A Scientific Method for your Science Experiment

1. Select a Question

Your question should be asked in a way that cannot be answered with a simple “yes” or “no.”  


“How does light affect the growth of plants?” is a better question than “Does light affect the growth of plants?”

2. Form a Hypothesis

This is a prediction about what will happen in your experiment.  This step can be easier if you have visited the library and found other experiments that are similar to the one you want to do.


Plants may grow to different heights if light comes from the top, sides, or both. Top lighting should be better than lighting from the sides.

3. Do the Experiment

 Plan the details of your experiment.   Decide which thing you will change on purpose (the manipulated variable) and what will change because of this (the responding variable).  The change in the responding variable should be one that can be measured.  Also decide which things you must keep the same (the controlled variables).  Think about:

  • What will you be measuring?
  • How will you measure it?
  • How many tests will you do?
  • What will be recorded?


  • What is changed (manipulated variable): direction of light
  • What changes because of this (responding variable): height plant grows in a certain amount of time
  • What stays the same (controlled variables): type of plant, length of time in light, amount of light, size of pot, type of soil, amount of water

4. Prepare the Results

Organize the measurements you have made to show what happened.  Wherever possible, use numbers to show your results.  Charts, graphs and tables are good ways to show your results.

5. Explain the Results

Spend some time thinking about what the numbers mean.  Try to explain how or why the results came out as they did. What was the cause?  Do the results agree with your hypothesis?

6. Draw Conclusions

What can you say about your experiment in general?  What can you count on happening again if someone else does a similar experiment?