What can validity testing reasonably tell you and what can it not tell you?

So when people come into our office, we always ask them to give their best effort.

And we tell them that, you know, if they're having a problem to please let us know.

If we see them doing something that's not safe, we're going to let them know.

But when we do validity testing, what we're trying to look at is the correlation between someone's participation and abilities to perform activities versus their storyline.

So what I'm trying to determine, is there a correlation? And when I collect all my data that we're doing in a functional capacity evaluation, if somebody's given their best effort, I can say, yes, with certainty that this is what a person can do or not do in a work-related or home environment.

But if somebody doesn't give their best effort, it makes it really a challenge.

What can a home assessment do? reveal about the true impact of an injury? And how can small modifications help someone regain independence?