Explanation about both validity and reliability has been made by Dr Teoh. From there, we can know the real meaning of validity that is as referringto the appropriateness, correctness, meaningfulness, and usefulness of the specific inferences researchers make based on the data they collect. There are three types of validity
i) Content-related evidence of validity
- the content and format of the instrument. How appropriate is the content? how comprehensive? Does it logically get at the intended variable? How adequately does the sample of items or questions represent the content to be assessed? Is the format appropriate? The content and format must be consistent with the definition of the variable and the sample of subjects to be measured.
ii) Criterion-related evidence of validity
- the relationship between scores obtained using the instrument and scores obtained using one or more other instruments or measures (often called a criterion). How strong is this relationship? How well do such scores estimate present or predict future performance of a certain type?
iii) Construct-related evidence of validity
- the nature of the psychological construct or characteristic being measured by the instrument. How well does a measure of the construct explain differences in the behavior of individuals or their performance on certain tasks? We provide further explanation of this rather complex concept later in the chapter.
Reliability refers to the consistency of the scores obtained—how consistent they are for each individual from one administration of an instrument to another and from one set of items to another.
Reference :
Fraenkel, J.R. & Wallen, N.E. (2012) How to Design and Evaluate Research Education. New York: McGraw Hill Inc.
