TEST VALIDITY

Content Validity

A test is said to have content validity if its content constitutes a representative sample of the language skills, structures, etc. with which it is meant to be concerned. The test would have content validity only if it included a proper sample of the relevant structures, and it depends upon the purpose of the test. In order to judge whether or not a test has content validity, we need a specification of the skills or structures, etc. that it is meant to cover. A comparison of test specification and test content is the basis for judgments as to content validity. Ideally these judgments should be made by people who are familiar with language teaching and testing but who are not directly concerned with the production of the test in question. The importance of content validity are the greater a test’s content validity, the more likely it is to be an accurate measure of what it is supposed to measure; and such a test is likely to have a harmful backwash effect. The content of tests should be determined by what is important to test, not what is easy to test.

Criterion-related Validity

There are essentially two kinds of criterion related validity: concurrent validity and predicative validity. The first is Concurrent validity, it is established when the test and the criterion are administered at about the same time. To exemplify this kind of validation in achievement testing, we should consider a situation where course objectives call for an oral component as part of the final achievement test. To establish the concurrent validity of the component, we should choose at random a sample of all the students taking the test. The second kind of criterion-related validity is predicative validity. This concerns the degree to which a test can predict candidates’ future performance.

Construct Validity

A test, part of a test, or a testing technique is said to have construct validity if it can be demonstrated that it measures just the ability which it is supposed to measure. The word ‘construct’ refers to any underlying ability (or trait) which is hypothesized in a theory of language ability. Construct validation is a research activity, the means by which theories are put to the test and are confirmed, modified, or abandoned. It is through construct validation that language testing can be put on a sounder, more scientific footing. But it will not all happen overnight; there is a long way to go. In the meantime, the practical language tester should try to keep abreast of what is known. When in doubt, where it is possible, direct testing of abilities is recommended.

Face Validity

A test is said to have face validity if it looks as if it measures what it is supposed to measure. Face validity is hardly a scientific concept, yet it is very important. A test which does not have face validity may not be accepted by candidates, teachers, education authorities or employers. It may simply not be used; and if it is used, the candidates’ reaction to it may mean that they do not perform on it in a way that truly reflects their ability.

The Use of Validity

In constructing tests, every effort should be made to ensure content validity. Where possible, the tests should be validated empirically against some criterion. Particularly where it is intended to use indirect testing, reference should be made to research literature to confirm that measurement of the relevant underlying constructs has been demonstrated using the testing techniques that are to be used.