What are the Difference between Aptitude and Achievement Tests?

	Aptitude	Achievement
Definition	An aptitude test measures what knowledge an individual has already acquired prior to taking the test.	Achievement tests are general assessments given to individuals in order to measure their comprehension of acquired skills and content.
Uses	Aptitude tests measure academic knowledge in subjects such as math, English language and literature, science and reading comprehension.	These tests are used to place students in appropriate level courses, various types of employment etc.
Test Formats	Major aptitude tests have a specific structure and format that is followed for all tests.	Achievement tests can be developed by teachers and given in classrooms, so there are no formal guidelines.
Types	Aptitude tests, such as the Praxis, ACT and SAT, are often administered outside of the classroom.	Achievement assessments are most often administered in the classroom. Quizzes, final exams, practice SATs etc.
Scoring	Aptitude tests are scored by professional test-scorers.	Achievement tests can be scored by the teacher in the classroom setting.