The alpha factor measures a stock's own volatility; this Greek letter compares it to the entire market
Beta is a measure of the risk arising from exposure to general 
market ... A beta below 1 can indicate either an investment with lower volatility 
than the ... to a benchmark for the fund, rather than from exposure to the entire 
market... [DOC] [TLE] Investment Performance Measurement: Return, Risk, Alpha & Beta [PAR] 2 Investment Performance Measurement: Return, Volatility, Alpha & Beta ...