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Class 9 Maths — Probability from experiments

Work out the empirical probability of an event from the results a trial actually gave.

Name: ________________________

Before you start

Every probability there has ever been lives somewhere on this line. Move along it and read off the values.

0.00.51.0

Zero means it never happened and one means it happened every single time. Nothing sits outside the two ends — a probability of 1.4 or of -0.2 is not unlikely, it is impossible.

  1. 1.A batch of 50 bulbs was tested and 3 of them were faulty. What is the empirical probability that a bulb is faulty? Give your answer as a decimal.

  2. 2.Sort each number by whether it could possibly be a probability.

    Groups: Could be a probability · Could not be a probability

    • -0.2
    • 7/5
    • 0
    • 1
    • 0.25
    • 1.4

  3. 3.In a trial, seeds germinated with an empirical probability of 0.8. Out of 500 more seeds, how many would you expect to germinate?

  4. 4.Over 200 school days a bus was late on 30 of them. What is the empirical probability that it is late? Give your answer as a decimal.

  5. 5.A die was rolled 120 times. Match each result to its empirical probability, written as a fraction.

    • A six came up 20 times
    • An even number came up 66 times
    • A one came up 15 times
    • A number above 4 came up 42 times
    • 66/120
    • 42/120
    • 15/120
    • 20/120

  6. 6.An event has an empirical probability of 0.7. Tap where that sits on the probability line.

    Mark the line with an X.

    0.00.51.0

  7. 7.A coin is tossed 100 times and lands heads 54 times. What is the empirical probability of a tail? Give your answer as a fraction.

  8. 8.A coin gives 7 heads in 10 tosses, and 503 heads in 1000 tosses. Which empirical probability is closer to the theoretical one half?

    • a) Neither is anywhere near
    • b) The one from 1000 tosses
    • c) The one from 10 tosses
    • d) They are exactly as close as each other

Answer key — Class 9 Maths — Probability from experiments

  1. 1. 0.06
  2. 2. 0.25 → Could be a probability; 1.4 → Could not be a probability; 0 → Could be a probability; -0.2 → Could not be a probability; 1 → Could be a probability; 7/5 → Could not be a probability
  3. 3. 400
  4. 4. 0.15
  5. 5. A six came up 20 times → 20/120; An even number came up 66 times → 66/120; A one came up 15 times → 15/120; A number above 4 came up 42 times → 42/120
  6. 6. 0.7
  7. 7. 46/100
  8. 8. b) The one from 1000 tosses