<s>
In	O
industrial	O
statistics	O
,	O
the	O
X-bar	B-Application
chart	I-Application
is	O
a	O
type	O
of	O
Shewhart	O
control	B-General_Concept
chart	I-General_Concept
that	O
is	O
used	O
to	O
monitor	O
the	O
arithmetic	O
means	O
of	O
successive	O
samples	O
of	O
constant	O
size	O
,	O
n	O
.	O
This	O
type	O
of	O
control	B-General_Concept
chart	I-General_Concept
is	O
used	O
for	O
characteristics	O
that	O
can	O
be	O
measured	O
on	O
a	O
continuous	O
scale	O
,	O
such	O
as	O
weight	O
,	O
temperature	O
,	O
thickness	O
etc	O
.	O
</s>
<s>
The	O
X-bar	B-Application
chart	I-Application
is	O
always	O
used	O
in	O
conjunction	O
with	O
a	O
variation	O
chart	O
such	O
as	O
the	O
and	O
R	O
chart	O
or	O
and	O
s	O
chart	O
.	O
</s>
<s>
The	O
R-chart	O
shows	O
sample	O
ranges	O
(	O
difference	O
between	O
the	O
largest	O
and	O
the	O
smallest	O
values	O
in	O
the	O
sample	O
)	O
,	O
while	O
the	O
s-chart	O
shows	O
the	O
samples	O
 '	O
standard	B-General_Concept
deviation	I-General_Concept
.	O
</s>
<s>
The	O
R-chart	O
was	O
preferred	O
in	O
times	O
when	O
calculations	O
were	O
performed	O
manually	O
,	O
as	O
the	O
range	O
is	O
far	O
easier	O
to	O
calculate	O
than	O
the	O
standard	B-General_Concept
deviation	I-General_Concept
;	O
with	O
the	O
advent	O
of	O
computers	O
,	O
ease	O
of	O
calculation	O
ceased	O
to	O
be	O
an	O
issue	O
,	O
and	O
the	O
s-chart	O
is	O
preferred	O
these	O
days	O
,	O
as	O
it	O
is	O
statistically	O
more	O
meaningful	O
and	O
efficient	O
.	O
</s>
<s>
Depending	O
on	O
the	O
type	O
of	O
variation	O
chart	O
used	O
,	O
the	O
average	O
sample	O
range	O
or	O
the	O
average	O
sample	O
standard	B-General_Concept
deviation	I-General_Concept
is	O
used	O
to	O
derive	O
the	O
X-bar	B-Application
chart	I-Application
's	O
control	O
limits	O
.	O
</s>
