People diagnosed with schizophrenia are randomly assigned to either an attention-training group or a social skills training group. Equal numbers of males and females were in each training group. Scores on a measure of thought disorder, a prominent symptom in schizophrenia, were examined after the end of the training sessions. In addition, there was a no-schizophrenia group. This study was a(n) ________________ design.
A) Mixed
B) Pure experiment
C) Correlational
D) Epidemiological