The aims of diagnosis are to analyse the difficulties of the student in a particular phase of work. The aims is to reveal reliable information concerning his weakness in order to overcome them by concentrated action and for remedial teaching It can also be used as an inventory test to find out how much the student knows about a given phase of the subject matter. Diagnostic tests are used to discover and analyse pupil’s difficulties with a view to setting up specific remedial measures to correct errors and remove difficulties.
A diagnostic test is different from the achievement test in commerce. The main purpose of diagnostic test is to study the nature of difficulties experienced by pupils. While constructing a diagnostic test the teacher has to consider the individual difficulties experienced by students in solving problems. The test items should also give due consideration to the varying abilities of pupils in solving different types of problems. The age-norm, the grade norm etc. should also be given due consideration. Before constructing such a test a pilot study be conducted over a given area or unit and its results statistically analysed before finalising the test.
The reliability co-efficient of the test has to be calculated and then the diagnostic test can be deemed to be fit for administration over a large sample.
Appropriate remedial instructions be given and for this careful planning is essential. The causes of failure in solving a problem are to be hypothesized systematically.
The importance of diagnostic tests is due to the following
(i) Nature of the subject-matter,
(ii) Difficulties experienced by students as a group, and
(iii) Difficulties experience by certain individuals.
An achievement test is used to measure the degree of mastery of skills, fundamental concepts, process, and general knowledge of the subject, attained by the student. The achievement test is valid when it can measure the extent to which the purpose which it has been constructed.