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COMPUTE
o
After all
data
are entered
(after last
III)
press
.
1II
to obtain
the
so-called "y-intercept" value at
point
O-the
point at which the trend
lin
e,
traveling
the
horizontal
axis
(time line),
intersects
the
vertical
axis
(representing
given
units
of quantity).
o
Enter
number
of time period
(any
time
value),
press • .
® Press
III
to
obtain
trend lin
e
value.
@
Repeat
step
®
to obtain
each successive
trend
value
per time
unit,
or go
back
to
step
0
to find
the
values
for a
unique
time
position.
Note 1: Time position can
be
seen
at
any time by pressing
x:y
key
-be
sure
to
press
x:y
again before
resuming.
Note 2: The slope
(change in units of
quantity
per time period)
of the
trend line
may be found by pressing
R+
Sample Case: Sales figures
for
a
six
month
period
are:
Month
.
1
2
3
4
5
6
Sales ($
in
thousands)
476
589
570
625
619
570
Generate a
linear
trend forecast
of
the
second six
months'
sales
level
based
on
the
first
six
month
s' sa
les.
How many
entries
are
there?
Find the
theoretical
forecast values for
the
second
six
months.
Solution
Enter:
CLEAR
.
CLX
See Displayed:
476111589111570111625111619111
570
III
~
. .
number
of
entries
COMPUTE
.
111
7.111
III
• $
•
$
~
$
49
value of sales
trend
lin
e
at month 0
extrapol
ated sales
at
month
7
extrapolated
sales
at
month
8
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