Six Sigma is a data-driven approach to quality, aimed at reducing variation and the associated defects, wastes, and risks in any process. This article explores the basics of Six Sigma process quality ...

The normal distribution is the probability distribution that plots all of its values along a symmetrical bell curve, with the highest probabilities centered around the mean value and tapering out ...

In response to my article, Is the Stock Market Too Concentrated?, which relied upon standard-deviation calculations to assess investment risk, a reader wrote: “My problem [with your argument] is ...

Investopedia contributors come from a range of backgrounds, and over 25 years there have been thousands of expert writers and editors who have contributed. Andy Smith is a Certified Financial Planner ...