A group of children with emotional disorders is placed in a special program to improve the quality of their social interactions based on their extreme test scores. At the end of the program, the...

A group of children with emotional disorders is placed in a special program to improve the quality of their social interactions based on their extreme test scores. At the end of the program, the average increase in the quality of their interactions is 57%. What threat to internal validity negates the value of this finding, and what can you do to remedy the situation?