Light is focused on the retina by the ______

In a true experiment, the researcher _______ variables, and in a quasi-experiment the researcher _______ variables

a. manipulates, observes b. observes manipulates c. controls, assigns d. assigns, records

Approximately __________ percent of children are right-handed, whereas __________ percent of children are left-handed

a) 90; 10 b) 75; 25 c) 25; 75 d) 10; 90