Validity tells us whether the test is measuring what it purports to measure. For example, an algebra test is supposed to measure student competency in algebra. But if it includes word problems, such a test may be a challenge for students with poor English language skills. It would, in effect, be measuring not simply algebra skills but English language skills as well. Thus, the test would measure both algebra and English skills for one subgroup of students, algebra alone for the rest of the students for whom language is not an issue. This is different from the stated goal of being an algebra test for all students.
Validity refers to the extent to which an assessment task measures the knowledge and ability it is supposed to measure.
They are valid when they have the following attributes:
They are a reflection of knowledge and skill which is related to instruction and not test-taking ability, memorization, study guides, etc. They engage and motivate students to perform to the best of their abilities and they are consistent.
When test scores are used to make inferences about student achievement, it is important that the assessment supports those inferences. In other words, the assessment should measure what it was intended to measure in order for any uses and interpretations about test results to be valid. The results of an assessment should be able to predict a student’s further success in the areas being measured.