How to Find Standard Deviation on a TI-84

Standard deviation measures how spread out a data set is around its mean — a small value means the data clusters tightly, a large one means it’s scattered. A TI-84 computes it for you via 1-Var Stats, but it reports two numbers, not one, and picking the wrong one is the most common mistake.

Two standard deviations, one data set

Sx is the sample standard deviation, dividing by n - 1. Use this whenever your data is a sample drawn from a larger population — which is almost always the case in a statistics class or a real experiment.

σx is the population standard deviation, dividing by n. Use this only when your data genuinely is the entire population, not a sample of it — for example, the test scores of every student in one specific class, if that class itself is what you’re studying.

The two will always differ slightly, with σx coming out smaller. If a problem doesn’t specify which one it wants, “sample” (Sx) is the safer default.

Entering the data

On the physical calculator, this is STAT → EDIT to type values into a list (usually L1), then STAT → CALC → 1-Var Stats L1, which returns the mean (x̄), both standard deviations, sample size (n), and more in one output.

Try it yourself

Go to Tools → Lists & Stats on the TI-84 Calculator, paste your comma-separated values into any list, select it, and press 1-Var Stats. The result includes both Sx and σx side by side, so there’s no need to remember a separate formula for each.