In 1936, statistician and geneticist R.A. Fisher reanalyzed Mendel's famous pea data and, using the Chi-square statistic, determined that Mendel had faked his data. Chi-square is a 'goodness of fit' test that determines whether your observed data are different from the expected data. Fisher determined that there was a 7 in 100,000 chance of Mendel obtaining the data that he reported. Some say that Mendel 'massaged' his data by stopping counting when he arrived at the right numbers, others say that he failed to report numbers that did not support his hypotheses. Still others say he must have just been lucky- like a monk would lie! Does it matter? Mendel remains highly respected today because, whether or not he faked his data, his hypothesis was right on. Below are some of Mendel's original monohybrid cross data. Perform your own Chi-square analyses as requested below, testing whether the observed data are different than those expected.
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Results of Mendel's monohybrid crosses
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Parental Phenotypes
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F1 phenotype
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F2 phenotype
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Round x Wrinkled
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All Round
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5474 round, 1850 wrinkled
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Yellow x Green
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All Yellow
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6022 yellow, 2001 green
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Purple x White
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All Purple
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705 purple, 224 white
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Axial x Terminal
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All Axial
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651 axial, 207 terminal
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Long x Short
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All Long
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787 long, 277 short
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1) What is the expected value for the recessive phentotype of the cross Long versus Short?
2) What is the Chi Square Sum (rounding to 3 significant figures) for Long versus Short cross?
3) What is the P-value (rounding to 3 significant figures) for Long versus Short cross?
4) What is the expected value for the recessive phentotype of the cross Round versus Wrinkled?
5) What is the Chi Square Sum (rounding to 3 significant figures) for Round versus Wrinkled cross?
6) What is the ChiSquare value for the recessive phentotype of the cross Yellow versus Green?
7) What is the Chi Square Sum (rounding to 3 significant figures) for Yellow versus Green cross.
8) What is the expected value for the recessive phentotype of the cross Purple versus White.
9) What is the Chi Square Sum (rounding to 3 significant figures) for Purple versus White cross?
10) What is the expected value for the recessive phentotype of the cross Axial versus Terminal?
11) What is the Chi Square Sum (rounding to 3 significant figures) for Axial versus Terminal cross?