A threat to internal validity that occurs when a measuring instrument changes over time due to prior use is called what?

A threat to internal validity that occurs when a measuring instrument changes over time due to prior use is called what?

• A. Instrumentation threat
• B. Maturation
• C. History
• D. Demand characteristics

Answer: (A)

Instrumentation threat arises when the tool or observer used to measure the outcome changes over time because of prior use. This drift can come from the instrument being revised, scoring rules being altered, or the rater becoming more lenient or stringent as they gain experience. When the measurement method itself changes, observed differences in the dependent variable may reflect shifts in the instrument rather than true changes in the construct, threatening internal validity. For example, if a behavior checklist is reworded between pretest and posttest, or if a clinician’s scoring criteria drift with repeated use, the scores might change due to the instrument rather than because participants truly changed. This differs from maturation (natural changes in participants over time), history (external events affecting outcomes across groups), or demand characteristics (participants guessing the study aims and changing responses accordingly).

Instrumentation threat arises when the tool or observer used to measure the outcome changes over time because of prior use. This drift can come from the instrument being revised, scoring rules being altered, or the rater becoming more lenient or stringent as they gain experience. When the measurement method itself changes, observed differences in the dependent variable may reflect shifts in the instrument rather than true changes in the construct, threatening internal validity.

For example, if a behavior checklist is reworded between pretest and posttest, or if a clinician’s scoring criteria drift with repeated use, the scores might change due to the instrument rather than because participants truly changed. This differs from maturation (natural changes in participants over time), history (external events affecting outcomes across groups), or demand characteristics (participants guessing the study aims and changing responses accordingly).