A new way of validity test was proposed to test the prescriptions for effective supervision as specified in Situational Leadership Theory (Hersey & Blanchard, 1977). The theory has received little empirical support and has been criticized on theoretical grounds. Moreover, past validity tests of the theory may be biased in terms of methodological processes. To address the issue, an omnibus test by using the cosign curve was proposed. Applying the test to data from 1195 salespeople across 374 stores working for a large Japanese apparel company showed no support for the theory. With the help of the test, the author additionally explored the modified assumptions of the theory that follower maturity moderates the relationship of leader task and relationship behaviors with indicants of follower performance.
