Examples of linear, quadratic, and cubic fitted lines

Minitab can fit three types of equations (lines) to your data:

· linear:	Y = b0 + b1 X
· quadratic:	Y = b0 + b1X + b2X $image\squared.gif$
· cubic:	Y = b0 + b1X + b2X $image\squared.gif$ + b3X $image\cubed.gif$

In each equation, Y is the value of the response variable, X is the value of the predictor variable, and b0, b1, b2, and b3 are constants.

Below are plots of data fitted with each type of equation.

Linear

$image\corr_1n.gif$

An example of data best fit with a linear equation. (The equation for the line shown is Y = -10.73 + 0.57X)

Quadratic

$image\corr_4n.gif$

An example of data best fit with a quadratic equation. (The equation for the line shown is Y = 51.03 - 2.82X + 0.05X $image\squared.gif$ )

Cubic

$image\fitt_6n.gif$

An example of data best fit with a cubic equation. (The equation for the line shown is Y = - 0.99 + 8.01X - 3.08X $image\squared.gif$ + 0.26X $image\cubed.gif$ ).

Related Charting Tools

Free online chart generators for statistical analysis:

Useful tools: