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Mike the zookeeper wants to know how to make elephants jump higher. He feeds one group extra high-protein food, and decides to also replace their water with vitamin water. The other group gets normal food and normal water. After observing both groups, Mike concludes that extra high-protein food makes them jump higher, and probably works on people, too.
What is wrong with the way he set up his experiment?
Too many independent variables! He should only change ONE factor and leave the rest the same (not the food AND the water)