40 Section 3: Numeric Functions
The data are compiled as follows:
When you execute z, the number previously
in the X-register is placed in the LAST X
register and the updated n-value is placed in X.
The number previously in the Y-register is not
changed.
You can recall any of the accumulated
statistics to the display (X-register) by
pressing l and the number of the data
storage register containing the desired statistic.
Example. Electrical energy researcher Helen I.
Voltz suspects a possible relationship between the
rise in worldwide coal production in the years1972
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-10C to
accumulate the coal production and electrical
output statistics. Find ∑x, ∑x
2
, ∑y, ∑y
2
, and ∑xy
for the paired x- and y-values of Voltz’s data.
*
*Note: Some sets of data points consist of a series of x-values (or y-values) that differ
from each other by a comparatively small amount. You can maximize the precision of
any statistical calculation involving 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 xyx
ˆ
,
ˆ
, or the y-intercept of L. 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
,
ŷ
, or x
ˆ
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.
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