How to find Pearson's r and Spearman's rank correlation on the Casio fx-CG50, TI-84 Plus CE and TI-Nspire CX II

On the fx-CG50: MENU → 2 (STATISTICS) → F2 (CALC) → F3 (REG) → F1 (X) → F1 (ax+b).On the TI-84 Plus CE: stat → CALC → 4: LinReg(ax+b).On the TI-Nspire CX II: menu → Statistics → Stat Calculations → Linear Regression.

Pearson's product-moment correlation coefficient and Spearman's rank coefficient (by ranking, then r). Exact keystrokes for the fx-CG50 first, then the other calculators, a worked example you can check your answers against, the mistakes that cost marks, and the same thing in Desmos.

Calculators: Casio fx-CG50 (OS 3.80) · TI-84 Plus CE (OS 5.8.x) · TI-Nspire CX II (OS 6.x). Checked September 2026.

When you need it

Pearson's r in AA and AI; Spearman's r_s in AI (SL and HL) when the relationship is monotonic but not linear, or the data are ranks. No GDC has a Spearman button: rank the data, then find r of the ranks.

Practise it: SL AI bivariate data · SL AI correlation and regression · SL AA bivariate data.

Which IB course and paper

Course	GDC papers	What you use it for
AA SL	Paper 2 (Paper 1 is calculator-free)	Pearson's r (Spearman's rank is not in AA).
AA HL	Papers 2 and 3 (Paper 1 is calculator-free)	As SL.
AI SL	Papers 1 and 2	Pearson's r and Spearman's rank correlation coefficient.
AI HL	Papers 1, 2 and 3	As SL.

A GDC is allowed on every AI paper and on AA Papers 2 and 3; AA Paper 1 is calculator-free, so learn the method by hand as well.

Topic notes: Correlation, regression, and Pearson's r (AI SL) · Linear regression and residual analysis (AI HL).

Keystrokes on your calculator

Pick your calculator: the page remembers it next time.

Correlation r and Spearman's rank on the Casio fx-CG50

Written for OS 3.80 (menus unchanged from OS 3.60 onwards as far as we can tell). Casio fx-CG50: graphic (GDC).

Key sequence, from the steps below.

Watch the key presses on the fx-CG5016 presses, one at a time

The walkthrough needs JavaScript. The same key presses are in the numbered steps below.

Watch every key press on YouTube: the fx-CG50 playlist

MENU 2 (STATISTICS). Type the x values into List 1 and the y values into List 2, pressing EXE after each. (Clear an old list first: highlight the list, F6 (▷) F4 (DELETE-ALL) F1 (Yes).)
Pearson's r: F2 (CALC) F3 (REG) F1 (X) F1 (ax+b). Read r.
Spearman: type the ranks of x into List 3 and the ranks of y into List 4 (rank each list separately, smallest = 1; tied values share the mean rank).
F2 (CALC) F6 (SET): XList = List3, YList = List4, EXIT, then F3 (REG) F1 F1 again. This r is r_s.

Schematic Casio fx-CG50 screen for correlation r and spearman's rank: the LinearReg(ax+b) screen showing a =…, b =…, r =0.95549212, with COPY, DRAW on the F-keys — Schematic fx-CG50 screen (our drawing, not a photo); the bottom row is what F1–F6 do here.

Sorting helps you rank: F1 (TOOL) → SORT-ASC in the list editor, but sort a copy, not your original lists, or the x–y pairs break.
Set the SET menu back to List1/List2 afterwards.

For teachers: Show on the board Print a keystroke card Teaching GDC skills

Worked example

x: 12, 15, 17, 20, 23, 25, 28, 30. y: 40, 44, 43, 52, 55, 51, 60, 63. Find r and Spearman's r_s.

Answers (checked with Python)

r = 0.955492. Ranks of x: 1–8; ranks of y: 1, 3, 2, 5, 6, 4, 7, 8. r of the ranks gives r_s = 0.905.

Try it: correlation and regression calculator (free, shows the working)

Now try it on an exam-style question

Use the keystrokes above on IB-style correlation and regression questions. Free to try, no sign-up.

Try a correlation and regression question

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Common calculator mistakes

Ranking the two lists together instead of separately.
Ties: two equal values in 3rd and 4th place both get rank 3.5, and the next value gets 5.
Reordering one list only (sorting x without its y) destroys the pairs.
Reading r² as r: r = 0.955 but r² = 0.913.
Interpreting: r close to 1 means a strong positive linear relationship, not that x causes y.
Accuracy: unless the question says otherwise, IB markschemes want answers exact or to 3 significant figures. Keep the full calculator value for later parts and round only the answer you write down (x = 2.094551… is written 2.09, not 2.1 or 2.0946).

If you get an error

fx-CG50: Ma ERROR

Ma ERROR Casio's Math ERROR: the result is outside the allowable calculation range, or you are trying to do an illegal mathematical operation, such as dividing by zero. Check: Look for a zero denominator, sin⁻¹ or cos⁻¹ of a number bigger than 1 (often a wrong side or angle in the sine or cosine rule), the log of 0 or of a negative number, and a value stored in a variable earlier that you forgot about. Fix: Casio's advice: check your input values and change them so the result is within the allowable range.

