Gamma Distribution and Moment Generating Functions
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Questions and Answers

What are the parameters of the gamma variable that models the claim amount X?

  • α=3, λ=1/4 (correct)
  • α=2, λ=1/2
  • α=1, λ=1/5
  • α=4, λ=1/3
  • Which moment generating function corresponds to a gamma variable with parameters α=3 and λ=1/4?

  • M(t) = (1 - 4t)^{-2}
  • M(t) = (1 - rac{4t}{3})^{-3} (correct)
  • M(t) = (1 - t)^{-3/4}
  • M(t) = (1 - 4t)^{-3}
  • What is the expression derived from using moment generating functions in the problem?

  • $rac{1}{2}X + X^2$
  • $rac{1}{4}X^2 - X^2$ (correct)
  • $rac{1}{2}X^2 + X^2$
  • $rac{1}{4}X^2 + X^2$
  • To find the probability that a claim amount exceeds £20,000, what must you determine about the gamma distribution?

    <p>The cumulative distribution function</p> Signup and view all the answers

    If £20,000 corresponds to a certain z-score, what is the z-score formula for gamma distributed variables?

    <p>$z = rac{X - ext{mean}}{ ext{std dev}}$</p> Signup and view all the answers

    Study Notes

    Gamma Distribution Parameters

    • Claim amount X is modeled using a gamma distribution with shape parameter α=3 and rate parameter λ=1/4.
    • The probability density function for a gamma variable is defined, which involves the parameters α and λ.

    Moment Generating Functions

    • Moment generating functions (MGFs) are used to calculate moments of the distribution.
    • For a gamma distribution, the MGF is given by the formula: M(t) = (1 - λt)^{-α}, valid for t < 1/λ.
    • The second moment (E[X^2]) can be calculated using the second derivative of the MGF evaluated at t=0.

    Claim Amount Calculation

    • To show that ( \frac{1}{4}X^2 - X^2 ), differentiate the MGF and calculate expected values accordingly.
    • Utilize properties of MGFs to derive relationships between moments.

    Probability Calculation

    • To find the probability that a claim amount exceeds £20,000, convert this value to units of the gamma variable (in thousands of pounds).
    • Calculate the threshold: for X exceeding £20, use the relationship (X > 20) in terms of the gamma distribution.
    • Access and utilize gamma distribution tables to find cumulative probabilities for the calculated values.

    Conclusion

    • The use of the gamma distribution is essential in modeling claim amounts for industrial policies.
    • Applying moment generating functions provides insight into the variability and expected outcomes of claims.

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    Description

    Quiz on gamma distribution parameters and moment generating functions. Learn about the probability density function, calculating moments, and formulae for MGF.

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