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Johnny wanted to determine the effect of water on plant growth. To do this, he planted 2 flowers in a pot with the same amount of water. He put Plant A in the window near the sun, and Plant B in the closet so it received no sunlight. Then he watered Plant A twice a day, and Plant B three times a day.
Why is this not a fair experiment?
This is not a fair experiment because you are changing 2 variables - the amount of sunlight and the amount of water. You don't know if the sunlight or the water is having the effect on the plant.
What would Johnny have to do to make this a fair experiment?