In the fifth edition of The Handbook of Fixed Income Securities (Irwin Profes- sional Publishing, 1997), page 104 gives the following formula for the approximate convexity measure: P. + P-2(P) 2(P)(Dy)

where the variables are defined as in equation (4.24) of this chapter. Compare this formula with the approximate convexity measure given by equation (4.24). Which formula is correct?

AppendixLO1