You don't say whether you are carrying this survey out for interest or in order to assess a safety hazard.
Might I suggest that if your interest is safety, minor loadsheet errors which cannot affect the safety of the aircraft and cannot affect security adversely, may be reasonably discounted?
For example, bags calculated at 13Kgs on a domestic flight (when the figure should be 11Kgs) will have no impact. Showing all the bags in the forward hold when they were loaded in the rear, may, depending upon the aircraft type (in an ATR-72 you would be in danger of running out of trim).
Correct total numbers of passengers must be important, as this is a security issue, though you must then assess probability of an error occurring on the flight which is subject to a terrorist threat - this will be low, though these days we must dot all our 'i's and cross our 't's.
You may employ a risk matrix (probability versus severity) in order to get a handle on these issues.
If you're doing your survey in the interest os safety, good luck. I hope you're not doing it so that management can call people who have erred into the office for a chat without coffee. If this latter is the case, ask your managers who it was who recruited, trained, and tested these pilots, and who it was who placed them in positions of responsibility...?