Dr Hyper Treated 20 Patients Using a New Therapeutic Procedure

Multiple Choice

Dr. Hyper treated 20 patients using a new therapeutic procedure. An outside observer rated the children's activity level on a laboratory task before and after the treatment; 80% of the children decreased their activity level following treatment, and Dr. Hyper concluded that the procedure was highly effective. In Dr. Hyper's experiment, what is the independent variable?

A) The children's diagnosis as hyperactive or not
B) The presence of the observer
C) The new therapeutic procedure
D) The children's activity level