Validity is an important characteristic of an instrument. It refers to the ability to measure, in a test, what was intended so that users can interpret the outcomes.
There are five types of evidence to demonstrate validity of test scores:
Threats to Internal Validity: Controlling extraneous variables will help the research to attribute the observed outcomes to the intervention. Factors affecting internal validity are:
Threats to External Validity: This refers to the extent outcomes from a study can be applied to other individuals and settings. Factors affecting external validity are:
References:
Gay, L. R., and Airasian, P. (1997). Educational research. New Jersey, Ohio: Merrill.