May 08'23

Exercise

The probability of [math]x[/math] losses occurring in year 1 is [math]0.5x[/math] for [math]x=0,1, 2,\ldots[/math]. The probability of [math]y[/math] losses in year 2 given [math]x[/math] losses in year 1 is given by the table:

Number of losses in year 1 (x) Number of losses in year 2 (y) given x losses in year 1
0 1 2 3 4+
0 0.60 0.25 0.05 0.05 0.05
1 0.45 0.30 0.10 0.10 0.05
2 0.25 0.30 0.20 0.20 0.05
3 0.15 0.20 0.20 0.30 0.15
4+ 0.05 0.15 0.25 0.35 0.20


Calculate the probability of exactly 2 losses in 2 years.

  • 0.025
  • 0.031
  • 0.075
  • 0.100
  • 0.131

Copyright 2023. The Society of Actuaries, Schaumburg, Illinois. Reproduced with permission.

May 08'23

Solution: E

[[math]] \begin{align*} P( x= 1, y= 1)= P( y= 1| x= 1) P( x= 1)= 0.3(0.5)^2= 0.0753 \\ P(x= 2, y= 0)= P(y= 0| x= 2) P(x= 2)= 0.25(0.5)^3=0.03125 \\ P(x=0,y=2) = P(y=2 | x = 0 ) P(x=0) = 0.05(0.5)^1 = 0.025 \end{align*} [[/math]]

The total is 0.13125.

Copyright 2023. The Society of Actuaries, Schaumburg, Illinois. Reproduced with permission.

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