Standard deviation is a metric that shows the variability of a security’s returns over time. It can be used to gauge volatility based on past performance and compare a future return to past returns.

When reviewing cash flow data for your small business, knowing the standard deviation can help you determine if the numbers are out of whack. Calculating standard deviation manually can be ...

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 ...