68
<""unction
Ke\'~
pressD
rn
, the mean
of
the values
of
x
is
ca
lc
ul
at
ed
using the
data
in
storage registers R3
(n)
and R
7
(lx)
and the form
ul
a:
n
-
I"
x = - L.J
Xi
n i = 1
The
easiest way to accumulate the required d
ata
in
the appli-
cab
le registers
is
through the use
of
the
Ell
key as described
above.
However,
the required data may also be stored directly
in
storage registers R3
(n)
and R7
(lx)
, if desired.
Example: A
survey
found ten
of
the wealthi
est
persons
in
the
United States to have the following ages:
62
84
47
58
68 60
62
59
71
73
To
find the average (mean) age
of
this sample
of
wealthy
persons:
Press Display
0.00
1 Storage registers
~-'=
'----'
62
Ell
,
84
Ell
,
47
Ell
,
58
Ell
,
68
Ell
,
60
Ell
,
62
Ell ,
59
Ell
'
and X-register
cleared to zero.
71
Ell
,
73
Ell
1,-
1-0.-
00
----,1
N umber
of
entries.
D
rn
1 64.40 1 A verage (mean) age
in years.
Standard Deviation
The
standard deviation (a measure
of
dispersion around the
mean)
is
calc
ul
ated usi
ng
data
in
the
app
li
cab
le storage registers
and
the
@]
(standard
deviation)
key. Pressing
@]
uses the
data
in
registers R3lll),
Ru
(lx
2
),
and
R7
(lx)
to calculate the standard
deviation according to the formula:
n-I
S
=
J"
2
(lX)2
x L.J x -
--
n
For
examp
le, to
obta
in
the
samp
le deviation
in
the above
problem:
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