A ball is rolled on different surfaces and the distance travelled is measured. What type of variable is the distance?

Correct answer: Dependent variable

The direct answer is A, the dependent variable. The surfaces are deliberately different, so surface type is the independent variable. The distance travelled is observed and measured after the ball rolls, so it is the response to the surface. Step by step: change the surface; roll the ball under the same starting conditions; measure how far it travels; distance may change because the surface changes; therefore distance is dependent. A is correct. B is wrong because the independent variable is what is deliberately changed, namely the surface, not the measured distance. C is wrong because a controlled variable must be kept the same, such as ball, starting point, push, and slope. D is wrong because distance is not a constant if it varies between surfaces; “constant” means unchanged. A fair test also repeats trials and uses the same method. Memory cue: changed factor is independent; measured result is dependent.