Richardthughes
Posts: 10613 Joined: Jan. 2006

Quote (Raevmo @ Mar. 11 2011,05:37)  Quote (Richardthughes @ Mar. 10 2011,11:59)  for a freind, actually:
"I’ve got one population that is a subset 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 subset is statistically different from the known mean of the whole? I think a ttest 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. nonnegative integers, rather than continuous normal data), then a onesample ttest 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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