7-5-9

Graphing Paired-Variable Statistical Data

Drawing a Logarithmic Regression Graph

Logarithmic regression expresses y as a logarithmic function of x. The normal logarithmic regression formula is y = a + b · ln(x). If we say that X = ln(x), then this formula corresponds to the linear regression formula y = a + b·X.

u ClassPad Operation

Start the graphing operation from the Statistics application’s Graph window or List window.

From the Graph window

Tap [Calc] [Logarithmic Reg] [OK] [OK] ".

From the List window

Tap [SetGraph][Setting...], or G.

On the Set StatGraphs dialog box that appears, configure a StatGraph setup with the setting shown below, and then tap [Set].

Type: LogR

Tap yto draw the graph.

The following is the logarithmic regression model formula.

y= a + b·ln(x)

a : regression constant term

b : regression coefficient

r : correlation coefficient

r2 : coefficient of determination

MSe : mean square error

 

1

 

n

• MSe =

 

Σ (yi – (a + b·ln (xi)))2

n –

2

 

i=1

20050501