Hehe , in simpler terms yes. More specifically how often does a mutation occur that provides a specific advantage to the 'phenotype'.
(Phenotype is the word for the physical expression of the genes, that is to say, the physical form of the individual.)
Well, that's almost impossible to determine. Consider an individual born with a mutation that isn't fatal or detrimental. You're looking at it right after it was born. Let's say you even know exactly what the mutation does, because it's caused some observable physical effect. How do you determine whether or not it's a beneficial mutation? There's no way to know if the mutation is useful or not until the individual reproduces, because "beneficial" has to be taken in relation to the environment the individual inhabits and is determined by whether or not the individuals with the mutation tend to leave more survivng offspring.
It's not like we have a meter that we can point at a mutation and see if it's beneficial or not. Sometimes mutations can be both harmful
and beneficial, like sickle cell anemia in humans. It all depends on environment.