No, all is fine, for this one-sided test, you want to calculate the
upper part of the confidence interval. If it is less than zero you have
shown that the alternative is probably right -> the true value is below
the upper confidence interval boarder with probability 1-\alpha.
Uwe Ligges
On 14.01.2011 17:21, Ingo wrote:
Dear R,
I am using this R version:R version 2.11.1 (2010-05-31)(Cran Mirror Berlin)
It seems to me, that R constructs a wrong confidence intervall if you try to
get a one sided t-test.
If the true mean is 1 and my alternative hypothesis (H1) says that mu is smaller
("less")than zero the conf. intervall should reach +∞ and not -∞ if it is
constructed for the H0 saying that mu is greater or equal to zero.
rnorm(20,1)->n
mean(n)
[1] 1.206958
t.test(n,mu=0,alternative="less")
One Sample t-test
data: n
t = 9.3976, df = 19, p-value = 1 alternative hypothesis: true mean is
less than 0
95 percent confidence interval:
-Inf 1.429035 sample estimates:
mean of x
1.206958
Hope I am right you can help me if I am wrong.
Greetings,
Ingo Meemken
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