Table of Contents

• Prequiz...
• 1: Do those shoes fit?
• 2: Dilbert's 3 day work week
• 3: The day is saved . or not
• 4: The Brute Force method
• 5: Computer = brute force
• 6: What's your threshold for pain?
• 7: Sick-day sistribution
• 8: A brief recap of the Brute Force Method
• 9: The Brute Force method again
• 10: Using arithmetic instead of Brute Force
• 11: One small correction
• 12: How big is big?
• 13: Degrees of Freedom
• 14: The magic lookup table
• 15: The answer, finally
• 16: Summary of chi-square
• 17: Another example for chi-square
• 18: So, which method do you like better?
• 19: Applications
• 20: Example 1: Testing for a dihybrid ratio
• 21: Example 2: Habitat selection (ecology)
• 22: Review and Words of Wisdom

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.

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.

The second application is in the area of ecology -- it asks you to test whether a certain family of birds has a preferred habitat.

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!