If the observed price of an option is assumed to be the fair price and the option pricing model is assumed to be the model that would generate the fair price, then the implied volatility is the yield volatility that, as an input to the option pricing model, would produce the observed option price.

If the observed price of an option is assumed to be the fair price and the option pricing model is assumed to be the model that would generate the fair price, then the implied volatility is the yield volatility that, as an input to the option pricing model would produce the observed option price.

To forecast yield volatility, an analyst should compute a recent standard deviation of yield changes. It is acceptable to assume the mean yield change is zero and use the average of recent squared rate changes. This can be a simple average or a weighted average where the more recent squared changes are weighted more heavily.