HP 25

Function Keys 67
LY
Summation of y values.
R5 LXY Summation of products ofx and y values.
R6 Lx2 Summation of X2 values.
R7 LX Summation of x values.
In addition, the y-value present before the last press of the m
key is retained in the Y-register, while the x-value present be-
fore m
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. (I n the case of
the m key, recalling storage register contents or keying in a
number simply writes over the number of entries (11) that is dis-
played.
The stack does not lift.)
Example: Find LX , Lx2 , LY, and LXY for the paired values ofx
and y listed below.
Press
a ~
7 mmiD
5m
5 I:mim
3m
9 mmiD
8m
1317
1316
1315
1314
1313
Mean
Display
t 0.00
17.00
I
1 1.00
I
1 5.00
I
12.00
I
19. 00
I
13.00
I
116.00
I
1 98.00
I
1 122.00
1 21 . 00
13.00
Ensures that all storage registers
are
cleared to zero initially.
(Assumes no results remain
from previous example.)
First pair is summed: 11 = I.
Second pa ir is summed: 11 = 2.
All the data is summed; 11 = 3.
Sum ofx values from register R
7
•
Sum of squares of x values from
register
R, ;.
Sum of products of x a nd y values
from register
Ro.
Sum ofy values from regi ster R o! .
Number of entries (n = 3).
The mean (arithmetic average) of data entered and summed using
them key is available by using the [KJ (meal1)key. When you