Dawnbridge

TI-84 Plus CE field manual for IB Math

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23

Linear regression and r

All courses

Enter paired data into two table columns, enable the calculator's correlation diagnostics, run linear regression, and read the regression equation and r.

Goal

Find the least-squares regression line and correlation coefficient for ​(1,2.1),  ​(2,2.9),  ​(3,3.7),  ​(4,4.6),  ​(5,5.1).

1

Check the stat diagnostic is on so ​r​ shows (Skill 3).

2

Open the list editor with → 1: Edit. Enter x-values in L1 and y-values in L2.

NORMALFLOATAUTOREALRADIANMP
L1L2L3L4L512.1------------------22.933.744.655.1------------
3

Run linear regression: press , move to CALC, choose LinReg(ax+b), set Xlist = L1 (type L1 with ) and Ylist = L2 ( ), then choose Calculate.

NORMALFLOATAUTOREALRADIANMP
LinReg(ax+b)
Xlist:L1
Ylist:L2
FreqList:
Store RegEQ:
Calculate
4

Look at the data too. Press , turn Plot1 on, then for ZoomStat. A high ​r​ on plainly curved data still means the wrong model.

Result

The regression line is ​y≈1.37+0.77x, and the correlation coefficient is ​r≈0.997.

Your turn

Work each one on your calculator, then check the answer.

  1. 1

    Find the regression line and ​r​ for ​(1,3.8),  ​(2,5.1),  ​(3,6.4),  ​(4,8.2),  ​(5,9.3),  ​(6,10.9).

  2. 2

    Find the regression line and ​r​ for ​(1,9.2),  ​(2,7.9),  ​(3,6.1),  ​(4,4.8),  ​(5,3.5).

  3. 3

    Find the regression line and ​r​ for ​(2,3.1),  ​(4,4.9),  ​(6,7.2),  ​(8,8.8),  ​(10,11.3).