Portfolio risk is the variability of returns, which refers to how much the return on an investment fluctuates over time. In finance, a risk-averse investor is someone who prefers investments with lower returns and lower risk over investments with higher returns but higher risk. Assuming a risk-averse investor who owns stock in Company A wants to add either the stock of B or C to her portfolio, with the expectation that all three stocks offer the same expected return and total variability, she should consider the correlation of return between the stocks A, B, and C.
The correlation of return between stocks A and B is -0.15 and between A and C is +0.15. Since the investor is risk-averse, she will want to choose the stock that will help her to diversify and reduce the overall risk of her portfolio. This means that she will want to choose the stock that has the lowest correlation with the stock she already owns, which in this case would be either B or C.
Since the correlation between A and B is negative (-0.15), this means that the returns on the two stocks move in opposite directions. This can be a good thing for the investor because when one stock is doing poorly, the other stock may be doing well, which can help to reduce the overall risk of the portfolio. On the other hand, since the correlation between A and C is positive (+0.15), this means that the returns on the two stocks move in the same direction. This can be a bad thing for the investor because when one stock is doing poorly, the other stock may also be doing poorly, which can increase the overall risk of the portfolio.
Therefore, the investor should add stock B to her portfolio, which would help to diversify her portfolio and reduce overall risk, while still maintaining the same expected return and total variability.