105
Power Curve Fit
Another method of analysis is the power curve or geometric curve. The
equation of the power curve is y = Ax
B
, and the values for A and B are
computed by calculations similar to linear regression. Some examples of
power curves are shown below.
The following keystrokes fit a power curve according to the equation ln y =
ln A + B(ln x):
1. Press CLEAR .
2. Key in the first y-value and press . Key in the first x-value and
press . Repeat this step for all data pairs.
3. Press , to obtain the correlation coefficient (between ln y
and ln x).
4. Press 0 to obtain A in the above equation.
5. Press 1 0 to obtain B.
6. To make a y-estimate, key in the x-value and press
.
Example: If Galileo had wished to investigate quantitatively the
relationship between the time (t) for a falling object to hit the ground and
the height (h) it hasfallen, he might have released a rock from various
0.99
Correlation coefficient (between y
and ln x).
1 0
1,066.15 Value of A.
4,069.93 Value of B.
8
9,529.34
Total units sold by end of eighth
month.
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