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
- List the steps for your experiment. Be as systematic and
thorough as possible, listing everything you will require for the
- 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.