting an even number on rolling a dice is ½ or 0.5 or 50%

  7. How likely? • To find the probability of an event occurring, work out how many things (called outcomes) could happen. • Count how many of them give you the required event • Write these numbers as a fraction:Number of ways it happens Number of things that can happen

  8. How likely? Number of ways it happensNumber of things that can happen The probability of getting an even number when a die (the singular of dice) is rolled: P(even number) = 3 6 (or ½ or 50% or 0.5) NEVER use ratios for probability. P(an event) means the probability of it happening.

  9. Rolling a fair 6 sided die Calculate the probability of rolling: • a 5 • an odd number • a prime number • zero • a number between 0 and 7 • a number greater than 2 1/6 3/6 = ½ 3/6 = ½ 0 1 4/6 = 2/3

  10. What’s the probability that … • a letter chosen from all your names is a vowel? • a pupil picked at random from the class is in your tutor group? • a person’s birthday is on a Sunday this year? • a blue Smartie will be picked out at random from a tube?

  11. From a normal pack of cards, what’s the probability that you choose… 9/13 3/13 6/13 3/13 6/13 ¼ 1/26 1/52 • A number card (2 to 10)? • A face card (jack, queen or king)? • A prime number (let a Jack = 11, King = 13)? • A square number (let the Ace = 1)? • Less than 7 (let the Ace = 1)? • A Diamond? • A red Jack? • The Queen of Spades?

  12. Newspapers • A newsagent delivers these papers – one to each house: • Sun 250 Times 120 • Mirror 300 Mail 100 • Telegraph 150 Express 80 What is the probability that a house picked at random has: The Times? The Mailor the Express? Neither the Sunnor the Mirror? 120/1000 = 0.12 (100+80)/1000 = 0.18 (1000-250-300)/1000 = 0.45

  13. 26 23 20 1 6 16 12 5 17 4 19 22 14 8 28 29 11 10 30 2 9 27 7 18 21 15 3 13 25 24 Roulette P(odd number) P(1 to 10) P(Black) P(number 1) = 15/30 = ½ or 50% = 10/30 = 1/3 or 33% = 15/30 = ½ or 50% = 1/30 or 3.3%

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