The Experiment

The control group

A control group is one where the independent variable is at a "default" or "natural" value or state. In our sunscreen lotion experiment, for example, the control group will consist of at least one experiment where no sunscreen lotion is used at all. Once you have a reading on your UV meter where no sunscreen lotion is used, this reading forms a base-comparison for the rest of your trials.

Steps to designing your experiment:

  • Identify and describe the independent, dependent and control variables
  • List the steps for your experiment. Be as systematic and thorough as possible, listing everything you will require for the experiment.
  • Be clear about how you will measure the changes in the independent and dependent variables.
  • How are you going to ensure that the experiment constants (control variables) are maintained/unchanged? For example, if one of the constants is temperature and lighting conditions, you could ensure that these are constant in an air-conditioned room with blackout curtains and indoor lighting.
  • Ascertain how many times your experiment will be repeated, in order to obtain accurate/reliable results.
  • Think of the safety issues and procedures to be observed at all stages of your experiment.
Next: Materials