HP HP-15C

54 Section 4: Statistics Functions
Example: Calculate the standard deviation about the mean calculated
above.
Keystrokes
Display
|S
31.62
Standard deviation about the mean nitrogen
application,  x.
®
1.24
Standard deviation about the mean grain
yield,  y.
Linear Regression
Linear regression is a statistical method for finding a straight line that best
fits a set of two or more data pairs, thus providing a relationship between
two or more data pairs, thus providing a relationship between two variables.
By the method of least squares, ´L will calculate the slope, A, and y-
intercept, B, of the linear equation:
y=Ax+B
1.
Accumulate the statistics of your data using the z key.
2.
Press ´L. The y-intercept, B, appears in the display (X-
register). The slope, A, is copied simultaneously into the Y-
register.
3.
Press ® to view A. (As is the case with the functions ’
and S, L causes the stack to lift two registers if it's
enabled, one if not).
T
t
y
y
Z
z
x
y
Y
y
A
slope
B
y-intercept
X
x
B
y-intercept
A
slope
Keys:
´L
®
The slope and y-intercept of the least squares line of the accumulated data
are calculated using the equations shown in appendix A.