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Error propagation log base 2

  1. Jun 6, 2009 #1
    Hi,

    I am trying to represent my data in log2 form rather than "fold change" and I am embarrassed to say I can't remember how convert the error.

    For example, I have x=3.96 (mean), deltax=0.28 (standard dev).

    Thus, log2(x)=0.598.

    But how do I convert the error??

    I know how to do it for log10: 0.434(deltax/x) but I can't for the life of me remember how to derive it for an arbitrary base.

    Any help/pointers much appreciated.

    Thanks!
     
    Last edited: Jun 6, 2009
  2. jcsd
  3. Jun 6, 2009 #2
    Duh, figured it out.

    For y=ln(x), error dy=dx/x

    since lob(x) base b = ln(x)/ln(b)

    Then for y=lob(x) base b , error is dy=(1/ln(2))(deltax/x)

    Done. Cheers, -Alex
     
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