Kenny Performed an Experiment on the Effects of After-School Educational

Multiple Choice

Kenny performed an experiment on the effects of after-school educational activities on students' academic performance.His experimental group involved after-school educational activities and his control group involved after-school non-educational activities.The children in the control group felt left out and gave up on the experiment.Which source of internal invalidity is reflected?

A) instrumentation
B) testing
C) statistical regression
D) demoralization
E) history