Achieving Beneficial Backwash

TEST THE ABILITIES WHOSE DEVELOPMENT YOU WANT TO ENCOURAGE

For example, if you want to encourage oral ability, then test oral ability. This is very obvious, a straightforward matter of content validity, yet it is surprising how often it is not done. There is a tendency to test what it is easiest to test rather than what it is most important to test. Reasons advanced for not testing particular abilities may take many forms. It is often said, for instance, that sufficiently high reliability cannot be obtained when a form of testing (such as an oral interview) requires subjective scoring.

SAMPLE WIDELY AND UNPREDICTABLY

Normally a test can measure only a sample of everything included in the specifications. It is important that the sample taken should represent as far as possible the full scope of what is specified. If not, if the sample is taken from a restricted area of that specifications, then the backwash effect will tend to be felt only in that area. The new TOEFL writing test will set only two kinds of tasks: compare/ contrast; describe/interpret chart or graph. The likely outcome is that much preparation for the test will be limited to those two types of task. The backwash effect may not be as beneficial as it might have been had a wider range of tasks been used.

USE DIRECT TESTING

Direct testing implies the testing of performance skills, with texts and tasks as authentic as possible. If we test directly the skills that we are interested in fostering, then practice for the test represents practice in those skills. If we want people to learn to write compositions, we should get them to write compositions in the test. If a course objective is that students should be able to read scientific articles, then we should get them to do that in the test. Immediately we begin to test indirectly, we are removing an incentive for students to practice in the way that we want them to.

BASE ACHIEVEMENT TEST ON OBJECTIVES

If achievement tests are based on objectives, rather than on detailed teaching and textbook content, they will provide a truer picture of what has actually been achieved. Teaching and learning will tend to be evaluated against those objectives. As a result, there will be constant pressure to achieve them.

ENSURE TEST IS KNOWN AND UNDERSTOOD BY STUDENTS AND TEACHERS.

However good the potential backwash effect of a test may be, the effect will not be fully realized if students and those responsible for teaching do not know and understand what the test demands of them, the rationale for the test, its specifications and sample item should be made available to everyone concerned with preparation for the test. This is particularly important when a new test is being introduced, especially if it incorporates novel testing methods. Another, equally important, reason for supplying information of this kind is to increase test reliability.

COUNTING THE COST

One of the qualities of tests which trips quite readily off the tongue of many testers, after validity and reliability, is that of practicality. Other things being equal, it is good that a test should be easy and cheap to construct, administer, score and interpret. We should not forget that testing costs time and money that could be put to alternate uses.