Purpose: The purpose of this article is to describe the indicators of diagnostic validity and to demonstrate the informative value of the pretest probability of two tests, the supraspinatus test and magnetic resonance imaging (MRI), on diagnosis and management by using three case scenarios of rotator cuff pathology as examples. Summary of Key Points: Patients' attributes and validity indices of clinical tests are important to consider in reaching an optimal diagnosis. We compared the impact of the supraspinatus (Jobe) test with MRI of the shoulder in three fictional cases with different severity of rotator cuff pathology. The methodological approach of clinical decision-making at the patient level is discussed. Conclusion and Recommendations: Clinicians are required to make decisions based on incomplete data and imperfect clinical tests with falsenegative and false-positive results. Estimating the pretest probability of pathology is often an educated guess. However, without an explicit estimate of the pretest probability of suspected pathology, a test result has no clearly defined informative value. The Bayesian approach provides a logically correct way to arrive at a specific post-test probability.