Question: According to Investment Digest ("Diversification & the Risk/Reward Relationship", Winter 1994, 1-3), the mean of the annual return for common stocks from 1926 to 1992 was 15.4 percent, & the standard deviation of the annual return was 21.5 percent. During the same 67-year time span, the mean of the annual return for long-term government bonds was 5.5 percent, & the standard deviation was 7.0 percent. The article claims that the distributions of annual returns for both common stocks & long-term government bonds are bell-shaped & approximately symmetric. Assume that these distributions are distributed as normal random variables with the means & standard deviations given previously.
[A] Calculate the probability that the return for common stocks will be less than 20 percent.
[B] Calculate the probability that the return for common stocks will be greater than 0 percent.