Statistics
How to Calculate Mean and Standard Deviation on TI-84 (1-Var Stats)
The TI-84's statistics engine computes mean, sum of squares, sample standard deviation (Sx), population standard deviation (σx) and quartiles (Q1, Med, Q3) with a single command.
Step-by-step
Open the List Data Editor
Press:STAT1: Edit...
Press the 'STAT' button in the third row, then press ENTER on '1: Edit...' to open lists L1 through L6.
Enter Your Numbers into List L1
Press:NumberENTER
Type each number in your dataset and press ENTER after each entry. To clear an old list, scroll up to highlight the header 'L1', press CLEAR and press ENTER.
Tip: NEVER press DEL on a list header (like L1), or you will delete the column! Use CLEAR.
Calculate 1-Variable Statistics
Press:STAT▶ (CALC)1: 1-Var Stats
Press 'STAT', use the Right Arrow key to switch to the 'CALC' menu and select '1: 1-Var Stats'.
Run the Computation
Press:CalculateENTER
Set List to 'L1' (FreqList blank for unweighted data), scroll down to 'Calculate' and press ENTER. Read 'Sx' for sample standard deviation or 'σx' for population standard deviation.
Weighted Statistics (Using Frequencies in List L2)
Press:FreqList: L2ENTER
If your data is formatted as values in L1 and their corresponding frequencies in L2, open '1-Var Stats', keep List as L1 and set FreqList to L2 by pressing [2nd] + [2]. Then scroll to Calculate and press ENTER.
Tip: Make sure L1 and L2 have the same number of rows, or you get ERR: DIM MISMATCH. This simulator has no wizard screen — type 1-Var Stats L1,L2 on the home screen instead.
EMERGENCY FIX: How to Restore Missing List L1
Press:STAT5: SetUpEditorENTER
If you accidentally pressed [DEL] on the L1 column header and list L1 vanished completely: press [STAT], scroll to '5: SetUpEditor' and press ENTER twice until it displays 'Done'. Reopen STAT Edit and all six standard columns (L1-L6) will be restored intact.
Tip: This is one of the most common panic moments in class, and no data is actually lost.
| TI-84 Symbol | Statistical Meaning | Formula Description | Application Context |
|---|---|---|---|
| x̄ (x-bar) | Sample / Population Mean | Σx / n | Average value of dataset |
| Σx | Sum of all observations | x₁ + x₂ + ... + xₙ | Intermediate calculation for variance & regressions |
| Σx² | Sum of squared observations | x₁² + x₂² + ... + xₙ² | Used in variance formulas and sum of squares |
| Sx | Sample Standard Deviation | √[ Σ(x - x̄)² / (n - 1) ] | REQUIRED for almost all school & AP Statistics problems |
| σx (sigma x) | Population Standard Deviation | √[ Σ(x - x̄)² / n ] | Used ONLY when dataset contains every member of population |
| n | Sample Size (Count) | Total number of data points entered | Verify no values were missed during data entry |
| minX | Minimum value | Lowest number in list | Boxplot lower whisker |
| Q1 | First Quartile (25th percentile) | Median of lower half of dataset | Boxplot left edge, IQR = Q3 - Q1 |
| Med | Median (50th percentile) | Middle number when data is sorted | Robust measure of central tendency |
| Q3 | Third Quartile (75th percentile) | Median of upper half of dataset | Boxplot right edge |
| maxX | Maximum value | Highest number in list | Boxplot upper whisker |
Common mistakes
- Using population standard deviation (σx) when homework or exams specify sample standard deviation (Sx).
- Leaving frequency list set to an old list with mismatched length, triggering ERR: DIM MISMATCH.
- Accidentally deleting list L1 with the DEL key instead of clearing it with CLEAR.
- Forgetting to check the 'n' count to verify that all data values were entered correctly.
Frequently asked questions
What is the difference between Sx and σx on TI-84?
Sx is the sample standard deviation (divides by n-1), used when your data represents a sample of a larger group. σx is population standard deviation (divides by n), used when you have the entire population.
HELP! I accidentally deleted list L1 from my calculator. How do I get it back?
Do not panic; your data is safe! Press [STAT], scroll down to option '5: SetUpEditor' and press ENTER. When the screen says 'Done', go back to [STAT] → 1: Edit... and your L1 column will be right where it belongs.
How do I find the correlation coefficient (r and r²) in linear regression?
Stat diagnostics are off by default. On OS 5.x press [MODE] and set STAT DIAGNOSTICS to ON. On any model you can instead press [2nd] + [0] (CATALOG), scroll to 'DiagnosticOn' and press ENTER twice until it says 'Done'. Then run [STAT] → CALC → 4: LinReg(ax+b) and both 'r' and 'r²' appear.
How do I clear an entire statistical list quickly?
Open [STAT] → 1: Edit..., use the Up Arrow to highlight the column header (e.g. L1), press [CLEAR] and press [ENTER]. All values in the list will instantly erase.