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Drawing an Exponential Regression Graph (
y
=
a
·
b
x
)
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
·
b
x
. 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
y
to draw the graph.
7-5-11
Graphing Paired-Variable Statistical Data
The following is the exponential regression model formula in this case.
y
=
a
·
b
x
a
: regression coefficient
b
: regression constant term
r
: correlation coefficient
r
2
: coefficient of determination
MSe
: mean square error
• MSe =
Σ
1
n – 2
i=1
n
(ln (yi) – (ln (a) + (ln (b))
.
xi))
2