(a) Computex,x²,y,y².

x	x2
y	y2

Do bonds reduce the overall risk of an investment portfolio? Letxbe a random variable representing annual percent return for Vanguard Total Stock Index (all stocks). Letybe a random variable representing annual return for Vanguard Balanced Index (60% stock and 40% bond). For the past several years, we have the following data.

x:	37	0	31	15	22	18	31	11	20	18
y:	28	8	28	23	22	25	11	8	3	2