Validity is the most critical
criterion and indicates the degree to which an instrument measures what it is
supposed to measure. Validity can also be thought of as utility. In other
words, validity is the extent to which differences found with a measuring
instrument reflect true differences among those being tested. But the question
arises: how can one determine validity without direct confirming knowledge? The
answer may be that we seek other relevant evidence that confirms the answers we
have found with our measuring tool. What is relevant, evidence often depends
upon the nature of the research problem and the judgement of the researcher.
But one can certainly consider three types of validity in this connection: (i)
Content validity; (ii) Criterion-related validity and (iii) Construct validity. (Khotari; 2004; 75) .
Reliability
The test of reliability is
another important test of sound measurement. A measuring instrument is reliable
if it provides consistent results. Reliable measuring instrument does
contribute to validity, but a reliable instrument need not be a valid
instrument. For instance, a scale that consistently overweighs objects by five
kgs., is a reliable scale, but it does not give a valid measure of weight. But
the other way is not true i.e., a valid instrument is always reliable.
Accordingly reliability is not as valuable as validity, but it is easier to
assess reliability in comparison to validity. If the quality of reliability is
satisfied by an instrument, then while using it we can be confident that the
transient and situational factors are not interfering (Khotari; 2004; 75).
Referensi
Khotari.C.R 2004; 75) Research Methodologi Methods and Tehnicques. New Age International (P) Ltd., Publishers: Ansari Road,
Daryaganj, New Delhi - 110002
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