In my lab I measure some chemical data. Output from the software I use contain also some stats, like the mean value, standard deviation and some number called SIGMA MEAN. My typical dataset looks like this: sample MgO Al2O3 a 5,307872109 7,45113642 b 8,496074587 9,182072932 c 1,413995015 7,488017765 d 5,241196501 12,15347965 e 1,592772949 7,863316958 f 0,518347063 4,050451192 g 1,117824945 5,952661741 Mean value: 3,384011881 7,734448094 Sigma: 2,992231593 2,53402361 Sigma mean: 1,130957237 0,957770898 I know what is mean value and standard deviation sigma, but I never heard about sigma mean. It is always smaller than sigma and it seems to depend on sigma. Please do somebody know what it is Sigma mean?