HP 12c Platinum Reference Manual page 103

Example 1: A manufacturer observes declining sales of a soon-to-be obsolete product, of
which there were originally 10,000 units in inventory. The cumulative sales figures over a
number of months, given below, may be approximated by a logarithmic curve of the form
y = A + B (ln x ), where y represents cumulative sales in units and x the number of months
since the beginning. How many units will be sold by the end of the eighth month?
1
Month
Cumulative 1431
Sales (units)
12c platinum / 12C
RPN Keystrokes
fCLEARH
1431\
1g°_
3506\
2g°_
5177\
3g°_
6658\
4g°_
7810\
5g°_
8592\
6g°_
gR~
1gR0gR
~d-
8g°gR
2
3506
12c platinum
ALG Keystrokes
fCLEARH
1431³
1g°_
3506³
2g°_
5177³
3g°_
6658³
4g°_
7810³
5g°_
8592³
6g°_
gR~
1gR0gR
-~d³
8g°gR
3 4
5177 6658
Display
First pair data input.
1.00
Second pair data input.
2.00
Third pair data input.
3.00
Fourth pair data input.
4.00
Fifth pair data input.
5.00
Sixth pair data input.
6.00
Correlation coefficient
0.99
(between y and ln x).
Value of A.
1,066.15
Value of B.
4,069.93
Total units sold by end of
9,529.34
eighth month.
Statistics 103
5 6
7810 8592
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