Defining a regression model

The Symbolic view includes an expression (Fit1 through Fit5) that defines the regression model, or “fit”, to use for the regression analysis of each two-variable data set.

 

There are three ways to select a regression model:

 

•

Accept the default option to fit the data to a straight

 

 

line.

 

 

•

Select one of the available fit options in Symbolic

 

 

Setup view.

 

 

•

Enter your own mathematical expression in Symbolic

 

 

view. This expression will be plotted, but it will not be

 

 

fitted to the data points.

 

Angle Setting

You can ignore the angle measurement mode unless your

 

Fit definition (in Symbolic view) involves a trigonometric

 

function. In this case, you should specify in the mode

 

screen whether the trigonometric units are to be

 

interpreted in degrees, radians, or grads.

To choose the fit

1.

In Numeric view, make sure

is set.

Fit models

2.Press SETUP-SYMBto display the Symbolic Setup view. Highlight the Fit number (S1FIT to S5FIT) you want to define.

3.Press and select from the list. Press when done. The regression formula for the fit is displayed in Symbolic view.

Eight fit models are available:

Fit model

Meaning

 

 

Lineair

(Default.) Fits the data to a straight

 

line, y = mx+b. Uses a least-squares

 

fit.

Logaritmisc

Fits to a logarithmic curve,

h

y = m lnx + b.

Macht

Fits to an exponential curve,

 

y = bemx.

Power

Fits to a power curve, y = bxm.

 

 

8-12

Statistics aplet