Alpha and beta

Beta is a measure of systematic (market) risk. The broad market is assigned a beta of 1.0. A security with a beta of 1.5 has historically moved 50% more than the market in both directions, while a beta of 0.6 indicates a security that moves only 60% as much. A negative beta means the security tends to move opposite the market. Beta says nothing about how good an investment is — only how volatile it is relative to the market.

Alpha is the excess return an investment delivered beyond what its beta would predict. Conceptually, alpha = actual return − expected return, where the expected return is the risk-free rate plus beta times the market's excess return over that risk-free rate. If a fund with a beta of 1.2 was expected to return 10% and actually returned 13%, its alpha is +3%. A positive alpha suggests the manager added value; a negative alpha suggests the return did not justify the risk taken.

Together the two numbers separate two different questions. Beta answers "how much market risk am I taking?" and alpha answers "was I paid for it?" Beta is also the basis of portfolio construction — a portfolio's beta is the weighted average of its holdings' betas, so an investor can dial market exposure up or down deliberately. Because alpha is measured against a beta-adjusted benchmark, comparing an aggressive fund to a conservative one on raw return alone is misleading.

Exam questions typically test the interpretation rather than the arithmetic: identifying whether a high-beta stock is appropriate for a risk-averse client, or recognizing that positive alpha indicates risk-adjusted outperformance. The SIE and Series 6 cover alpha and beta within investment company material, and the Series 65 treats them alongside standard deviation, correlation, and other descriptive statistics used in portfolio analysis.