Statistical Functions - HP -25 Owner's Handbook Manual

In working through complex equations, like the one containing
six levels of parentheses above, you really appreciate the value
of the Hewlett-Packard logic system. Because you calculate
one step at a time, you don't get "'lost'' within the problem. You
see every intermediate result, and you emerge from the calcula-
tion confident of your final answer.
Statistical Functions
Summations
Pressing the key automatically gives you several different
sums and products of the values in the X- and Y- registers at
once. In order to make these values accessible for sophisticated
statistics problems, they are automatically placed by the calcu-
lator into storage registers R; through R,. The only time that
information is automatically accumulated in the storage reg-
isters is when the key is used. Before you begin any calcu-
lations using the key, you should first clear the storage
registers of data by pressing| = [F-2].
When you key a number into the display and press the key,
each of the following operations is performed:
= The number that you keyed into the X-register is added
to the contents of storage register R;.
= The square of the number that you keyed into the X-
register is added to the contents of storage register R.
= The numberthat you keyed into the X-register is multiplied
by the contents of the Y-register, and the product added to
storage register R.
=« The number in the Y-register of the stack is added to the
contents of storage register R;.
« The number 1 is added to storage register R;, and the total
number in R, is then written into the display (The stack
does not lift).
Thus, each press of the key updates these summations and
multiplications. The contents of the displayed X-register and
the applicable storage registers are as follows:
Register Data
Displayed X n Number of entries.
R, n Number of entries.