Measurement in the Testing of Ideas

1. A construct is simply an idea, concept, or theoretical abstraction, which has multiple referents that in psychology are known as measurable variables.
2. To “play” with theoretical constructs, such as intelligence, happiness, and personality, requires objective instruments of measurement. No one measurement can fully capture a construct.
3. A tool of measurement is judged by the extent to which it provides reliable (consistent) and valid (meaningful) scores.
4. The correlation coefficient statistic is used to assess reliability and validity.
5. A reliable instrument is internally consistent and stable over time, as reflected by high interitem and test–retest reliability coefficients.
6. An instrument has convergent validity when it correlates with other measures of the same construct, and it has discriminant validity when it does not correlate with measures of a different construct.