Answer:
c) It refers to how well a study measures what it was designed to measure.
Explanation:
Validity explains how well an instrument measures what it supposed to measure. The idea of validity revolves around effectiveness of an instrument in achieving what the instrument is designed for. The instrument can be a study, survey or measurement instrument itself. Validity has degree, from high to low.
For example, if a study is undertaken to measure happiness at old age really help the researcher to reach conclusion about the research focus, then we can say the study has high validity. Otherwise, we can conclude that it has low validity.
