Variance of a two-regime return

A trading day is "calm" with probability 0.70.7 and "volatile" with probability 0.30.3. On a calm day the return is Normal with mean 00 and standard deviation 1%1\%; on a volatile day it is Normal with mean 00 and standard deviation 3%3\%. What is the variance of a single day's return (in %2\%^2)? Give a decimal to two places.

Show hints (2)+
  1. Condition on the regime - law of total variance.
  2. The means match, so only the average within-regime variance survives.

Answer

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3.4 (± 0.01)

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