Which statement about internal validity threats is true?

• A. Maturation is the change in participants over time; history is events outside the study that can influence outcomes.
• B. Maturation refers to external events outside the study.
• C. Instrumentation threat involves measurement changes; random assignment affects internal validity.
• D. Selection bias is about measuring the wrong variable.

Answer: (A)

Internal validity threats are factors that can produce changes in the dependent variable that aren’t caused by the experimental manipulation. Maturation means natural changes in participants over time—like aging, developing skills, or growing tired or bored—which can affect results in studies with repeated measurements. History refers to events outside the study that occur between measurements and could influence outcomes for participants as a group, such as a news event or policy change. The statement is true because it accurately defines these two common internal validity threats. Other options mix up these concepts—for example, maturation is not external events, instrumentation threat involves changes in how measurements are made or who is making them, and selection bias concerns how participants are chosen or assigned rather than what is being measured.