Instrumentation threat measurement change – UGC NET Question

The instrumentation threat arises when measurement conditions are not equivalent across occasions, such as when instruments are recalibrated or observers become more lenient or strict over time. These changes can create apparent differences in scores that are unrelated to the treatment. As a result, it becomes difficult to determine whether observed effects are due to the intervention or to altered measurement. Therefore, the situation described in the stem is called instrumentation.

Option A:
Instrumentation problems can be reduced by standardising procedures, training observers, and checking calibration regularly. When such precautions are ignored, internal validity is compromised because score changes may reflect measurement drift rather than true change in participants. This focus on changes in instruments or scoring matches the stem, making this option correct.

Option B:
History refers to external events occurring between measurements that affect participants’ performance and is conceptually distinct from changes in measurement tools.

Option C:
Mortality, or attrition, occurs when participants drop out of the study, potentially biasing results if those who leave differ from those who remain. It does not involve changes in instruments or scoring.

Option D:
Selection threats arise when groups differ systematically at the start of an experiment due to non-random assignment. While serious, they are not related to shifts in measurement conditions over time.