In an article published in the Psychological Bulletin, Frank Schmidt and John Hunter analyzed 85 years of research in order to underline the most effective methods for recruitment (entry and mid-senior levels). They arrived at the conclusion that Cognitive Ability Tests were the most sufficient predictor of on-job success and performance. Simply put, a person with a higher score in a Cognitive Ability Test is likely to perform better than a peer who has scored lesser. The predictive validities of different types of selection tools are presented below and you can perceive a clear winner.
Creating a cognitive skills assessment for prospective employees is not an easy task. Neither it is a test that can be put together using a few generalized questions you find on the internet.