Lesson 3B.3.2-3B.3.3

3B.3.2-3B.3.3 Mean and variance of geometric and negative binomial distributions Quiz: Pearson Edexcel Further Maths, Unit 12

20 questions

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Lesson 3B.3.2-3B.3.3, Mean and variance of geometric and negative binomial distributions: 20 multiple choice questions for the Pearson Edexcel Further Maths (9FM0), Unit 12: Geometric and negative binomial distributions, written with Revision Ninja.

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The 20 questions

  1. For a geometric distribution with parameter p, what is E(X)?

    • 1/p^2
    • (1 - p)/p
    • 1/p
    • p
  2. For a geometric distribution with parameter p, what is Var(X)?

    • p(1 - p)
    • (1 - p)/p^2
    • 1/p^2
    • (1 - p)/p
  3. For a negative binomial distribution with parameters r and p, what is E(X)?

    • rp
    • r/p
    • r(1 - p)/p
    • r/(1 - p)
  4. For a negative binomial distribution with parameters r and p, what is Var(X)?

    • rp^2/(1 - p)
    • r(1 - p)/p^2
    • r/p^2
    • r(1 - p)/p
  5. A geometric distribution has p = 0.2. What are its mean and variance?

    • Mean 5, variance 20
    • Mean 0.2, variance 5
    • Mean 5, variance 5
    • Mean 4, variance 16
  6. A negative binomial distribution has r = 3 and p = 0.5. What is its mean?

    • 3
    • 12
    • 6
    • 1.5
  7. A geometric distribution has p = 0.25. What is its variance?

    • 3
    • 4
    • 12
    • 1.5
  8. A negative binomial distribution has r = 4 and p = 0.8. What is its variance?

    • 4
    • 0.8
    • 1.25
    • 5
  9. How many rolls of a fair die are expected to be needed to get a six?

    • 36
    • 6
    • 3.5
    • 1/6
  10. A geometric distribution has mean 4. What is p?

    • 0.75
    • 0.4
    • 0.25
    • 4
  11. A geometric distribution has mean 5 and variance 20. What is p?

    • 0.2
    • 0.5
    • 0.8
    • 0.1
  12. Each attempt succeeds with probability 0.1. What is the expected number of attempts needed to get 2 successes?

    • 10
    • 2
    • 20
    • 5
  13. Each attempt succeeds with probability 0.1. What is the variance of the number of attempts needed to get 2 successes?

    • 180
    • 90
    • 20
    • 18
  14. A geometric distribution has mean 8. What is P(X = 1)?

    • 0.125
    • 0.8
    • 0.875
    • 8
  15. For a geometric distribution with mean m, which expression gives the variance in terms of m and p?

    • m^2 (1 - p)
    • m (1 - p)
    • m^2 / p
    • m (1 - p)/p
  16. A negative binomial distribution has mean 12 and variance 24. What is r?

    • 2
    • 6
    • 3
    • 4
  17. For a geometric distribution with p = 0.3, what is E(X^2)?

    • 17/9
    • 170/9
    • 10/3
    • 100/9
  18. A negative binomial distribution has r = 2 and p = 0.25. What is its standard deviation to 2 decimal places?

    • 2.45
    • 8.00
    • 4.90
    • 24.00
  19. A fair coin is tossed until two tails appear. What is the expected number of tosses?

    • 4
    • 2
    • 3
    • 1
  20. Which negative binomial mean formula reduces to the geometric mean when r = 1?

    • r/p gives 1/p
    • r(1 - p)/p gives (1 - p)/p
    • rp gives p
    • r/(1 - p) gives 1/(1 - p)

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