Basic Probability and Chi-Squared Tests


Margaret A. Bakewell and Patricia J. Wittkopp

This resource describes an inquiry-based, in-class exercise designed for students working in small groups. It is designed to review and enrich student understanding of probability, how probabilities of individual events can be combined to make predictions about more complex outcomes, and how observed data can be compared to a null model based on probabilities using a chi-squared test. These skills are used extensively for classical genetic analysis. Throughout the activity, peers and instructors guide students through the process of developing and solving problems using probabilities and chi-squared tests in small groups.

Genetics Concept(s) Addressed:

Transmission/patterns of inheritance: How can one deduce information about genes, alleles, and gene functions from analysis of genetic crosses and patterns of inheritance?
Core Competencies Addressed:

Students should be able to implement observational strategies to formulate a question.

Students should be able to generate testable hypotheses.

Students should be able to design an experiment using appropriate controls and appropriate sample sizes.

Students should be able to gather and evaluate experimental evidence, including qualitative and quantitative data.

Students should be able to apply statistical methods when analyzing their data, and use patterns to construct a model.


Introductory undergraduate; biology/genetics majors
Activity Type:

In-Class/Lecture Exercise
Activity Length:

50 minutes


Bakewell, Margaret A. and Wittkopp, Patricia J. (2013). Basic Probability and Chi-Squared Tests. Genetics Society of America Peer-Reviewed Education Portal (GSA PREP): 2013.005; doi: 10.1534/gsaprep.2013.005

Resource Justification and Instructor Guide (PDF, Word)
Student Handout (PDF, Word)