Instrumentation as a Threat to Internal Validity

Instrumentation, as a threat to internal validity, refers to changes in the established measurement system during a study that may be responsible for an observed effect. The soundness of inferences that can be made is susceptible to bias from instruments, observers, scorers, or participants themselves throughout the research process. For example, springs in a scale might become weaker over time, depressing farther than they should, artificially increasing a person’s weight, or an observer making a judgment on students’ performance may begin to notice emotional states as they watch students interact, altering the scores that are awarded. Simply put, this threat to internal validity is a change in how the dependent variable of a study is scored that is not related to the variables that are ...