Which among the following is different from the characteristics of a good test?

A good test is judged by certain psychometric characteristics -- properties of the test itself, describing how consistently and how truly it measures what it claims to measure. Reliability, validity, and objectivity are examples of such quality characteristics of a test.

Among the given options, three name qualities of the test itself, while one names a trait that a test can be designed to measure in the examinee. Aptitude is a person's inherent capacity or potential to learn or perform a specific skill -- it is a construct some tests measure, not a criterion by which the test's own quality is judged. This is why Aptitude is different from the other three.

• Reliability: how consistently a test yields the same results under similar conditions -- a quality characteristic of the test.

• Validity: the extent to which a test measures what it is designed to measure -- a quality characteristic of the test.

• Objectivity: freedom of scoring/interpretation from the individual examiner's personal bias -- a quality characteristic of the test.

• Aptitude: a trait/potential of the test-taker that a test may measure -- not a quality characteristic of the test itself.

Since Reliability, Validity, and Objectivity all describe the quality of the test, while Aptitude describes what a test measures in a person, Aptitude is the one that is different -- the correct answer.