Describe the variables used in your experiment. The data sheet(s) of your experiment records should be included.
“Example: The variable I used for my experiment was plant growth in different lights.
One plant variable was in complete sunlight and the other in complete darkness…”

Parents and students may wish to refer to Janice VanCleave’s Science Fair Handbook
available in paperback at most bookstores or online at

“Project experimentation is the process of testing a hypothesis: things that have an effect on the experiment are called variables. There are three kinds of variables that you may identify in your experiments: independent, dependent and controlled.
The independent variable is the thing you purposely may (change) in the experiment.
The dependent variable is the thing being observed which changes because of the independent variables.
The control variables are that things that are not changed or are kept the same in an experiment

For example: An experiment involving the growth of mold on bread concerns the effect of light on the reproduction of bread mold.
The independent variable for the experiment is light and the dependent variable is bread mold growth that is a test.
The controlled conditions are kept the same in the experiment - for example, the room temperature and humidity—and the brand of the bread used is kept the same. In the experiment set up the conditions by placing three or four pieces of the same kind of white bread in cardboard boxes that are the same size (of a breadbox), one slice in each box. Close all the boxes so that they receive no light.
If at the end of the time period, mold grows, you might decide that no light is needed for mold reproduction. But before making this decision, you find out if the mold would grow with light. The control groups must be set up of bread that receives light through the testing period. Do this by placing an equal number of loaves in comparable-size boxes, but leave them open.

For example In a test with racing cars down a ramp testing surface tension:
The control variables are using the same racing car, using the same length and incline on the ramp.
The independent variable is the different surfaces used on the ramp- hard board, carpeting, and sand
The dependent variable is the speed/ distance the car travels down the ramps of different surfaces.

For Example: In a project testing a plant’s need for sunlight to measure plant growth:
The control variables are using the same kind of plant, same amount of water, same room temperature.
The independent variable is the amount of light each plant receives, 1 in sunlight, and 1 in a dark corner.
The dependent variable is the health of the plant and how much the plants grow over the time of the test.

Do have only one independent variable during an experiment.
Do repeat the experiment more than once to verify your results.
Do have a control variable. Do have more than one control, with each being identical.
Do organize data. Into a chart, table or graph. - it looks good on your display board.
Gather your materials to do the test in advance.
Give yourself enough time to do the test. For example, you would need plenty of time to build the ramps or measure plant growth in the above experiments. Could you do this experiment at this time of year?
Good Luck!