Your standard deviation doesn't match what your teammate's tool reports

I calculated the standard deviation two different ways and got two different numbers, and I don't know which one is right.

BeginnerRead 3 minDoing: twenty minutes6 steps

▶ Start

What you'll have at the end

One standard deviation, calculated with the sample formula (n minus 1), that another tool would reproduce on the same numbers.

Before you start

You need

A column of numbers you've already summarized once, plus a second standard deviation for the same numbers that a teammate's tool reported and doesn't match yours.

Not covered

Deciding whether the spread itself is too big to trust the average; this only settles which formula produced the number.

Leans on

Descriptive Statistics Cheat SheetHas the sample and population variance formulas, and Bessel's correction, side by side.
Microsoft Excel Cheat SheetLists the paired sample and population standard-deviation functions.

6 steps

Checked 26 Aug 2026

Part of the Descriptive Statistics cookbook