On Dec 3, 2012, at 1:40 PM, Troy S wrote:
Dear UseRs,
I'm running a chi-squared test where the expected matrix is the same
as the
observed, after rounding.
... after rounding you say?
R reports a X-squared of zero with a p value of
one. I can justify this because any other result will deviate at
least as
much from the expected because what we observe is the expected, after
rounding. But the formula for X-squared, sum (O-E)^2/E gives a
positive
value.
If O==E that sum would be identically 0 if the conditions stated
held ... which they do NOT for the case below.
What is the reason for X-Squared being zero in this case?
Troy
trial<-as.table(matrix(c(26,16,13,7),ncol=2))
x<-chisq.test(trial)
x
data: trial
X-squared = 0, df = 1, p-value = 1
x$expected
A B
A 26.41935 12.580645
B 15.58065 7.419355
x$statistic
X-squared
5.596653e-31
(x$observed-x$expected)^2/x$expected
A B
A 0.006656426 0.013978495
B 0.011286983 0.023702665
sum((x$observed-x$expected)^2/x$expected)
[1] 0.05562457
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