Describe the difference between achievement and aptitude tests and summarize what we know about the extent to which they measure what they purport to measure.

Achievement test or content test is designed to measure how much an individual has learned the skill or knowledge provided in a course, so achievement test aims to identify weaknesses and strength of an individual with respect to a specific taught course or textbook.

Aptitude test is a test designed to measure an individual's specific skill, aptitude, or potential. It does not follow a certain course or textbook and does not need any preparation, unlike achievement test.

Achievement test makes decision about how much progress a person had in the past, while aptitude test makes decision or prediction on future by finding a person's potentials.