# [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