Answer:
content validity
Explanation:
Based on the scenario being described within the question it can be said that the best type of validation to be used would be content validity. This term refers to the extents as to which a test measures exactly what it was intended to measure. This would be the best validation for this test as the firm would need to know all of the aspects of the types of errors that the individuals has found, which is what the test was designed to do.