What would be the most likely threat to internal validity for adult's anxiety and depression scores during the decade of 1929-1939, known for the stock market crash?

Question

Quizplus · Accepted Answer

The most likely threat to internal validity for adult's anxiety and depression scores during the decade of 1929-1939 would be the history effect, because this period was known for the stock market crash and the Great Depression, which could have had a significant impact on participants' mental health, with or without the intervention or treatment being studied. The other options (testing effect, instrumentation, and sensitization effect) are not as relevant or likely to affect internal validity in this specific scenario.

What Would Be the Most Likely Threat to Internal Validity