Given below are two statements, one is labelled as Assertion A and the other…

Concept

A history threat to internal validity arises when an event outside the intervention occurs during a study and changes participants or measured outcomes.

That change can be mistaken for an effect of the intervention, so history can seriously weaken or even invalidate the causal conclusion.

Application

Assertion A says that history effects can be fatal to a social research study. This accords with the definition: an intervening event can contaminate the observed change and undermine internal validity.

Reason R says that events occurring during a study do not affect respondents’ opinions and attitudes. This denies the causal pathway that makes history a threat; such events can affect respondents and the measured outcome.

Contrast

• “Both A and R are correct and R explains A” treats the no-effect claim as an explanation of a threat that depends on an effect.

• “Both A and R are correct but R does not explain A” still accepts R’s no-effect claim, which conflicts with the definition of a history threat.

• “A is correct but R is not correct” preserves the history threat and rejects the denial of its event-to-response mechanism.

• “A is not correct but R is correct” removes the history threat and accepts the no-effect premise, contrary to the research-design definition.

Therefore, A is correct but R is not correct.