The Characteristic of a Good Test

Wiersma divided content validity onto two parts, content validity of teacher-constructed tests and content validity of published tests. 23 Content validity of teacher-constructed test essentially depends on the sampling of items. If the test items adequately represent the domain of possible items, the test has adequate content validity. When a test is not content valid, there are two consequences. First, the students cannot demonstrate skills that they possess if they are not tested. Second, irrelevant items are presented that the students will likely answer incorrectly only because the content was not taught. Both of these consequences tend to lower the test scores; as a result, the test score is not an adequate measure of student performance relative to the content covered by instruction. Most teachers are quite familiar with the content they cover during instruction, and, to a large extent, teacher-constructed tests have an inherent content validity. However, in planning a test, teachers can use a straightforward procedure that tends to improve content validity. The second part is content validity of published tests. Teachers may, at least on occasion, use published tests, some of which accompany curriculum materials. The tests constructed for a specified textbook or set of materials usually have high content validity if the materials are used as intended for instruction. Sometimes materials are used as supplementary and are only partially covered, in which case any accompanying tests would at least need to be reviewed for content validity. Many school system use standardized achievement tests prepared by commercial publisher; for the most part, these are norm-referenced tests. The content of such tests is fixed and is designed to have broad coverage. Therefore, although such tests are usually very well constructed technically, they may lack adequate content validity when used in a specific situation. When curriculum committees or test selection committees in a school system 23 Ibid., p.p. 185-186 are attempting to select a standardized achievement test, they are usually grappling with the problem of content validity. 24 Other statement comes from Groundlund “Content validity is a matter of determining whether the sample is representative of the larger domain it is supposed to represent ”. 25 In other words, content validity is concerned with what goes into the test. Thus, the degree of content validity in a classroom test relates to how well the test measure the subject matter content studied and the behaviors which the test tasks require. A test will have high content validity if the items are representative of the population of possible task. The focus of content validity then is on the adequacy of the sample and not simply on the appearance of the test. The test is examined to determine the subject-matter content covered and responses pupil are intended to make to the content, and this is compared with the domain of achievement to be measure. Thus, content validity may be defined as the extent to which a test measures a representative sample of the subject-matter content and the behavioral changes under consideration. 26 There are two importance of content validity. First, the greater test‟s content validity, the more likely it is to be an accurate measure of what it is supposed to measure. Secondly, such a test is likely to have a harmful backwash effect. Areas which are not tested are likely become areas ignored in teaching and learning. The best a safeguard against this is to construct full test specification and to ensure that the test content is a fair reflection of these. 27 24 Ibid., p.187 25 N.E. Groundlund, Constructing Achievement Test, London : Prentice-Hall of International, inc., 1982 p. 127 26 Wilmar tinambunan, Evaluation of Student Achievement, p. 12 27 Athur Hughes, Testing for Language Teacher, p.p. 22-23 2. Face Validity Face validity is a surface or appearance of test. As Alderson said “Face