GOOGLE Science Fair
Tipsheet #6 – Variables
A successful science fair project requires a good deal of careful planning. This planning will enable you to avoid some common difficulties and will keep your project on track.
· In order to plan effectively, you will need to understand the role variables play in your project.
· Your next step is to determine what equipment and supplies you will need. Make a materials list using metric amounts. Check all materials that you have access to at home or through a parent’s work. Another possible source for materials is district High Schools and Colleges in the area. It is your responsibility to find what you need, but I will help you if you ask.
· A very important part of planning for your project is deciding exactly what you will measure and exactly how you will measure it. You will need to discuss this aspect with your teacher.
Explanations of each kind of variable follows:
Independent Variable (What do I change): The cause of the change in your research is the Independent variable. In your experimentation, you will vary one factor to observe what will happen. The thing you vary is the manipulated variable. In our sample project, the different level of fertilizer is the Independent variable.
Dependent Variable (What do I observe): You change one factor to observe what will happen to something else. The “something else” is the dependent variable, the effect. In our sample project, the Dependent variable is the growth rate of the algae.
In an effective experiment there must be “controls” in place to ensure that the dependent variable is the only cause of the change in the experiment. These controls are extremely important and help to improve the quality of your findings. If they are not described and followed in the experiment, you may find it very difficult to come to valid conclusions. Two types of controls are described below:
Controlled Variable: All factors that could affect your results and must be kept constant are called controlled variables. In the sample project, the controlled variables are the type and source of algae grown, the temperature, the amount of sun, the amount of medium (water without the different concentrations of fertilizer), size of the containers, etc.
Control Group: Controlled experiments are designed to determine cause and effect. There must be a standard to which the experimental data can be compared. You must have a control group in order to compare the results of the experimental groups. A control group is free of any change from the independent variable. In the sample project, the control group is kept in a medium without any fertilizer, while the experimental groups are kept in the same growth medium with different levels of fertilizer added. This is the natural group or what naturally occurs for variable. Some experiments may not have a control group.
Repeated trials: In an effective experiment there should be repeated trials. Repeated trials are additional attempts under the same experimental conditions to produce similar results. Additional trials show that your initial data did not arise by accident nor is a “fluke” caused by some other variable. All experiments should include at least 2 and at most 5 trials for each experimental condition.
If you are working with plants or animals and are measuring over time (growth, color, etc.), then repeat trials should be conducted during the same time frame as the initial test subject.
Variables
Equipment
1. The Independent variable is ____________________
The units it will be measured in are ___________________.
It will be measured with these instruments: ___________________________________
______________________________________________________________________
2. The Dependent variable is _______________________
The units it will be measured in are ___________________
It will be measured with these instruments: ___________________________________
______________________________________________________________________
3. List all the controlled variables and how you will keep them constant
Controlled variable How to keep constant
a. ______________________ ________________________________________
b. ______________________ _________________________________________
c. ______________________ ________________________________________
d. ______________________ ________________________________________
e. ______________________ ________________________________________
4. Describe your Control Group: _________________________________________________
______________________________________________________________________________
______________________________________________________________________________
5. (If applicable) List the organisms you plan to use and their scientific names (scientific name refers to the Genus species and should be underlined.)
Common Name Genus/species
1. _______________________________ ______________________________
2. _______________________________ ______________________________
6. Describe the number of repeated trials and when you plan to do them.
__________________________________________________________________________
__________________________________________________________________________
___________________________________________________________________________
7. List all the chemicals you plan to use:
__________________________________________________________________________
__________________________________________________________________________
___________________________________________________________________________