HP 12c Platinum - Power Curve Fit

104 Statistics
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
fCLEARH.
2.
Key in the first y-value and press
g°. Key in the first x-value and press
g°_. Repeat this step for all data pairs.
3.
Press
gR~, to obtain the correlation coefficient (between ln y and ln x).
4.
Press 0
gRg> to obtain A in the above equation.
5.
RPN: Press 1gR0gR~d- to obtain B.
5.
ALG: Press 1gR0gR-~d³ to obtain B.
6.
To make a y-estimate, key in the x-value and press
g°gRg>.
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 has fallen, he might have
released a rock from various levels of the Tower of Pisa (which was leaning even then)
and timed its descent by counting his pulse. The following data are measurements Galileo
might have made.
t (pulses) 2 2.5 3.5 4 4.5
h (feet) 30 50 90 130 150
B
> 1
0 < B <1
X
Y
0
B < 0
X
Y
0