Linear Estimation - HP 0012C-90001 User Manual

80 80 Section 6: Statistics Functions Section 6: Statistics Functions
80 80 Section 6: Section 6: Statistics Functions Statistics Functions

Linear Estimation

Linear Estimation Linear Estimation Linear Estimation
With two-variable statistical data accumulated in the statistics registers, you can
y-value
estimate a new
y-value
given a new .
y ˆ
To calculate :
x-value
1. Key in a new
2. Press gR.
x ˆ
To calculate :
y-value
1. Key in a new
2. Press gQ.
Example: Using the accumulated statistics from the preceding problem, estimate Example: Example: Example:
the amount of sales delivered by a new salesperson working 48 hours per week.
Keystrokes Keystrokes Keystrokes Keystrokes
48gQ
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,
x ˆ
is calculated; to display it, press ~. A correlation coefficient close to 1
or
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: Check the reliability of the linear estimate in the preceding example by Example:
Example: Example:
displaying the correlation coefficient.
Keystrokes Keystrokes Keystrokes Keystrokes
~
To graph the regression line, calculate the coefficients of the linear equation
y A Bx
= + .
1. Press 0gR to compute the
2. Press 1gR~d~- to compute the slope of the line (
y ˆ
x-value
( ) given a new
.
.
Display Display Display Display
28,818.93
r
. This quantity is automatically calculated whenever
Display Display Display Display
0.90
y-
intercept (
, and estimate a new
Estimated sales for a 48 hour
workweek.
The correlation coefficient is close to
1, so the sales calculated in the
preceding example is a good
estimate.
A
).
x ˆ
x-value
( )
y ˆ
B
).