S3.2.1 Conditional probability and tree diagrams Quiz: Pearson Edexcel Maths, Unit 13

The 20 questions

1. What does the notation P(A|B) represent?

   • Conditional probability
   • Marginal probability
   • Joint probability
   • Independent probability

2. For independent events A and B, what is P(A|B) equal to?

   • P(A) + P(B)
   • P(A)
   • 0
   • P(B)

3. Which formula correctly defines the conditional probability P(A|B)?

   • P(A and B) / P(B)
   • P(A and B) / P(A)
   • P(A) * P(B)
   • P(A or B) - P(B)

4. What is the sum of probabilities on the branches stemming from a single node in a tree diagram?

   • 0.5
   • P(A)
   • 2
   • 1

5. How do you calculate the combined probability along a single branch path in a tree diagram?

   • Add probabilities
   • Multiply probabilities
   • Divide probabilities
   • Subtract probabilities

6. When combining separate branch paths to find an 'or' probability on a tree diagram, what operation is used?

   • Subtract probabilities
   • Add probabilities
   • Multiply probabilities
   • Divide probabilities

7. If P(A and B) = 0.2 and P(B) = 0.4, what is P(A|B)?

   • 0.08
   • 2
   • 0.2
   • 0.5

8. What term describes events that cannot happen at the same time?

   • Conditional
   • Mutually exclusive
   • Independent
   • Exhaustive

9. If P(A) = 0.6, P(B) = 0.5, and P(A and B) = 0.3, are events A and B independent?

   • Cannot tell
   • No
   • Always
   • Yes

10. If P(A) = 0.4 and P(B|A) = 0.3, what is P(A and B)?

    • 0.12
    • 0.1
    • 0.75
    • 0.7

11. In a bag of 3 red and 2 blue counters, two are drawn without replacement. What is the probability both are red?

    • 3/5
    • 3/10
    • 9/25
    • 6/25

12. If events A and B are mutually exclusive with P(A)=0.3 and P(B)=0.4, what is P(A|B)?

    • 0.12
    • 1
    • 0
    • 0.7

13. What does a tree diagram primarily help visualise?

    • Discrete variance
    • Combined probabilities
    • Averages
    • Regression lines

14. If P(A'|B) = 0.2, what is P(A|B)?

    • 0.2
    • 0.5
    • 0.8
    • 1

15. When drawing items without replacement, what happens to the denominators on subsequent branches of a tree diagram?

    • Stay the same
    • Decrease by 1
    • Increase by 1
    • Double

16. What is true of two events A and B if P(A|B) equals P(A)?

    • Mutually exclusive
    • Independent
    • Conditional
    • Complementary

17. A test has a 90% accuracy for disease presence. If 5% of people have it, what type of diagram is best to calculate positive test probabilities?

    • Tree diagram
    • Box plot
    • Scatter diagram
    • Histogram

18. If P(A|B) = 1, what must be true about events A and B?

    • B is a subset of A
    • A and B are independent
    • P(A) = 0
    • A is a subset of B

19. What is the exact complement of getting at least one six in two dice rolls?

    • No sixes
    • Two sixes
    • At most one six
    • Exactly one six

20. If P(A) = 0.5 and P(B|A) = 0.4, what is the value of P(A and B)?

    • 0.8
    • 0.1
    • 0.9
    • 0.2

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