George wants to know if the amount of water he uses on his plants will affect their growth. he buys three of the same plants and puts them in the same size pot with the same type of soil. he puts all three plants in the same place outside. he then waters the first plant with ¼ cup of water every day, the second plant with ½ cup of water every day, and the third plant with 1 cup of water every day. he does this every day for a month and measures all of the plant’s heights every week. he discovers that after one month the plant with ½ cup of water grew taller than the other two plants.
what is one constant variable in this experiment?