The Function of Test
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supposed to measure”. The word ‘construct’ refers to any underlying ability or trait which is hypothesized in a theory of language ability. One might
hypothesis, for example, that the ability to read involves a number of sub- abilities, such as the ability to guess the meaning of unknown words from the
context in which they are met. It would be a matter of empirical research to establish whether or not such a distinct ability existed and could be measured. If
we attempted to measure that ability in a particular test, then that part of the test would have construct validity only if we were able to demonstrate that we were
indeed measuring just that ability. Brown 1996 adds that a construct, or psychological construct as it is also called, is an attribute, proficiency, ability, or
skill that happens in the human brain and is defined by established theories. Construct validity has traditionally been defined as the experimental
demonstration that a test is measuring the construct it claims to be measuring. Such an experiment could take the form of a differential-groups study, wherein
the performances on the test are compared for two groups: one that has the construct and one that does not have the construct. If the group with the construct
performs better than the group without the construct, that result is said to provide evidence of the construct validity of the test.
This idea is also supported by McNamara 2004, he said that construct mean the underlying ability or trait
being measured by the test. Campbell and Stanley 1966 states that construct validity can be considered as labels that assign meanings to the test we are
measuring.
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2. Content validity A test is said to have content validity if its content constitutes a representative
sample with which it is meant to be concerned Hughes, 1989: 22. A test is designed to measure mastery of a specific skill or the content of a particular
course of study, and we can expect the test to be based upon a careful analysis of the skill or an outline of the course. Content validity includes any validity
strategies that focus on the content of the test. To demonstrate content validity, testers investigate the degree to which a test is a representative sample of the
content of whatever objectives or specifications the test was originally designed to measure. To investigate the degree of match, test developers often enlist well-
trained colleagues to make judgments about the degree to which the test items matched the test objectives or specifications Brown 1996: 231-249. Heaton
1975: 154 adds another aspect to consider about content validity. He says “the test should be so constructed as to contain a representative sample of the course,
the relationship between the test items and the course objectives always being apparent”. In other words, content validity also measures how the test item meets
the course objectives. 3. Face validity
Hughes 1989: 27 states that a test is described as having face validity if it looks right or as if it measures what it is supposed to measure. Face validity is hardly a
scientific concept, yet it is important. It is often useful to show the test to other people so that possible absurdities and ambiguities can be discovered Heaton,
1975: 152.
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Instead of validity and reliability as the essential characteristics of a good test, usability also important. The usability of a test includes the ease and time
administration, the scoring, the interpretation and application, and the cost. Valette 1967 says that the essential requirements of a good test are reliability and validity.
Since those two criteria are the most important.