Step 4: Plan Your Investigation

Procedure

Write the experimental procedure like a step-by-step recipe for your science experiment. A good procedure is so detailed and complete that it lets someone else duplicate your experiment exactly! Repeating a science experiment is an important step to verify that your results are consistent and not just an accident. For a typical experiment, you should plan to repeat it at least three times (more is better). If you are doing something like growing plants, then you should do the experiment on at least three plants in separate pots (that's the same as doing the experiment three times). If you are doing an experiment that involves testing or surveying different groups, you won't need to repeat the experiment three times, but you will need to test or survey a sufficient number of participants to insure that your results are reliable. You will almost always need many more than three participants!


What Makes a Good Experimental Procedure? For a Good Experimental Procedure, You Should Answer "Yes" to Every Question

1. Have you included a description and size for all experimental and control groups? 

2. Have you included a step-by-step list of all procedures?

3. Have you described how to the change independent variable and how to measure that change? 

4. Have you explained how to measure the resulting change in the dependent variable or variables? 

5. Have you explained how the controlled variables will be maintained at a constant value?

6. Have you specified how many times you intend to repeat the experiment (should be at least three times), and is that number of repetitions sufficient to give you reliable data?

7. Can another individual duplicate the experiment based on the experimental procedure you have written?


Materials List

What type of supplies and equipment will you need to complete your science fair project? By making a complete list ahead of time, you can make sure that you have everything on hand when you need it. Some items may take time to obtain, so making a materials list in advance represents good planning!

Make the materials list as specific as possible, and be sure you can get everything you need before you start your science fair project.