Training/development, and social science in general is validity

One of, if not the most important topic in training/development, and social science in general is validity. Validity is the idea for example, that the training system you are implementing actually predicts better performance. So if a system is valid, as an employee's score increases on a training measure, their performance score should be positively correlated with that score. The assignment this week is to watch the video below, and simply list out potential threats to the validity of this performance appraisal system. For example, the same questions are not asked of each employee, so it is difficult to compare answers (problem) with scores (there's not scores, another problem) to performance ratings. Try to come up with a minimum of 6 potential problems with this performance appraisal system. 

 https://www.youtube.com/watch?v=gYgveD5B-V0