The _____ theory of sleep (sometimes called the _____ theory) proposes that sleep is necessary to keep humans out of harm's way during the night

As experimental control increases:

a. external validity decreases. b. external validity increases. c. the more relevant the study to real-world problems. d. we become less able to rule out alternative hypotheses.

Approximately 85% of all people who are diagnosed with intellectual disability fall into the __________ subtype

A) mild B) moderate C) severe D) profound