The previous five chapters have given advice on the testing of different abilities. The assumption has been that we need to obtain separate information on each of these abilities. There are times, however, when we do not need such detailed information, when an estimate of candidates' overall ability is enough.

One way of measuring overall ability is to build a test with a number of components: for example, reading, listening, grammar and vocabulary. Specifications are written for the individual components and these are incorporated into specifications for the entire test, with an indication of the weight that each of the components will be given. The scores on the different components of the test are added together to give an indication of overall ability. This is what happens in many proficiency tests. Even if the scores on the individual components are given, they may be ignored by those who use the test scores.

But building a big test of this kind is hardly economical if we simply want to use test results for making decisions that are not of critical importance and in situations where backwash is not a consideration. One obvious example of this is placement testing in language schools. Typically, all that is asked of language school placement tests is that they assign people to a level in that school. If people are misplaced by the test, they can usually easily be moved to a more appropriate class; provided that not too many such moves are called for, this is not a problem.