Ch. 9: Internal Validity

Ch. 9: Internal Validity

1. Meaning of Internal Validity

   • When a study lacks internal validity, one or more alternative hypotheses exist to explain the outcomes
     • These alternative hypotheses are referred to by researchers as threats to internal validity
   • When a study has internal validity, it means that any relationship observed between two or more variables is unambiguous, rather than being due to something else

2. Threats to Internal Validity

   • Some of the more common threats to internal validity are differences in subject characteristics, mortality, location, instrumentation, testing, history, maturation, attitude of subjects, regression, and implementation
     • The selection of people for a study may result in the individuals or groups differing

3. Controlling Threats to Internal Validity

   • Researchers can use a number of techniques or procedures to control or minimize threats to internal validity
     • Essentially they boil down to four alternatives: (1) standardizing the conditions under which the study occurs, (2) obtaining and using more information on the subjects of the study, (3) obtaining and using more information on the details of the study, and (4) choosing an appropriate design