Achievement tests measure what in comparison to aptitude tests?

Achievement tests are designed to assess an individual's acquired knowledge or proficiency in specific subjects, such as mathematics, reading, or science. These tests focus on what a person has learned and the skills they currently possess based on their past experiences and education.

In contrast, aptitude tests are intended to evaluate an individual's potential to succeed in future learning or performance tasks. They measure ability and the likelihood of success in certain areas, rather than knowledge already gained.

The correct answer highlights this distinction clearly—achievement tests assess what a person has already learned and demonstrated, while aptitude tests focus on predicting future performance based on innate abilities or potential. This understanding is crucial, as it delineates the fundamental differences in purpose and application between the two types of tests.