Langtest

VALIDITY AND RELIABILITY

Validity refers to the appropriatenss of the interpretations of test results..... Reliability refers to the consistency of test results.... Both are important concepts in the development and use of achievement tests..... Validity is most important ..... but reliability provides the consistency that makes validity possible, and indicates the confidence to be placed in test interpretations.
The two most important qualities to consider in the preparation and use of achievement tests are validity and reliability. Both are essential to effective testing and should be understood by anyone working with tests even though it is frequently unnecessary to make elaborate validation and reliability studies of informal achievement tests, a clear grasp of these concepts will contribute to skill in test construction and test interpretation.
METHODS OF DETERMINING VALIDITY
In a very general sense, validity is concerned with the extent to which tests results serve their intended use. Questions of validity in the first instance are concerned with what behavioral responses are being measured by the test, and the second instance with how closely the scores on the test are related to some other valued performance. Thus, “questions of validity are questions of what may properly be inferred from a test score”(American Psychological Association 1974). Specifically, validity refers to the appropriateness of the interpretations of test results(typically with regard to some practical use of the test result).
The concept of validity, as used in testing, can be clarified further by nothing the following general point:
1. Validity refers to the interpretation of test results(not to the test it self).
2. Validity is inferred from available evidence(not measured).
3. Validity is specific to a particular use (selection, placement, evaluation, of learning, and so forth).
4. Validity is expressed by degree(for example, high, moderate, or low).

Basic types of validity

Type Question to be answered
Content validity

Criterion-related validities


Construct validity How adequately does the test content sample the larger domain of situations it represent?
How well does test performance predict future performance (predictive validity) or estimate present standing (concurrent validity) on some other valued measure called a criterion?
How well can test performance be explained in terms of psychological attributes.



Content Validity
It should be clear from this discussion that the key element in content validity is the adequency of the sampling.Content validity is a matter of determining whether the sample is representative of the larger domain it is supposed to represent. Content validity is especially important in achievement testing. We can build a test that has high content validity by (1)identifying the subject-matter topic and the learning outcomes to be measured, (2)preparing a set of specifications, which defines the sample of items to be used, (3)constructing a test that closely fits the set of specifications.
Content validity is of major concern in achievement testing, and it is important to have in both criterion- referenced and norm-referenced tests.
Criterion –Related Validities
There are two types of criterion-related validity. The first is concerned with the use of test performance to predict future performance on some other valued measure called a criterion. For example, we might use scholastic aptitude test scores to predict course grades(the criterion). The second type of criterion-related validity is concerned with the use of test performance to estimate current performance on some criterion.
The key element in both types of criterion-related validity is the degree of relationship between the two sets of measures: (1)the test scores, (2) the criterion to be predicted or estimated.