Final answer:
The standard deviation of the optimal portfolio can be calculated using the formula sqrt(wa^2 * sa^2 + wb^2 * sb^2), where wa and wb are the weights of the stocks and sa and sb are the standard deviations. The standard deviation of the given portfolio is 0.0941.
Step-by-step explanation:
The standard deviation of the optimal portfolio can be calculated using the formula:
Standard Deviation = sqrt(wa^2 * sa^2 + wb^2 * sb^2)
Where wa and wb are the weights of stocks a and b in the portfolio, and sa and sb are the standard deviations of stock a and b respectively.
Given the information provided:
wa = 0.7, sa = 1.3%, wb = 0.3, sb = 1.5%
Plug these values into the formula to calculate the standard deviation:
Standard Deviation = sqrt(0.7^2 * 1.3%^2 + 0.3^2 * 1.5%^2)
Standard Deviation = sqrt(0.49 * 0.0169 + 0.09 * 0.0225)
Standard Deviation = sqrt(0.008181 + 0.000675)
Standard Deviation = sqrt(0.008856)
Standard Deviation = 0.0941