Do bonds reduce the overall risk of an investment portfolio? Let x be a random variable representing annual percent return for the Vanguard Total Stock Index (all Stocks). Let y be a random variable representing annual return for the Vanguard Balanced Index (60% stock and 40% bond). For the past several years, assume the following data. Compute mc022-1.jpg. x: 11 0 36 25 31 27 28 -11 -11 -25 y: 9 -4 26 14 26 17 14 -4 -5 -9