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Chapter26

# Chapter26 - Chapter 26 Comparing Counts Example#3 on p 712...

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Chapter 26 Comparing Counts

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Example #3 on p. 712 After getting trounced by your little brother in a children’s game, you suspect the die he gave to roll may be unfair. To check, you roll it 60 times, recording the number of times each face appears. Do these results (Data on the next slide) cast doubt on the die’s fairness?
(cont.) Face Count 1 11 2 7 3 9 4 15 5 12 6 6

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Goodness-of-Fit If the faces were distributed uniformly on each roll, we would expect about 1/6 of them to occur under each face. That suggests 60/6 = 10. How closely do the observed number of faces per roll fit this simple “null” model? A hypothesis test to address this question is called a goodness-of-fit.
Test Statistic The test statistic, called the chi-square statistic, is found by adding up the sum of the squares of the deviations between the observed and expected counts divided by the expected counts: - = expected expected) (observed 2 2 χ

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Chapter26 - Chapter 26 Comparing Counts Example#3 on p 712...

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