For a given data set, standard deviation measures how spread out the numbers are from an average value. This measurement of average variance has a prominent place in many fields related to statistics, ...

Brian Beers is a digital editor, writer, Emmy-nominated producer, and content expert with 15+ years of experience writing about corporate finance & accounting, fundamental analysis, and investing.

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 ...