Graphing
Drawing a Exponential Regression Graph ( y = a·bx)
Exponential regression can be used when y is proportional to the exponential function of x. The normal exponential regression formula in this case is y = a·bx. If we take the natural logarithms of both sides, we get ln(y) = ln(a) + (ln(b)) · x. Next, if we say that Y = ln(y),
A = ln(a) and B = ln(b), the 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] [abExponential 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: abExpR
Tap yto draw the graph.
The following is the exponential regression model formula in this case.
y= a·bx
a : regression coefficient
b : regression constant term
r : correlation coefficient
r2 : coefficient of determination
MSe : mean square error
| 1 | n | |
• MSe = | Σ (ln (yi) – (ln (a) + (ln (b)) . xi))2 | ||
n – 2 | |||
| i=1 |
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