It's more like: you have a machine that evaluates whether the peanut butter you're producing is up to spec (right viscosity, right fat content, whatever), and i

It's more like: you have a machine that evaluates whether the peanut butter you're producing is up to spec (right viscosity, right fat content, whatever), and if your machine complains and says your peanut butter isn't coming out right, you need a way to know if the problem is actually with your peanut butter or if it's that your peanut butter testing machine is miscalibrated. If you put the known-acceptable reference peanut butter through it and your machine says that's fine, it's your peanut butter, but if that also produces an error, you know it's your machine.