20021201
Drawing a Power Regression Graph (
y
=
a
·
x
b
)
Power regression can be used when
y
is proportional to the power of
x
. The normal power
regression formula is
y
=
a
·
x
b
. If we obtain the logarithms of both sides, we get ln(
y
) = ln(
a
)
+
b
· ln(
x
). Next, if we say that X = ln(
x
), Y = ln(
y
), and A = ln(
a
), 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] [Power 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: PowerR
Tap
y
to draw the graph.
7-5-12
Graphing Paired-Variable Statistical Data
The following is the power regression model formula.
y
=
a
·
x
b
a
:
regression coefficient
b
:
regression power
r
:
correlation coefficient
r
2
:
coefficient of determination
MSe
: mean square error
• MSe
=
Σ
1
n
–
2
i
=1
n
(
ln
(
y
i
)
– (
ln
(
a
)
+
b·
ln
(
x
i
)))
2
