19: Applications

Now that you (hopefully) understand how the chi-square test works, let’s use it to do some biology.
Here are 2 common applications – the mechanics are pretty much the same each time.

homozygous recessive mouse
The first application is in the area of genetics — it asks you to test whether the results of
mating fit the expectations for a dihybrid cross.

bee eater (bird)
The second application is in the area of ecology — it asks you to test whether a certain family of
birds has a preferred habitat.

magician in a red cape

At least two other applications of goodness of fit tests are also common in genetics — namely,
testing for linked gene crosses, and for Hardy-Weinberg equilibrium.

However, we will put off considering these situations until you’ve actually had a chance to read
about them in your textbook. But rest assured, chi-square will rear its, ahem, handsome head in later modules!