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20050501
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