Construct validity http://www.socialresearchmethods.net/kb/consthre.htm
What is construct validity • Construct validity refers to the degree to which inferences can legitimately be made from the operationalizations in your study to the theoretical constructs on which those operationalizations were based. • Construct validity involves generalizing from your program or measures to the concept of your program or measures.
Threats to construct validity (1) • Inadequate Preoperational Explication of Constructs • preoperational means before translating constructs into measures or treatments, and explication means explanation -- in other words, you didn't do a good enough job of defining (operationally) what you mean by the construct
Threats to construct validity (2) • Mono-Operation Bias • Mono-operation bias pertains to the independent variable, cause, program or treatment in your study -- it does not pertain to measures or outcomes • Mono-Method Bias • Mono-method bias refers to your measures or observations, not to your programs or causes • Interaction of Different Treatments • The result might be the combination of the separate programs they participated in not only yours.
Threats to construct validity (3) • Interaction of Testing and Treatment • Does testing or measurement itself make the groups more sensitive or receptive to the treatment? If it does, then the testing is in effect a part of the treatment, it's inseparable from the effect of the treatment. • Restricted Generalizability Across Constructs • unintended consequences • Confounding Constructs and Levels of Constructs • Slight increases or decreases of the dosage may radically change the results.
Threats to construct validity (4) • The "Social" Threats to Construct Validity • Hypothesis Guessing • Participants are likely to base their behavior on what they guess about the study, not just on your treatment. • Evaluation Apprehension • Many people are anxious about being evaluated. ( performed good and poorly) • Experimenter Expectancies • Sometimes the researcher can communicate what the desired outcome for a study might be (and participant desire to "look good" leads them to react that way). For instance, the researcher might look pleased when participants give a desired answer. If this is what causes the response, it would be wrong to label the response as a treatment effect.
External validity • External validity refers to the approximate truth of conclusions the involve generalizations. Put in more pedestrian terms, external validity is the degree to which the conclusions in your study would hold for other persons in other places and at other times.
Threats to External Validity • A threat to external validity is an explanation of how you might be wrong in making a generalization • Time, place, people, setting.
Improving External Validity • based on the sampling model, suggests that you do a good job of drawing a sample from a population, • such as random selection. • use the theory of proximal similarity more effectively. • do your study in a variety of places, with different people and at different times.
Conceptualizing and controlling for threats to validity • Selection bias expand or purify the experiment group. • Generality of the findings viewing simple designs as portions of potentially larger design. • Once again, construct validity and external validity heteromethod replication.