Contents

1 Cohran-Armitage test

library("DescTools")

tmp <- textConnection("
학년	흡연유무	학생수
1	무	38
2	무	43
3	무	33
1	유	6
2	유	7
3	유	15") 
df <- read.table(tmp, header=TRUE) 
close.connection(tmp)
head(df)


t1 <- xtabs(학생수 ~ 학년 + 흡연유무, data=df)
summary(t1)

CochranArmitageTest(t1, "increasing")
#CochranArmitageTest(t1)
#CochranArmitageTest(t1, "decreasing")

> summary(t1)
Call: xtabs(formula = 학생수 ~ 학년 + 흡연유무, data = df)
Number of cases in table: 142 
Number of factors: 2 
Test for independence of all factors:
	Chisq = 6.093, df = 2, p-value = 0.04752
> CochranArmitageTest(t1, "increasing")

	Cochran-Armitage test for trend

data:  t1
Z = -2.153, dim = 3, p-value = 0.01566
alternative hypothesis: increasing