HP 25 User Manual

70 Funclon K-
The correct values for mean and stand ard deviation are n ow
obtainable by pressing [Xl and ~ .
For example, suppose the 62-year old member of the sampl e
as given above were to lose his position as one of the wealthiest
persons because of a series of ill-advised investments in coc oa
futures. To account for the change in data if he were replaced
in the
sample by a 21-year old rock musician:
Press
62
D ~
21
Ell
Display
62.
9.00
21.
10.00
Data to be repla ced .
Number of entries (n) is now nine.
The new dat a.
Number of entries (n) is ten again .
The new data has been calculated into each of the summations
present in the storage registers. To see the new mean and
standard deviation:
Press
D@
DO
Display
60.30
17.09
The new average (mean) age.
The new standard deviation.
Vector Summations
The Ell key can be used to sum any quantities that are in the x-
and Y -registers. You can even perform vector addition and
subtraction using rectangular to polar coordinate conversion
and the Ell and ~ keys .
Example: In his converted Swordfish ai rcraft, grizzled bush
pilot Apeneck Sweeney reads an air speed of 150 knots and a
heading
of 045
0
from his instruments . The Swordfish is also
being buffeted by a
headwind of 40 knots from a bearing of 02 5° .
What is the a ctual ground speed and course of the Sw ord-
fish?
Method: The course and ground speed are equal to the s um
of the instrument vector and the wind vector. The vecto rs
are converted to rectangular coordinates and summed using
the Ell and [[] keys . Their sum is recalled by recalling the valu es
in storage registers R4 O:y) and R7 (Ix), and the new rect an-
gular coordinates are then converted back to polar coordin a te s

HP 25 Specifications

General

Power Source	Rechargeable battery pack
Programming Steps	49
Release Year	1975
Functions	Trigonometric, logarithmic, statistical
Type	Scientific
Dimensions	148 x 80 x 14 mm