1. Test Characteristics
Good test should have at least three characteristics namely validity, reliability, and practically. Another characteristics i.e. discriminating, will be added later.
Validity: a test is said to be valid if it measure what to be measured. There are several types of validity namely:
1. Face validity which indicates that a test look valid to other testers especially its appearance, composition, items, organization, and contents.
2. Content validity indicates that the test reflects what the students have learned or the contents of the curriculum.
3. Empirical validity which shows that the results of the test have high correlation with the results of the valid criterion measure.
4. Concurrent validity when the result of the test is correlated with the present results of valid rating or test.
5. Predictive validity when the results of the test are highly correlated with the results of later valid measurement.
6. Construct validity is indicated by the test ability to measure specific characteristics in accordance with the theory of language behavior or language learning.
Reliability, a test is
said to be reliable if it can produce stable or consistent scores although the test is administered at different times. Reliability is a very important characteristic of a test a test is not valid unless it is reliable. There are some factors which affect the reliability of a test, namely the sample performance, the number of items, the administration of the test, the student motivation and other factors beyond the control of the tester (such as student sickness etc.).
There are several techniques of estimating the reliability of a test.
a. By using test retest technique. A test is used twice and then the results are correlated to see the consistency of measuring.
b. By using parallel forms of the same test. Both are administered and then the results are correlated. The coefficient of correlation will indicate the reliability of the test.
c. Split-half technique with which a test is divided into two and then the both are correlated using a particular formula. The results will indicate the whole reliability of a test.
Other characteristics of a good test is practically which involves considering some factors when selecting the test, namely economy, ease of administration, and ease of interpretation. Economy involves considering whether the test will take a long time to administer and to score. Ease of administration involves the consideration of whether the test is easy or complicated to administer. Ease of interpretation includes the considering of the reliability, the validity, and norms for appropriate reference group. Finally, the characteristic of a good test is discriminating which refers to the capacity of the test to discriminate among the testees performances that is differentiate the bright from the low candidates.
Ease of administration involves the consideration of whether the test is easy to administer. Whether the test needs complicated electronic equipments and also whether the test is easy to score. These two considerations affect the practically of a test.
Ease of interpretation includes the consideration of that reliability and validity and the norms for appropriate reference group. Especially when you use standardized test you have to get some definite information about these all. Finally the characteristic of a good test is “discrimination”. According to Heaton (1989) it is “its capacity to discriminate among the different candidates and to reflect the differences in the performances of the individual in the group”. For example if you test 40 student and 70% of them get 70 and very little get below or above 70 then your test it is not discriminating.