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IAI Actuarial Core Principles · Economic Modelling · Measures of investment risk

A fund's annual return is normally distributed with mean 9% and standard deviation 12%. What is the probability that the return is below 0%? (Use Φ(0.75)=0.7734.)

The shortfall probability is 22.66%. The standardised value is (0-9)/12 = -0.75, and Φ(-0.75) = 1 - 0.7734 = 0.2266. The 77.34% figure is the probability of a positive return, which is the opposite tail.

  1. A12.66%
  2. B22.66%Correct
  3. C27.34%
  4. D7.50%
  5. 77.34%

Explanation

z=(0-9)/12=-0.75. P(R<0)=Φ(-0.75)=1-0.7734=0.2266. The 77.34% option is the probability of exceeding zero, the wrong tail. The 27.34% option arises from wrongly using 1-0.7266.

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