Designing an Experiment

Caroline decides to save money by switching to a generic brand of dog food for Schnookum and Schnozzer, her mastiffs. After several days of eating the new food, however, the dogs stop sleeping through the night. They whine and tug at Caroline's blankets until she gets up to play with them. Caroline wants to know if this behavior is caused by their new food. For one week, she gives generic food to Schnookum, and she gives the original brand to Schnozzer. Schnookum continues to wake her up at night, but Schnozzer sleeps all night.

Gabby loves long-distance running, but her feet develop terrible blisters. Some of her track teammates suggest that the blisters are caused by her cotton socks, which absorb moisture. Gabby borrows a pair of double-layer running socks made of a synthetic blend. For two weeks she wears the synthetic socks when running, and for the following two weeks she switches back to the cotton socks when running. During this month, Gabby counts the number of blisters she develops. She finds that she has only one blister while wearing synthetic socks, but five blisters while wearing the cotton socks.