TI-84 Plus CE: ERR:DOMAIN, ERR:DIM MISMATCH, ERR:INVALID DIM, ERR:SYNTAX, ERR:STAT

ERR:DOMAIN A value given to a function or instruction is outside the values it accepts. In a regression, TI says it means the data do not suit the model you chose. Check: Is every input allowed? σ must be positive, p between 0 and 1, and sin⁻¹ or cos⁻¹ needs a number from −1 to 1. Exponential and power models need positive data. Fix: Change the value that is out of range, or choose a model that suits the data.

ERR:DIM MISMATCH Lists or matrices in the same operation have different sizes (TI's example: multiplying two lists with different numbers of elements). Check: L1 and L2 with different numbers of values (one value missed or typed twice), a frequency list of the wrong length, or matrices whose sizes cannot be multiplied. Fix: Make the lists the same length, or check the size of each matrix.

ERR:INVALID DIM TI's knowledge base: one or more stat plots are turned on, but the lists they use are empty. Check: A stat plot left on from a statistics question, so the error appears when you graph a function. Fix: Turn off the stat plots you are not using, or put the data back in the lists.

ERR:SYNTAX The command contains a syntax error: a misplaced function, argument, bracket or comma. Check: TI points out that subtract − and negative (−) are different keys, and using the wrong one causes this error. Then check the brackets and commas. Fix: Find the misplaced function, argument, bracket or comma and correct it.

ERR:STAT A statistics calculation was tried on lists that are not suitable. A statistical analysis needs at least two data points. Check: An empty or one-value list, or the wrong list named in the command. Fix: Check the lists named in the command and the data in them.

TI-Nspire CX II: Domain error, Dimension mismatch, Syntax error

Domain error An argument must be in a specified domain, and this one is not (TI's example: rand(0)). Check: Is every input allowed? σ must be positive, p between 0 and 1, and sin⁻¹ or cos⁻¹ needs a number from −1 to 1. Fix: Change the value that is out of range.

Dimension mismatch Two or more arguments must have the same dimension and do not (TI's example: [1,2]+[1,2,3]). Check: Lists of different lengths in a statistics command, or vectors or matrices of different sizes. Fix: Make the lists, vectors or matrices the sizes the operation needs.

Syntax error The syntax checker found a problem. Check: A missing bracket or comma. Fix: Correct the expression and try again.

Every error message explained, calculator by calculator →

Do it in Desmos

Not in the exam. Desmos is not an approved calculator for IB exams, so never rely on it for Paper 2. It is excellent for learning, checking a GDC answer and building graphs for your Internal Assessment (IA).

Make lists X = [12, 15, …] and Y = [40, 44, …].
corr(X, Y) gives Pearson's r; spearman(X, Y) gives Spearman's r_s directly (Desmos ranks and handles ties for you).
Plot (X, Y) to see the scatter diagram.

Open desmos.com/calculator (free, in any browser) and type:

X=[12,15,17,20,23,25,28,30]
Y=[40,44,43,52,55,51,60,63]
(X,Y)
corr(X,Y)
spearman(X,Y)

Questions

Can I use a calculator for correlation r and Spearman's rank in the exam?

In IB Maths you can use one approved GDC on every AI paper and on AA Papers 2 and 3, in exam mode. AA Paper 1 is calculator-free, so learn the method by hand as well.

What are the fx-CG50 keystrokes for correlation r and Spearman's rank?

MENU 2 (STATISTICS). Type the x values into List 1 and the y values into List 2, pressing EXE after each. (Clear an old list first: highlight the list, F6 (▷) F4 (DELETE-ALL) F1 (Yes).). Then Pearson's r: F2 (CALC) F3 (REG) F1 (X) F1 (ax+b). Read r. Then Spearman: type the ranks of x into List 3 and the ranks of y into List 4 (rank each list separately, smallest = 1; tied values share the mean rank). The full steps and the other calculators are in the keystrokes section above.

Does this work on other calculators?

Yes. This page has keystrokes for the Casio fx-CG50, TI-84 Plus CE and TI-Nspire CX II. The worked example has the same answers on every model, so use it to check.

What should I write as working?

Write the maths, not the key presses: say what you are finding in normal notation (the equation, the probability statement or the integral), then the calculator's answer exact or to 3 significant figures unless the question says otherwise. Keep full accuracy in later parts.

More calculator skills

Sources

Casio fx-CG50 Software User's Guide, OS 3.70 (PDF) : Casio fx-CG50, OS 3.80 (menus unchanged from OS 3.60 onwards as far as we can tell).
TI-84 Plus CE guidebook (Texas Instruments) : TI-84 Plus CE, OS 5.8.x.
TI-Nspire CX II guidebooks (Texas Instruments) : TI-Nspire CX II, OS 6.x.
Desmos Help Center for the Desmos functions.

Menu names are taken from each manufacturer's manual for the models shown. Menus can move slightly between OS updates: if a screen looks different on yours, the manual for your version is the reference, and please tell us so we can update this page. A calculator with no tab here has no checked steps for this skill yet. Worked-example answers were recomputed independently in Python.