Simple question about certainty/confidence in astronomy

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SUMMARY

The discussion centers on the interpretation of "3-sigma confidence" in the context of WMAP data suggesting a lower limit on reionization at z > 6.7. A 3-sigma confidence level indicates that if the true value is 6.7, approximately 1 in 400 measurements would yield results as extreme as the observed data. This statistical measure is crucial for understanding the reliability of astronomical data and the significance of findings in cosmology.

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  • Basic knowledge of cosmological concepts such as reionization
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cepheid
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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:

https://www.physicsforums.com/showthread.php?t=261118

Based on the responses there, I still don't quite understand what this sigma business is all about.
 
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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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