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Simple question about certainty/confidence in astronomy

  1. Oct 4, 2008 #1


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    In this statement:

    "[WMAP data suggest] a lower limit on reionization of z > 6.7 with 3[itex]\sigma[/itex] confidence."

    What is the meaning the of the 3-sigma part in this context? See also my other thread here:


    Based on the responses there, I still don't quite understand what this sigma business is all about.
  2. jcsd
  3. Oct 4, 2008 #2

    Vanadium 50

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    What they mean is if the true value were 6.7, and you performed a large number of different measurements, one would expect about 1 in 400 of them to fluctuate to a result at least as extreme as what was measured.
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