In an experiment I have two groups of flowers, A and B. As a curious scientist I wanted to test the effects of fertilizer on plant growth. Group A was not given any fertilizer, while Group B was given fertilizer. I left all other conditions the same within each group such as amount of water, type of flower, and amount of sunlight. After three weeks of running this experiment I measured the height of each plant. My conclusion was that Group B flowers were taller than Group A flowers. After reading this scenario what is the independent variable?

The independent variable in an experiment is the variable that is changed or manipulated by the experimenter in order to bring about a measurable response.

In this experiment, the effects of fertilizer on plant growth is tested. Two groups: Group A and B were used. Group A was not given any fertilizer, while Group B was given fertilizer. This portrays that the experimenter is manipulating the FERTILIZER. Hence, the FERTILIZER is the independent variable.