What percentage of adolescents who use illegal drugs have used marijuana in the past?

Whereas internal validity refers to _________, external validity refers to _________

a. practical conclusions; statistical conclusions b. the relationship between the independent and the dependent variable; the extent to which the findings are expected to generalize c. the extent to which the findings are expected to generalize; the relationship between the independent and the dependent variable d. statistical conclusions; practical conclusions

Shane, an eight-year-old, is the most notorious child in his class. He does not listen to his teachers, speaks loudly while the teacher is teaching, bullies other and hits children, and refuses to sit down in his seat. Dawson is most likely suffering from _____.

A. ADHD B. autism C. phenylketonuria D. Huntington's disease