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Clyde, thank you very much for answering my question on prevalence and sample size.

I admit, it got me curious -- why ISN'T sample size important? There seems to be so much fuss about getting the right sample size.

Well, it

1. The error is generally

2. Because the error is roughly 1 / √(N), where N is the sample size, you can really do a fairly good job with a (relatively) small sample. 10,000 people, for example, is a very small sample when you consider a population of 5 million, 30 million, 1 billion, etc. Even in a small population, if you have 4000 people and you survey 500 of them your figures are good within 4% (and 4% of that population is only 160 people, which isn't that bad relatively speaking).

I can answer all questions up to, and including, graduate level mathematics. I do not have expertise in statistics (I can answer questions about the mathematical foundations of statistics). I am very much proficient in probability. I am not inclined to answer questions that appear to be homework, nor questions that are not meaningful or advanced in any way.

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