What is the control variable for my experiment?

My experiment is comparing the speed of growth of beans in cotton wool and soil.


Essentially, do beans grow faster in cotton wool or soil?





I need to know my control variable as I am writing up my report now.|||The controlled variables are the things that you kept constant throughout the test. In your experiment, you have one independent variable - the growing medium (soil and cotton wool). This should be the only thing that was different between the two tests.





In order for your test to be valid and fair, you would have needed to use the same size pot for both the soil and cotton wool test, use the same amount of water and frequency of watering, expose them to the same amount of sunlight, keep them at the same temperature, use the same type of bean in each pot, and measure the plants at the same time. All of those things would be your controlled variables.





For examples of independent vs. controlled variables, check out the following website:


http://www.sciencebuddies.org/science-fa鈥?/a>