Final answer:
The Wechsler Adult Intelligence Scale is the most commonly used adult IQ test in the U.S. A score of 70 or below might indicate an intellectual disability, and age is crucial for selecting the appropriate intelligence test.
Step-by-step explanation:
1. In the United States, the most commonly used adult IQ test is called the Wechsler Adult Intelligence Scale.
2. If an individual scores 70 or below on an IQ test, the test may yield a diagnosis of intellectual disability (ID). A score of about 70 on a test with a mean of 100, combined with major deficits in adaptive functioning and the onset of these deficits before age 18, indicates ID according to criteria from the Diagnostic and Statistical Manual of Psychological Disorders (APA, 2013).
3. Before choosing which intelligence test to administer, a psychologist needs to know the client's age.