Some Tips for Designing Your Experiment
These ideas were suggested by scientists of the Life Sciences Support Contact
at the Kennedy Space Center who have served as judges at local science fairs
for many years.
A successfull science fair project follows these steps:
1. Keep it Simple
2. Decide on Controls
3. Select a Sample Size
4. Moniter Your Time
5. Keep a Detailed Notebook
6. Collect Data
7. Formulate a Conclusion
8. Create the Final Presentation
Keep it Simple
Keep things as simple as possible. Many students think that they need
to have many variables in an experiment to make the experiment valid. This
is not the case. It's much better to test only one variable thoroughly than
to test many at once.
For example: If you are investigating the effects of freezing temperatures on
tropical plants, don't add different lighting sources or nutrients as well, keep
those constant and only vary the temperature.
Decide on Controls
All experiments need to have an appropriate control. A control is a standard
to test your experimental result against. The conditions you are inflicting on
your "subjects" is called the experimental variable. All experiments must have
a control and it is worth taking time to decide what a good control is for your
experiment.
For example: If you are studying the effects of freezing temperatures on tropical
plants you will want to keep some plants under "normal" condidtions while exposing
others to extreme temperatures. Keeping some plants under "normal" conditions
gives you a standard to compare your frozen plants' health to.
Select a Sample Size
You will need to test several "subjects" in your experiment. The number of
"subjects" you test is your sample size. Having a large sample size (both in
your experimental and control groups) helps you determine if what you observe
is due to your experimental variable or to chance.
For example: If you are studying the effects of freezing temperatures on tropical
plants you will want several plants in your control group and several in your
experimental group. This way you can "average" the control group observations and
the experimental group observations in order to determine if the effect is a fluke
or what normally happens.
Moniter Your Time
Repetition in a key element in a science fair project. You need to allow yourself lots of time to repeat the project. Also you need to give yourself time for complications - projects hardly ever go as planned. In some cases there may be unforeseen problems that necessitate you to completly start over or redesign your project.
Keep a Detailed Notebook
All good scientists keep notebooks while preforming experiments.
Write down everything you observe while preforming your experiment.
Don't assume you will remember the particulars later. Keep track of the dates
you take observations and, if applicable, the times.
Don't erase anything or cross anything out. Sometimes data and observations may
seem un-important or un-related to what you are testing, but they may be supporting
evidence for your conclusion in the end. Bottom line: You never know what will be
applicable to your conclusions so take detailed notes of everything.
Collect Data
You will want to keep track of both quantitative and qualitative observations.
Quantitative data is anything that can be writen as numbers: measurements, amounts, etc.
Qualitative data is things that cannnot be writen directly as numbers: color, smell, etc.
Qualitative words like "bigger" mean different things to different people making
reporting your results with just words confusing. Report data quantitativly when possible
(instead of "bigger" measure the actual growth of the plant with a ruler to reprot height
and width changes and/or taking a count of leaves). It is advantageous to create a scale
in order to represent your qualitative observations in quantitative ways.
For example: If you are observing a color change create a chart showing the different shades
of the color and each shade with a number (with lowest number paired with lightest shade).
Everytime you check for color change record it not only with words. but also using the scale
you constructed.
Formulate a Conclusion
Did the data you collected support your hypothesis? If not, that is a result too! It doesn't
mean the experiment didn't work, you just discovered the outcome was different than you
expected. You aren't out to "prove" your hypothesis necessarily, the entire point of your
project is to say, "here is what I thought would happen, and here is what actually happened."
Be sure to consider and explore other possible explanations for your results.
For example: You are testing the effect of freezing temperature on tropical plants and
you leave your experimental group outside overnight to be exposed to the freezing temperatures.
When you bring the plants back in to be compared against your control group you notice not
only are the experimental plants dying, but there are holes in their leaves. Freezing
temperatures may not be the only variable causing your plants to die, there might be some
insects helping. However, it would be very hard to know this if you don't write down all your
observations.
Create the Final Presentation
There are several essential elements to a good presentation:
1. Present your data using averages, not just individual measurements. Also, don't present
the data more than once. For example, don't make a line graph and a pie chart of the same
data. Finally, don't include more than one variable on a graph.
2. Report your sample size (in the form n=sample size). Older students should do some
statistical analysis of their data such as standard deviation or a t-test.
3. Have print large enough to read from a distance.
4. Be sure that you understand all the terms and acronyms you display and/or use.
5. Think about future experiments and how you could expand on your project. Many students
do science fair projects for consecutive years. Judges also like to ask how you could change
the project for use in coming years. You should think about expanding and
significantly changing your project, not just repeating the same experiment next year.
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