HP HP-11C - Page 59

Section 3: Numeric Functions 57
such data by keying in only the differences between each value and
a number approximating the average of the values. This number
must be added to the result of calculating x, y, or the y-intercept of
L.R. For example, if your x values consist of 665999, 666000, and
666001, you should enter the data as -1, 0, and 1. If afterwards you
calculate x, add 666000 to the answer. In some cases the calculator
cannot compute s, r, L.R., or y with data values that are too close to
each other; and if you attempt to do so, the calculator will display
Error 2. This will not happen, however, if you normalize the data
as described above.
Note: Unlike storage register arithmetic, the and
operations allow overflow to occur in storage registers R
through Rg without indicating Error 1 in the display.
You can recall any of the statistics accumulations to the displayed
X-register by pressing and the number of the data storage
register holding the desired statistical accumulation. If you want to
recall both the Xx and 3y statistics, press (£+]). This
simultaneously copies Zx from R, into the displayed X-register and
copies 3y from Rjinto the Y-register. (Pressing causes the
stack to lift in the same way that it would if you keyed in two
numbers in sequence.)
Example. Electrical energy re-
searcher Helen 1. Voltz suspects a
possible relationship between the rise
in worldwide coal production in the
years 1972 through 1976 and a
similar rise in worldwide electricity
output for the same period. To assist
in a study of the data, Voltz will use
her HP-11C to accumulate the coal
production and electrical output sta-
tistics. Find Zx, 3x2, 3y, 3y2, and
S.xy for the paired x and y values of
Voltz’s data.