HP HP-25 - Page 71

R, Sy Summation of y values.
R, Xy Summation of products of x and y values.
R 3. x? Summation of x? values.
R, 3x Summation of x values.
In addition, the y-value present before the last press of the
key is retained in the Y-register, while the x-value present be-
fore was pressed is retained in the LAST X register.
To see any of the summations at any time, you have only to re-
call the contents of the desired storage register. (In the case of
the key, recalling storage register contents or keying in a
number simply writes over the number of entries (1) that is dis-
played. The stack does not lift.)
Example: Find 2x, 3x2, 3y, and 2xy for the paired values of x
and y listed below.
Press Display
K [rec] Ensures that all storage registers
are cleared to zero initially.
(Assumes no results remain
from previous example.)
7
5
First
pair
is
summed;
n
=
1.
5
3
2.00
Second
pair
is
summed;
n
=
2.
9
8
All
the
data
is
summed;
n
=
3.
7
16.00
Sum
of
x
values
from
register
R..
[RreL
[
98.00
Sum
of
squares
of
x
values
from
register Ry.
s 122.00 Sum of products of x and y values
from register R;.
=4
21.00
Sum
of'y
values
from
register
R,.
3
Number
of
entries
(n
=
3).
Mean
The
mean
(arithmetic
average)
of
data
entered
and
summed
using
the
BB
key
is
available
by
using
the[Z]
(mean)key.
When
you