Goodness-of-fit test

A goodness-of-fit test evaluates whether an observed frequency distribution “fits” expected frequencies under a particular model.

 
 
Chi-square goodness-of-fit tests allow us to assess whether a sample of categorised observations differs from our expected values more than we would expect j...
 

Goodness-of-Fit Tests

Goodness-of-fit tests allow us to asses whether counts of observations in different categories differ from what we would expect based on a particular expectation about what the observed frequencies ought to be.

Additional Resources

Whitlock & Schluter - The Analysis of Biological Data

Chapter 8: pages 203-221 [Sapling]

 

Chi-squared goodness of fit test (video 1)

Intro: Worked example of a goodness-of-fit test.

 

Goodness of fit test in R

Intermediate: Code tutorial video in R.

Chi-squared goodness of fit test (video 2)

Intro: Example test with graphics and sound effects.

 

What are degrees of freedom?

Intermediate: Explanation of degrees of freedom in a Chi-squared test.

Review Questions

 

  1. What type of data do you need for a chi-square test?

  2. What is the purpose of a goodness-of-fit test?

  3. How many cases need to appear in one category for chi-square?

The Next Steps

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