Final answer:
Portfolio A has the highest expected return, making it the preferred choice despite the same level of risk as Portfolio B.
Step-by-step explanation:
When comparing two investments, a rational investor would examine both the expected return (r) and the volatility or risk (indicated by the standard deviation σ).
Given the choice between Portfolio A with an expected return (r) of 19% and a standard deviation (σ) of 21%, and Portfolio B with an expected return (r) of 15% and the same standard deviation (σ) of 21%, a rational investor would generally prefer the investment with the higher expected return if the risk level is the same.
Therefore, the preference would be:
- Portfolio A - Because it has a higher expected return of 19% compared to Portfolio B's 15%, while both portfolios have the same level of risk (σ = 21%).
In terms of safety, neither investment can be considered safer than the other since they both share the same level of risk (standard deviation).
However, in terms of return, Portfolio A is the preferred choice for having the highest expected return, which on average compensates for the identical level of risk between the two investments.