A Researcher Wants to Know Whether Wearing Sunglasses Improves Driving

Multiple Choice

A researcher wants to know whether wearing sunglasses improves driving performance. In a properly designed WITHIN-subjects experiment, presence or absence of sunglasses would be varied by

A) randomly assigning half the drivers to a sunglasses condition and half to a no-sunglasses condition.
B) having all drivers first drive without sunglasses and then with sunglasses.
C) having half the drivers first drive without sunglasses and then with sunglasses and having the other half first drive with sunglasses and then without sunglasses.
D) having all drivers first drive with sunglasses and then without sunglasses.