[R] Pearson's Chi-squared Test
Jorge Magalhães
jmagalhaes at oninetspeed.pt
Sat Apr 12 12:48:04 CEST 2003
How i can perform a Pearson's Chi-squared Test in this data set:
| Outcome
-----------------+-----------+----------------------------------+
Treatment | Sex | None |Some | Marked | Total
-----------------+------------+--------+--------+-------------+
Active | Female | 6 | 5 | 16 | 27
| Male | 7 | 2 | 5 | 14
----------------+-------------+--------+--------+-------------+
Placebo | Female | 19 | 7 | 6 | 32
| Male | 10 | 0 | 1 | 11
---------------+-------------+---------+--------+-------------+
Total 42 14 28 84
if i do:
y<- matrix(c(5,6,16, 19,7,6,7,2,5,10,0,1), nc=3)
and
chisq.test(y) i found that X-squared=20.3176 but the true value is 15.075
(http://www.math.yorku.ca/SCS/Courses/grcat/grc2.html#H2_43:Sample)
Now i tried:
the Cochran-Mantel-Haenszel Chi-Squared Test for Count Data:
x <- array(c(6, 19, 7, 10,
5, 7, 2, 0,
16, 6, 5, 1),
dim = c(2, 2, 3),
dimnames = list(
Active = c("Female", "Male"),
Placebo = c("Female", "Male"),
Outcome.Level = c("None", "Some", "Marked")))
mantelhaen.test(x)
and now X-squared=2.0863
What is wrong?
Best regards
Many thanks in advance
Jorge M.
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