michael Johnson thinks this is interesting: S is a symbol that means to sum or add up the things that follow it. From Hack #15. Identify Unexpected Outcomes from Statistics Hacks by Bruce Frey Publisher: O'Reilly Media, Inc. Released: May 2006 Note This should be "Sigma" and should be replaced by the actual symbol that looks sort of like a capital E in the above formula. Share this highlight http://www.safaribooksonline.com/a/statistics-hacks/447039/ Twitter Facebook Google Plus Email Get Instant Access Now Start a Free Trial Have an account? Sign in. Minimise Unlock the rest of Statistics Hacks and 30,000 other books and videos By clicking this box, you confirm that you have read and agree to the terms and conditions of our Membership Agreement, and you understand that when your trial period ends, you will be required to provide billing information if you wish to continue using the service. Unlock the rest of this book Start a Free 10-Day Trial loading Learn about Safari for Business Have an account? Sign in.