Types of tests can be categorized as individual tests, group tests, verbal tests, non-verbal tests, informal tests, standardized tests, intelligence tests, aptitude tests, achievement tests, attitude tests and personality tests. Tests are used to measure students' skills, knowledge and abilities in order to help teachers provide effective instruction and help students improve. There are two main categories of tests - informal teacher-made tests and formal standardized tests developed by experts. Personality tests evaluate thoughts, emotions, attitudes and behaviors to assess personality traits.