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    Re: Standard Deviation Question
    From: Bill Morris
    Date: 2013 Jan 4, 19:30 -0800

    "...when should I be using stdDevPop and when should I be using stdDevSamp?"

    Not being a maths whiz either (nor a statistician)I would say that for small numbers you should use stdDecSamp. As a rule of thumb, I have always regarded a sample of less than 30 as being "small". As you have seen, using the stdDevPop function gives you a larger figure for the standard deviation.

    The difference is unimportant in large samples. For example in 60 estimations of index error , the SD pop was 0.228 and the SD sample was 0.226.

    I am inlcined to doubt the value of giving SDs for samples of n = 5. A sample size of n = 10 seems to be marginal; 20 would be more better. May we have a statistician's ruling?

    Bill Morris
    Pukenui
    New Zealand
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