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The $2.00 science fair project

Posted by on January 16, 2012

For less than 2 dollars (plus some kitchen items) you can complete an A+ science fair experiment

Short on time and money, but still need to do a science fair project?

Then this idea is for you and FYI it also works as a math fair project.

It is unique (i.e., I made it up), cheap, easy, and follows the scientific method.


Step 1 Research/Question: Ecologists study communities of organisms including plants, animals, fungi, protists, and bacteria. Since it is impossible to monitor every individual, they need to take samples to gain information on each population. Scientists have to make a decision on how big of a sample to take given limits on time, labor, and resources. Sample size might affect how accurate and/or how precise their final findings are.

Do some research on accuracy vs. precision and find the classic bull’s-eye drawings to learn the difference between the concepts.

Question: What is the effect of sampling size on accuracy and precision?

Step 2: Write your hypothesis:

As sampling size increases, accuracy will (increase/decrease/stay the same) and precision will (increase/decrease/stay the same), because …

Step 3: Experiment

• 1 lb bag of dry black beans ($0.89)
• 1 lb bag of dry white beans ($0.89)
• A container you can not see through (brown paper bag, shoe box, old gift bag, or metal bowl)
• A set of measuring cups (minimum: ¼, ½ , 1 cup)

Make a simple ecosystem by putting 500 black beans & 500 white beans into the container, and mixing well.

1. Without looking, scoop out a “sample” with the ¼ measuring cup
2. Count the number of each color bean
3. Calculate the ratio of black to white beans
4. Put all the beans back into the container, repeat steps 1-4, 2 more times
5. Change the sampling size by using ½ measuring cup
6. Repeat steps 1-5 for each measuring cup available

Step 4: Analyze Results

Make a bar graph with the sampling size on the x-axis and the ratio of black to white beans on the y-axis. Add a line to show where the “true value” (i.e. the 1:1 ratio you have in your simple ecosystem) is.

Step 5: Make a Conclusion
Does the sampling size affect accuracy (how close the sample is to the true value of a ratio of 1:1) and precision (how repeatable the results are for each measuring cup).


How does biodiversity affect accuracy and precision (hint: keep the sampling size the same but vary the number of different types of beans – black, white, red, green, brown, black-eyed, speckled, etc.)

3 Responses to The $2.00 science fair project

  1. Karla

    Have you ever thought about writing an e-book or guest authoring on other websites? I have a blog based upon on the same subjects you discuss and would really like to have you share some stories/information. I know my viewers would enjoy your work. If you are even remotely interested, feel free to send me an e mail.

  2. Aliza

    What would you title this science fair project? We’ll be doing it tonight! Due tmrw!!! Tysm!!! My son loves the idea!!!

    • Dr. Maille Lyons

      If you use just black and white beans, you could simply use a form of the question. So the title would be: The effect of sampling size on sample accuracy and precision.

      If you use several different colored beans, then you could use that question: Title: The effect of biodiversity on sampling accuracy and precision.

      Or you could brainstorm titles that are less “scientific” and more “fun” like: Bean Counting Bonanza

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