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    Re: Standard Deviation Question
    From: William Hawes
    Date: 2013 Jan 5, 12:53 -0800

    On 04 Jan 2013 at 21:00 Greg Rudzinski said:
    Here are 20 index error observations of Procyon using a Tamaya Jupiter with 7 x 35mm scope.
    0.2' 0.7'
    0.4' 0.7'
    0.4' 0.6'
    0.6' 0.4'
    0.8' 0.6'
    0.6' 0.7'
    0.7' 0.7'
    0.7' 0.4'
    0.7' 0.7'
    0.5' 0.4'
    n=20
    _
    x = 0.575'
    Sx = 0.1585'
    _________________________________________
    Greg, ran your data thru the TI-Nspire calculator. The results were

    stdDevSamp() > 0.1585 (agrees with your result)
    and
    stdDevPop() > 0.1545

    Frank (in his 02 Jan 2013 at 16:33 posting re: "Lunars and accuracy generally") used a Population StdDev and you used (above) a Sample StdDev.

    I guess I still have the same question. When should we be using Pop and when should we be using Samp? I'm starting to believe, from what has been said in other replies, that since one is using "all" the observed data then the Pop Std Dev is the most appropriate. Also, as others have said, it may not make a lot of difference since the difference only shows up in the third decimal place of an accurate to one decimal place set of data.

    FYI, I've pulled out my old college statistics book and have started plowing thru it from the beginning - as virtually all of it has long been forgotton.

    wmh
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