Texas Instruments TINSPIRECX manual Charts with Two Variables, Fitting a Line by Hand and Eye

Charts with Two Variables

Create a new Data & Statistics page.

Notice both axes are marked Click to add variable.

As before select mshoe for the horizontal axis.

Move the cursor to the left edge of the screen, click x and select the variable mhand for the vertical axis.

This displays the scatterplot.

First Steps with TI-Nspire™

Tutorial 7: One- and two-variable statistics

Ready to add a 2nd variable

It may be that there is a positive correlation and a relationship between hand span and shoe size, so it may be appropriate to model this relationship with a linear function. The Analyze menu provides a range of tools to use.

Fitting a Line by Hand and Eye

First try adding a line of best fit by eye, using option

2:Add Movable Line. This displays a straight line together with a functional relationship between mshoe and mhand. The line can be dragged into a best-fit position using the two cursors for rotate and translate, in exactly the same way as a straight line can be moved manually in the Graphs and Geometry applications.

Translating the line

Powerful options in the Analyse menu

Rotating the line

Move to the middle of the line to get the translate cursor. Click and hold x to grab it. Now move the line into position. Click again x to release the cursor.

Move towards one end of the line to show the rotate cursor. Click and hold x to grab it. Use the Touchpad to rotate the line.

Click again x to release the cursor.

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