Not enough information old chap.
First, are you looking for quantified error (normal or skewed normal distribution) or simple right/wrong (either binomial or more hopefully Poisson distribution).
In reading across, are the levels of pilot qualification and experience the same? Are the load sheets of comparable complexity?
There are standard methods for working out the tolerance of accuracy on your result based upon sample size. I personally haven't done that sort of analysis for 10 years, so honestly can't remember how you do it, but my gut feeling is that if you're looking at a normal distribution, and say 100 pilots x 10 load sheets each, the confidence will be pretty high ON THAT POPULATION. Proving whether you can read across to another population is another thing.
My personal experience is that most days, about 30% of pilots are capable of ******ing up a load sheet, this is one of many reasons why airlines employ dispatchers.
G