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

 There are four important characteristics of a good test. 1. Reliability 2. Validity 3. Objectivity 4. Usability. Reliability can be defined as the degree of consistency between two measurements of the same thing. Theoretically, reliability is defined as the ratio of the true score and observed score variance. Objectivity is an important characteristic of a good test. It affects both validity and reliability of test scores. Objectivity of a test refers to the degree to which equally competent scores obtain the same results. So a test is considered objective when it makes for the elimination of the scorer's personal opinion and bias judgement. Validity means truth- fullness of a test. It means to what extent the test measures that, what the test maker intends to measure. Aptitude is not a measure of good test.