How to Find Standard Deviation on the TI-84
Need the spread of your data fast? This standard deviation TI-84 guide shows you how to find standard deviation with 1-Var Stats: enter data in list L1, run STAT → CALC → 1-Var Stats, and read Sx for samples or σx for populations.
Quick answer: Press STAT, choose 1:Edit, and type your data into list L1. Then press STAT again, go to CALC, choose 1:1-Var Stats, and press ENTER twice. Scroll down: Sx is the sample standard deviation and σx is the population standard deviation. Use Sx for samples, σx for a full population.
Entering your data in list L1
Everything starts in the stat list editor. Your numbers need to live in a list before the calculator can analyze them.
- Press STAT and choose 1:Edit.
- If list L1 already has old numbers in it, highlight L1 at the top, press CLEAR, then ENTER to empty it.
- Type your first value, press ENTER, and repeat for every data point. Each entry lands in L1, one per row.
Double-check your entries against the original data — one typo here silently corrupts every statistic that follows. You can practice the whole workflow on our free TI-84 calculator in your browser.
Running 1-Var Stats
With data in L1, the calculation takes seconds — this is the core standard deviation TI-84 workflow:
- Press STAT and arrow right to the CALC tab.
- Choose 1:1-Var Stats and press ENTER.
- On the setup screen, make sure List shows L1 and FreqList is blank, then highlight Calculate and press ENTER.
The results screen shows a full summary: x̄ (mean), Σx (sum), Σx² (sum of squares), Sx, σx, and n (count). Arrow down to see the values below the first screen — Sx and σx are near the bottom.
Sx vs σx: which one do you need?
This is the question that trips up nearly every student, so here is the rule:
- Sx — sample standard deviation. Use it when your data is a sample drawn from a larger population (almost every class problem). It divides by n−1.
- σx — population standard deviation. Use it only when your data is the entire population — every member measured. It divides by n.
When a problem just says “find the standard deviation” without specifying, statistics classes almost always want Sx. If your answer is slightly off from the textbook, check whether you grabbed the wrong one — it is the most common mistake in this entire procedure.
Worked example
Find the standard deviation of the quiz scores: 72, 85, 90, 78, 88 — a classic standard deviation TI-84 exercise.
- STAT → 1:Edit → type the five scores into L1.
- STAT → CALC → 1:1-Var Stats → Calculate.
- Read the screen: x̄ = 82.6, n = 5, Sx ≈ 7.37, σx ≈ 6.59.
Since five quiz scores are a sample of the student’s overall performance, the answer is Sx ≈ 7.37.
Finding variance from standard deviation
Variance is simply the square of the standard deviation, and the TI-84 does not list it directly — but getting it takes one step. After running 1-Var Stats, press VARS → 5:Statistics → Sx (or σx), then press the x² key and ENTER. For the quiz-score example above, Sx² ≈ 54.3 is the sample variance. The theory behind variance and standard deviation is explained on Wikipedia’s standard deviation page.
Mistakes to avoid
- Old data in L1. Leftover numbers from a previous problem silently join your new data. Always clear L1 first.
- Reading σx instead of Sx. They sit right next to each other — slow down and pick the right one.
- Wrong list selected. If you entered data in L2, change the List field on the setup screen to match, or 1-Var Stats will analyze an empty L1 and throw ERR:INVALID DIM.
Standard deviation TI-84: frequently asked questions
Why do I get ERR:INVALID DIM running 1-Var Stats?
Usually the List field points to an empty list, or a stat plot is turned on with mismatched data.
What is the difference between Sx and σx on the TI-84?
Sx divides by n−1 (sample standard deviation); σx divides by n (population standard deviation). Use Sx unless you measured the entire population.
Can the TI-84 do standard deviation for grouped or frequency data?
Yes — enter values in L1 and their frequencies in L2, then set FreqList to L2 on the 1-Var Stats setup screen.
Where do I find variance?
The TI-84 does not list variance directly — square the standard deviation yourself: type Sx² on the home screen.
How do you find standard deviation on a TI-84?
Press STAT, choose 1:Edit, and type your data into list L1. Then press STAT again, go to the CALC tab, choose 1:1-Var Stats, and press ENTER twice. Scroll down the results screen to read Sx for samples or σx for a full population.
What is the difference between Sx and σx on a TI-84?
Sx is the sample standard deviation, used when your data is a sample drawn from a larger population (almost every class problem); it divides by n−1. σx is the population standard deviation, used only when your data is the entire population; it divides by n. When a problem does not specify, statistics classes almost always expect Sx.
How do you find variance on a TI-84?
The TI-84 does not list variance directly, because variance is simply the square of the standard deviation. On the home screen, recall Sx (or σx) via VARS → 5:Statistics, press the x² key, and press ENTER. For the quiz-score example, Sx² ≈ 54.3 is the sample variance.
What is 1-Var Stats on a TI-84?
1-Var Stats is the TI-84 routine that calculates one-variable statistics for the data in a list. With your data in L1, press STAT, arrow right to the CALC tab, choose 1:1-Var Stats, and press ENTER. The results screen shows a full summary: x̄ (mean), Σx (sum), Σx² (sum of squares), Sx, σx, and n (count).
