OAS and effective duration binomial tree

CFA Level II Fixed Income
#1

While calculating the effective duration for a bond with effective duration, we find OAS and then add that OAS to the modified binomial tree( adjusted by +/- bps). Would we be adding OAS had it not been a credit risky bond?

#2

You would, but the OAS for a risk-free bond should be zero.

#3

got it! Thank you

#4

My pleasure.