<s>
In	O
statistics	O
,	O
the	O
Fano	B-General_Concept
factor	I-General_Concept
,	O
like	O
the	O
coefficient	O
of	O
variation	O
,	O
is	O
a	O
measure	O
of	O
the	O
dispersion	O
of	O
a	O
counting	O
process	O
.	O
</s>
<s>
where	O
is	O
the	O
standard	B-General_Concept
deviation	I-General_Concept
and	O
is	O
the	O
mean	O
number	O
of	O
events	O
of	O
a	O
counting	O
process	O
after	O
some	O
time	O
.	O
</s>
<s>
The	O
Fano	B-General_Concept
factor	I-General_Concept
can	O
be	O
viewed	O
as	O
a	O
kind	O
of	O
noise-to-signal	O
ratio	O
;	O
it	O
is	O
a	O
measure	O
of	O
the	O
reliability	O
with	O
which	O
the	O
waiting	O
time	O
random	O
variable	O
can	O
be	O
estimated	O
after	O
several	O
random	O
events	O
.	O
</s>
<s>
For	O
a	O
counting	O
process	O
,	O
the	O
Fano	B-General_Concept
factor	I-General_Concept
after	O
a	O
time	O
is	O
defined	O
as	O
,	O
</s>
<s>
Sometimes	O
,	O
the	O
long	O
term	O
limit	O
is	O
also	O
termed	O
the	O
Fano	B-General_Concept
factor	I-General_Concept
,	O
</s>
<s>
Since	O
we	O
have	O
that	O
the	O
right	O
hand	O
side	O
is	O
equal	O
to	O
the	O
square	O
of	O
the	O
coefficient	O
of	O
variation	O
,	O
the	O
right	O
hand	O
side	O
of	O
this	O
equation	O
is	O
sometimes	O
referred	O
to	O
as	O
the	O
Fano	B-General_Concept
factor	I-General_Concept
as	O
well	O
.	O
</s>
<s>
When	O
considered	O
as	O
the	O
dispersion	O
of	O
the	O
number	O
,	O
the	O
Fano	B-General_Concept
factor	I-General_Concept
roughly	O
corresponds	O
to	O
the	O
width	O
of	O
the	O
peak	O
of	O
.	O
</s>
<s>
As	O
such	O
,	O
the	O
Fano	B-General_Concept
factor	I-General_Concept
is	O
often	O
interpreted	O
as	O
the	O
unpredictability	O
of	O
the	O
underlying	O
process	O
.	O
</s>
<s>
In	O
particle	B-Algorithm
detectors	I-Algorithm
,	O
the	O
Fano	B-General_Concept
factor	I-General_Concept
results	O
from	O
the	O
energy	O
loss	O
in	O
a	O
collision	O
not	O
being	O
purely	O
statistical	O
.	O
</s>
<s>
where	O
the	O
factor	O
of	O
2.35	O
relates	O
the	O
standard	B-General_Concept
deviation	I-General_Concept
to	O
the	O
FWHM	O
.	O
</s>
<s>
The	O
Fano	B-General_Concept
factor	I-General_Concept
is	O
material	O
specific	O
.	O
</s>
<s>
Measuring	O
the	O
Fano	B-General_Concept
factor	I-General_Concept
is	O
difficult	O
because	O
many	O
factors	O
contribute	O
to	O
the	O
resolution	O
,	O
but	O
some	O
experimental	O
values	O
are	O
:	O
</s>
<s>
The	O
Fano	B-General_Concept
factor	I-General_Concept
is	O
used	O
in	O
neuroscience	O
to	O
describe	O
variability	O
in	O
neural	O
spiking	O
.	O
</s>
<s>
Often	O
,	O
the	O
limit	O
definition	O
of	O
the	O
Fano	B-General_Concept
factor	I-General_Concept
is	O
used	O
,	O
for	O
which	O
,	O
</s>
<s>
While	O
most	O
work	O
assumes	O
a	O
constant	O
Fano	B-General_Concept
factor	I-General_Concept
,	O
recent	O
work	O
has	O
considered	O
neurons	O
with	O
non-constant	O
Fano	B-General_Concept
factors	I-General_Concept
.	O
</s>
<s>
In	O
this	O
case	O
,	O
it	O
is	O
found	O
that	O
non-constant	O
Fano	B-General_Concept
factors	I-General_Concept
can	O
be	O
achieved	O
by	O
introducing	O
both	O
noise	O
and	O
non-linearity	O
to	O
the	O
rate	O
of	O
the	O
underlying	O
Poisson	O
process	O
.	O
</s>
