AP Biology students complete Chi Square modeling

On Friday, April 20, students in Advanced Placement Biology learned how to use the Chi Square test by using M&M candies. The Chi Square test is often used in science to test if data you observe from an experiment is the same as the data that you would predict from the experiment.

Students were posed with the following scenario:

Have you ever wondered why the package of M&Ms you just bought never seems to have enough of your favorite color? Or, why is it that you always seem to get the package of mostly brown M&Ms? What’s going on at the Mars Company? Is the number of the different colors of M&Ms in a package really different from one package to the next, or does the mars Company do something to ensure that each package gets the correct number of each color of M&M? 

Students determined if the Mars Co. is true to its word by sampling a package of M&Ms and by doing a type of statistical test knows as a “goodness of fit” test. These type of statistical tests allow one to determine if any differences between observed measurements (counts of colors from our M&M sample) and expected (what the Mars Co. claims) are simply due to chance sample error, or if they happen some other reason. The Chi Square Analysis acted as a goodness of fit test for this experiment.

This type of test is usually performed with discrete data, using a table to determine the probability of getting a particular value. Students were able to chart their findings — and enjoy the M&Ms after the experiment’s conclusion!