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Richardthughes



Posts: 10131
Joined: Jan. 2006

(Permalink) Posted: Mar. 11 2011,11:25   

Quote (Raevmo @ Mar. 11 2011,05:37)
Quote (Richardthughes @ Mar. 10 2011,11:59)
for a freind, actually:

"Iíve got one population that is a sub-set of another. I know the counts in both, the means and the standard deviations. What stat test can I use to teel if the mean of the sub-set is statistically different from the known mean of the whole? I think a t-test assumes two independent sets of data which these are not."

Halp!

If the mean (say mu) of the total population is known (say mu=mu_0), and the "counts" in the total population are normally distributed (the word "counts" actually suggests that the data are count data. i.e. non-negative integers, rather than continuous normal data), then a one-sample t-test could be used to test whether the sample is from a population with mu=mu_0.

Alternatively, take bootstrap samples from the sample and see how far out †mu_0 is in the bootstrap distribution of the mean.

Just to clarift above - counts are the population sizes. Oh pivot tables, you harsh mistress!

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