HP 0012C-90001, User Manual

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80 80 80 80 Section 6: Section 6: Section 6: Section 6: Statistics Functions Statistics Functions Statistics Functions Statistics Functions
File name: HP 12c+_user's guide_English_E_HDP0F12AE03_062608 - Modified.doc Page: 80 of 213
Printed Date: 2021/6/16 Dimension: 14.8 cm x 21 cm
Linear Estimation Linear Estimation Linear Estimation Linear Estimation
With two-variable statistical data accumulated in the statistics registers, you can
estimate a new
y-value
(
yˆ
) given a new
x-value
, and estimate a new
x-value
(
xˆ
)
given a new
y-value
.
To calculate
yˆ
:
1. Key in a new x-value .
2. Press
gR
.
To calculate
xˆ
:
1. Key in a new y-value .
2. Press
gQ
.
Example: Example: Example: Example: Using the accumulated statistics from the preceding problem, estimate
the amount of sales delivered by a new salesperson working 48 hours per week.
Keystrokes Keystrokes Keystrokes Keystrokes Display Display Display Display
48
gQ
28,818.93 Estimated sales for a 48 hour
workweek.
The reliability of a linear estimate depends upon how closely the data pairs would,
if plotted on a graph, lie in a straight line. The usual measure of this reliability is
the correlation coefficient,
r
. This quantity is automatically calculated whenever
yˆ
or
xˆ
is calculated; to display it, press
~
. A correlation coefficient close to 1
or –1 indicates that the data pairs lie very close to a straight line. On the other
hand, a correlation coefficient close to 0 indicates that the data pairs do not lie
closely to a straight line; and a linear estimate using this data would not be very
reliable.
Example: Example: Example: Example: Check the reliability of the linear estimate in the preceding example by
displaying the correlation coefficient.
Keystrokes Keystrokes Keystrokes Keystrokes Display Display Display Display
~
0.90 The correlation coefficient is close to
1, so the sales calculated in the
preceding example is a good
estimate.
To graph the regression line, calculate the coefficients of the linear equation
y
=
A
+
Bx
.
1. Press 0
gR
to compute the y- intercept ( A ).
2. Press 1
gR~d~-
to compute the slope of the line (
B
).