The document describes how to use a chi-square test to determine if observed offspring ratios from genetic crosses fit the expected ratios predicted by theories like Mendel's laws. It provides the chi-square formula and explains how to calculate expected values, degrees of freedom, and compare the calculated chi-square value to critical values in tables to determine if the observed ratios fit or reject the null hypothesis. An example using Mendel's pea plant data is shown to demonstrate applying the chi-square test.

11. Chi-Square Table

13. Another Example: from Mendel 556 1 556 total 34.75 1/16 32 wrinkled green 104.25 3/16 108 wrinkled yellow 104.25 3/16 101 round green 312.75 9/16 315 round yellow expected number expected proportion observed phenotype

17. Chi-Square Table

18. Mendel’s Yellow vs. Green Results