Tests are standardized procedures used to measure and predict behavior. Psychological tests specifically measure personality traits objectively through verbal and non-verbal responses. There are two main types: individual tests administered to one person at a time, and group tests administered simultaneously to multiple people. Ability tests measure accuracy and speed, while personality tests gauge typical behaviors like traits and temperament. Personality tests are used for assessing theories, diagnosing problems, evaluating therapy effectiveness, and predicting future behavior.