The chi-squared test

... The chi-squared test Problem: Mendel's Law of Independent Assortment makes a prediction about the ratios in which phenotypes occur. If we observe a population it is possible that we observe different results than those we can predict with the help of Mendel's laws. Example: Garden peas We calculate/predict the phenotypic ratio of garden peas: Y= yellow y = green R = round r = wrinkled First of all we create a test cross to predict the genotypes/phenotypes if the genotype of the F1 is YyRy: YR Yr yR yr YR YYRR YYRr YyRR YyRr Yr YYrR YYrr YyrR Yyrr yR yYRR yYRr yyRR YyRr yr YyRr Yyrr yyRr yyrr Ratio: 9 (round yellow) : 3 (round green) : 3 (wrinkled yellow) : 1 (wrinkled green) Genotypes: Not interesting for our topic If we observe 556 peas, then, according to the calculated ratio, they should be characterised as follows: # round yellow 312.75 why? 556 / 16 * 9 # round green 104.25 why? 556 / 16 * 3 # wrinkled yellow 104.25 why? 556 / 16 * 3 # wrinkled green 34.75 why? 556 / 16 * 1 The calculated values are called E =

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