The effective interest rate is given by
[tex]r= \left(1+\frac{i}{t}\right)^t-1 [/tex]
Given that the bond yeilds an annual yield of 6.7 percent and pays coupons twice a year.
The effective interest rate is given by:
[tex]r= \left(1+\frac{0.067}{2}\right)^2-1 \\ \\ =(1+0.0335)^2-1 \\ \\ =(1.0335)^2-1=1.0681-1 \\ \\ =0.0681=6.81\%[/tex]