The table uses the standard deviation of the portfolio's return as a measure of risk. A normal random variable, such as a portfolio's return, stays within two standard deviations of its average approximately $95\%$ of the time.

Suppose Lucia modifies her portfolio to contain $75\%$ diversified stocks and $25\%$ risk$-$free government bonds; that is$,$ she chooses combination D$.$ The average annual return for this type of portfolio is $15\mathrm{.}5\%,$ but given the standard deviation of $15\%,$ the returns will typically $($about $95\%$ of the time$)$ vary from a gain of $(-14\mathrm{.}5\%,4\mathrm{.}7\%,30\mathrm{.}5\%,45\mathrm{.}5\%)$ to a loss of $(-14\mathrm{.}5\%,0\mathrm{.}5\%,4\mathrm{.}7\%,45\mathrm{.}5\%).$