A researcher plans a special series of classroom lessons designed to increase students' verbal skills.A control group does not have the lessons.Which of the following would most likely be threats to internal validity?
A) History
B) Hawthorne effect
C) Teacher expectations effect
D) Mortality
E) b and c

Question

Quizplus · Accepted Answer

Both the Hawthorne effect (where participants alter their behavior because they know they are being observed) and the teacher expectations effect (where teachers unknowingly treat students differently based on their expectations) could affect both the control and experimental groups, as they are not specific to the treatment group. Hence, they are threats to internal validity. History (outside events that could affect the outcome) and mortality (loss of participants during the study) are also threats to internal validity, but they would only affect one group (either the treatment or control group) and not the other.

A Researcher Plans a Special Series of Classroom Lessons Designed