<a href="https://en.wikipedia.org/wiki/Normal_distribution" class="extiw" title="w:Normal distribution">Normal distribution</a> curve that illustrates <a href="https://en.wikipedia.org/wiki/Standard_deviation" class="extiw" title="w:Standard deviation">standard deviations</a>. Each band has 1 standard deviation, and the labels indicate the approximate proportion of area (note: these add up to 99.8%, and not 100% because of rounding for presentation.)
<a href="//commons.wikimedia.org/wiki/User:Mwtoews" title="User:Mwtoews">M. W. Toews</a>
CC BY 2.5
<span class="int-own-work" lang="en">Own work</span>, based (in concept) on figure by Jeremy Kemp, on 2005-02-09