[R] small sample size confidence interval by bootstrap
jwd at surewest.net
Sat Apr 1 22:00:14 CEST 2006
On Friday 31 March 2006 18:21, Urania Sun wrote:
> Hi, All:
> I only have 4 samples. I wish to get a confidence interval around the mean.
> Is it reasonable? If not, is there a way to compute a confidence interval
> for such small sample size's mean?
> Many thanks,
With a sample that small, it is far safer to simply consider them as four
examples and leave it at that. In a population where there is little
variation (say an archaeological projectile point type with a nech width that
varies between 3 and 5 mm), the examples are likely to be close to typical,
and the difference isn't really llikely to be important anyway. However, in
a population with considerable variation (for example height in humans) you
can see that trying to make any generalizations from 4 examples is going to
be more likely to be misleading than anything else.
If your sample of four is your entire population, you have all the information
possible through simple measurements. But, if the population were 100 the
number of possible samples of size 4 is, as Gnumeric assures me, about 4 x
10^306, which, to put it scientifically, is a whole bunch. It'is better not
to generalize from small samples.
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