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Unformatted text preview: tics Introduction
TwoSample Test for Binomial Proportions
McNemar’s Test
Estimation of Sample Size and Power
R × C Contingency Tables
ChiSquare GoodnessofFit Test
The Kappa Statistic NormalTheory Method
Fisher’sExact Test YatesCorrected ChiSquare Test Cont’d...
ChiSquare distribution is a family of skewed distributions
indexed by the degrees of freedom.
In R, a 100 × u percentile of a chisquare distribution with d
degrees of freedom, denoted by χ2 ,u can be obtained by using
d
qchisq(u,d)
Probabilities (area under the curve) of a chisquare can be
obtained using the pchisq command.
Compute χ2,0.025 , χ2,0.975 , P (χ2 < 7) and P (χ2 > 10).
9
9
6
9
Returning to YatesCorrected ChiSquare test, we reject H0 if
2
X 2 > χ2,1−α and pvalue is P (χ2 > Xcomputed ).
1
1
This ChiSquare test is always a twosided test despite using
100(1 − α)th percentile of chisquare.
Chapter 10: Hypothesis Testing: Categorical Data Stat 491: Biostatistics Introduction
TwoSample Test for Binomial Proportions
McNemar’s Test
Estimation of Sample Size and Power
R × C Contingency Tables
ChiSquare GoodnessofFit Test
The Kappa Statistic NormalTheory Method
Fisher’sExact Test Fisher’sExact Test
This test is applicable when any of the expected frequencies is
less than 5.
Example: Suppose a retrospective study is done among men
ages 5054 in a speciﬁc county who died over a 1month
period. The investigators try to include approximately an
equal number of men who died from Cardiovascular disease
(the case) and men who died from other causes (the control).
Of 35 people who died from CVD, 5 were on highsalt diet
before they died, whereas of 25 people who died from other
cause 2 were on such a diet. Chapter 10: Hypothesis Testing: Categorical Data Stat 491: Biostatistics Introduction
TwoSample Test for Binomial Proportions
McNemar’s Test
Estimation of Sample Size and Power
R × C Contingency Tables
ChiSquare GoodnessofFit Test
The Kappa Statistic NormalTheory...
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 Fall '12
 SolomonHarrar
 Statistics, Biostatistics

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