Wendy added the same amount of water to two plants of the same variety, placed them in the sun and added fertilizer to one plant but not to the other. This was done to check the height of the plants in the presence and absence of the fertilizer. A dependent variable is a variable which is being tested and measured in a scientific experiment. The dependent variable in the above experiment is the height of the plant or the growth of the plant. The height of the plant is being tested and measured. An independent variable in an experiment is the variable that is changed or controlled in a scientific experiment to test the effects of the dependent variable. The independent variable is the fertilizer which is used to check the height of the plant which forms the dependent variable.