Picture a doctor trying to diagnose whether a patient is seriously ill. The doctor cannot run every possible test on every patient — that would take too long, cost too much, and be unnecessary. Instead, she looks at the patient’s symptoms, age, and medical history to figure out where problems are most likely to hide, then orders the right tests. Auditors face exactly the same puzzle. They cannot check every single transaction a company makes, so they need a logical way to decide where to focus their work. That is what the audit risk model does: it is a thinking tool that helps auditors plan an audit that is both effective and efficient.