Threats to internal validity – UGC NET Question

Statements A, B, C, D and F correctly describe threats to internal validity, while E is false. Statement A is true because events between measurements can influence outcomes. Statement B is correct as maturation refers to participant changes over time, and statement C rightly defines the testing effect. Statement D accurately explains instrumentation changes, and statement F is true for attrition or mortality, whereas E is false because random assignment is a control technique that strengthens, not threatens, internal validity.

Option A:
Option A includes all the genuine threats named (A, B, C, D and F) and excludes E, which misinterprets the role of random assignment. It thus presents a complete and accurate set of internal validity threats mentioned in the list. Therefore this option is the correct answer.

Option B:
Option B leaves out F, ignoring the issue of differential dropout across groups. Since attrition can seriously bias results, omitting it gives an incomplete picture of internal validity threats. As a result, this combination is not acceptable.

Option C:
Option C contains E in addition to B, C, D and F, thereby treating random assignment as a threat. This is incorrect because random assignment is used to control extraneous variables and enhance internal validity. Including a false statement disqualifies this option.

Option D:
Option D omits B, which is an important threat related to participant changes, and therefore fails to recognise the full range of threats in the list. By leaving out a true statement, it offers only a partial account and cannot be considered correct.