There is no such thing as an unpaired t-test. A t-test can be a paired,
one sample or two sample t-test. Since you want to compare the sample
against a given mean, you need a one sample t-test. You tried to do a
two sample test. That didn't work because you need at least two
observations in each group.
x <- c(23,25,29,27,30,30)
t.test(x[-1], mu = x[1])
One Sample t-test
data: x[-1]
t = 5.3634, df = 4, p-value = 0.005833
alternative hypothesis: true mean is not equal to 23
95 percent confidence interval:
25.50814 30.89186
sample estimates:
mean of x
28.2
Cheers,
Thierry
------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Reseach Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
[EMAIL PROTECTED]
www.inbo.be
Do not put your faith in what statistics say until you have carefully
considered what they do not say. ~William W. Watt
A statistical analysis, properly conducted, is a delicate dissection of
uncertainties, a surgery of suppositions. ~M.J.Moroney
-----Oorspronkelijk bericht-----
Van: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Namens Robin Hankin
Verzonden: donderdag 23 november 2006 14:12
Aan: [EMAIL PROTECTED]
Onderwerp: [R] t.test()
Hi
I have a vector x of length n. I am interested in x[1]
being different from the other observations (ie x[-1]).
My null hypothesis is that x[1]
is drawn from a Gaussian distribution of the same
mean as observations x[-1], which are assumed
to be iid Gaussian. The (unknown) variance
of x[1] is assumed to be the same as the
variance of x[-1].
This should be an unpaired t-test.
But
> x <- c(23,25,29,27,30,30)
> t.test(x=x[1] , y=x[-1])
Error in t.test.default(x = x[1], y = x[-1]) :
not enough 'x' observations
>
What arguments do I need to send to t.test() to test my null?
--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
tel 023-8059-7743
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