Self Assessment Question # 3 for Lesson 11

by Dr Jamie Love © 2002 - 2010
Genetics Course

A fish biologist collects 70 female trout and 50 male trout from a river down steam of a chemical plant. She suspects that the plant is releasing a chemical that changes the sex ratio in the river. (Maybe the plant releases chemicals that kill males more than females or maybe it is releasing chemicals that cause males to become females! )

Calculate the chi square and use it to determine if the sex ratio of this trout population is "off" (or "skewed" as statisticians say). Hint : start by asking, "What would be the numbers of males and females if nothing was wrong?". You'll need this table, on the right, to come to a conclusion.

Degrees of Freedom 5 % Significance Levels 1 3.84 2 5.99 3 7.81 4 9.49

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