Standard deviation rate of return is a measure of risk in the stock market. an investment manager claims that the standard deviation rate of return for his portfolio is less than the general market, which is known to be 18%. treating the past 10 years as a random sample, you find the standard deviation rate of return of the manager’s portfolio is 16%. does this represent sufficient evidence to conclude that the investment manager’s portfolio has less risk than the general market? use a = 0.05.