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Hey @BobBarkerPlaysPlinko‌, you may have got it the other way round. Modified duration is only suitable for option-free bond as Modified Duration assumes that changes in yield of a bond does not affect its cash flow. That is not true for a bond with embedded options, e.g. callable bond.
Effective duration on the other hand is the change in bond Price due to a 1% Change in interest rates, that also takes into account the impact of changing interest rates to the bond’s cash flow (and hence price).
In other words, for a striaghforward bond without embedded options, modified duration should be equal to effective duration.
Hope this helps