Final answer:
It is confirmed that you have located the psoas major muscle when you observe hip flexion. The psoas major is part of the iliopsoas group, and this action is distinct from the role of the pronator teres, which is involved in forearm pronation.
Step-by-step explanation:
You know it is confirmed you found the psoas major muscle when you observe the movement of hip flexion. The psoas major, along with the iliacus, forms the iliopsoas group which is primarily responsible for flexing the thigh at the hip joint. In contrast, the pronator teres is a muscle that helps to pronate the forearm; it originates on the humerus and inserts on the radius, and is not associated with confirming the location of the psoas major.