The two concepts may sound the same but actually differ in many ways. Testing intelligence measures a person's ability to reason, solve some particular problems, and even think abstractly, rather than recalling learned information.

On the other hand, testing for knowledge evaluates how much information or skills a person has acquired through education or experience. In terms of use, intelligence tests are appropriate when assessing cognitive potential or learning ability, while knowledge tests are more suitable for measuring academic achievement or job-related expertise.

However, using the first one alone can be not so good in educational settings where prior learning and cultural background greatly influence performance. With this, knowledge tests may be unfair when used to judge a person's overall ability to learn or adapt.