Perceiving that there is the same amount of modeling clay as before when it is rolled out into a Tootsie Roll shape is known as ______

A systematic, step-by-step procedure that guarantees a solution to a problem of a certain type is called __________

a) trial and error. b) an algorithm. c) means-end analysis. d) working backwards.

A researcher goes to great lengths to ensure that the proportion of males and females in his study matches the proportion of males and females nationally. He is selecting a ______ sample

a. random b. controlled c. biased d. representative