Question

if some statistical data has a level of 5 sigma
what does this mean?

Answer 1

that it is 99.99999% accurate.

Answer 2

is like saying the z-score of all data was less than 5?

Answer 3

say a measurement give x= 125.3 with an accuracy level of 4.9 sigma."
so this means
the number is between 125.29999 < x < 125.300001
?

Answer 4

something like that?

Answer 5

Pretty much....for the Higgs stuff that's being announced right now it's something like 3x10^-7 of a percent.

Answer 6

One definition of 5 sigma is that the data is 10 standard deviations inside specification.
At plus and minus 5 sigma 99.999943% is inside specification.
Also at plus and minus 5 sigma a 1.5 sigma shift in the mean will reduce the percentage inside specification to 99.97673%