assumptions regarding investor behavior are required by the capm
Capital asset pricing model
E ( R i ) − R f = β i ( E ( R m ) − R f ) ( \ displaystyle E ( R_ ( i ) ) - R_ ( f ) = \ beta _ ( i ) ( E ( R_ ( m ) ) - R_ ( f ) ) \ , )
E ( R i ) − R f = β i ( E ( R m ) − R f ) ( \ displaystyle E ( R_ ( i ) ) - R_ ( f ) = \ beta _ ( i ) ( E ( R_ ( m ) ) - R_ ( f ) ) \ , )