E-CodeHow to find a line of best fit on a TI-89 Titanium
In the Data/Matrix Editor, type the x values in c1 and the y values in c2, press F5 (Calc), ▶ and pick LinReg with x = c1 and y = c2, then ENTER. STAT VARS shows a and b for y = a·x + b: for 1, 2, 3, 4 and 3, 5, 7, 9 that is a = 2, b = 1.
Step by step
- Make a new data set. APPS 6 3 Press APPS, 6 for the Data/Matrix Editor, then 3 for New. The NEW box opens with Type set to Data.
- Name it d. ▼ ▼ , Press ▼ twice to reach Variable, then the , key: letters are on in this box, so it types d.
- Create it. ENTER ENTER Press ENTER twice: once to finish the name, once for OK. An empty table opens.
- Type the x values. 1 ENTER 2 ENTER 3 ENTER 4 ENTER Type 1, 2, 3 and 4 into column c1, pressing ENTER after each one.
- Go to the top of c2. ▶ ▲ ▲ ▲ ▲ Press ▶ to move to column c2, then ▲ four times to get back to its first row.
- Type the y values. 3 ENTER 5 ENTER 7 ENTER 9 ENTER Type 3, 5, 7 and 9 into c2, pressing ENTER after each one. Each y sits next to its x.
- Open Calc. F5 Press F5 for Calc. The Calculate box uses c1 for x and c2 for y. If a box is empty, type the column name.
- Open the types. ▶ Press ▶ to open the list of Calculation Types: OneVar, TwoVar and the regressions.
- Pick LinReg. ▼ ▼ ▼ ▼ ENTER Press ▼ four times to LinReg, the straight-line fit, then ENTER.
- Fit the line. ENTER Press ENTER for OK. STAT VARS opens with the line's numbers.
- Read the line. y = a·x + b with a = 2 and b = 1: the line is y = 2x + 1. corr = 1 means every point sits right on it.
What the screen shows
y = a·x + b with a = 2 and b = 1: the line is y = 2x + 1. corr = 1 means every point sits right on it.
Look for b=1. on the screen.
Try it with the keys lit up
This guide is one of E-Code's Learn lessons. Open it on E-Code's TI-89 calculator and each key lights up in turn as you press it.
Try “Find a line of best fit” on the TI-89 calculator
Related
Statistics programs for the TI-89 Titanium: