Here are the returns on two stocks.

Digital Cheese Executive Fruit

January $+16+9$

February $4+1$

March $+6+7$

April $+8+16$

May $5+2$

June $+4+7$

July $34$

August $93$

Required:

a$-1.$ Calculate the variance and standard deviation of each stock.

a$-2.$ Which stock is riskier if held on its own?

b$.$ Now calculate the returns in each month of a portfolio that invests an equal amount each month in the two stocks.

c$.$ Is the variance more or less than halfway between the variance of the two individual stocks?