<s>
In	O
statistics	O
,	O
a	O
volcano	B-Application
plot	I-Application
is	O
a	O
type	O
of	O
scatter-plot	B-Application
that	O
is	O
used	O
to	O
quickly	O
identify	O
changes	O
in	O
large	O
data	O
sets	O
composed	O
of	O
replicate	O
data	O
.	O
</s>
<s>
A	O
volcano	B-Application
plot	I-Application
combines	O
a	O
measure	O
of	O
statistical	B-General_Concept
significance	I-General_Concept
from	O
a	O
statistical	O
test	O
(	O
e.g.	O
,	O
a	O
p	B-General_Concept
value	I-General_Concept
from	O
an	O
ANOVA	B-General_Concept
model	O
)	O
with	O
the	O
magnitude	O
of	O
the	O
change	O
,	O
enabling	O
quick	O
visual	O
identification	O
of	O
those	O
data-points	O
(	O
genes	O
,	O
etc	O
.	O
)	O
</s>
<s>
that	O
display	O
large	O
magnitude	O
changes	O
that	O
are	O
also	O
statistically	B-General_Concept
significant	I-General_Concept
.	O
</s>
<s>
A	O
volcano	B-Application
plot	I-Application
is	O
constructed	O
by	O
plotting	O
the	O
negative	O
logarithm	O
of	O
the	O
p	B-General_Concept
value	I-General_Concept
on	O
the	O
y	O
axis	O
(	O
usually	O
base	O
10	O
)	O
.	O
</s>
<s>
This	O
results	O
in	O
data	O
points	O
with	O
low	O
p	B-General_Concept
values	I-General_Concept
(	O
highly	O
significant	O
)	O
appearing	O
toward	O
the	O
top	O
of	O
the	O
plot	O
.	O
</s>
<s>
These	O
represent	O
values	O
that	O
display	O
large	O
magnitude	O
fold	O
changes	O
(	O
hence	O
being	O
left	O
or	O
right	O
of	O
center	O
)	O
as	O
well	O
as	O
high	O
statistical	B-General_Concept
significance	I-General_Concept
(	O
hence	O
being	O
toward	O
the	O
top	O
)	O
.	O
</s>
<s>
Volcano	B-Application
plots	I-Application
are	O
also	O
used	O
to	O
graphically	O
display	O
a	O
significance	O
analysis	O
of	O
microarrays	O
(	O
SAM	O
)	O
gene	O
selection	O
criterion	O
,	O
an	O
example	O
of	O
regularization	O
.	O
</s>
<s>
the	O
strength	O
of	O
a	O
statistical	O
signal	O
,	O
and	O
y	O
axis	O
is	O
related	O
to	O
a	O
measure	O
of	O
the	O
statistical	B-General_Concept
significance	I-General_Concept
of	O
the	O
signal	O
.	O
</s>
<s>
a	O
point	O
in	O
a	O
volcano	B-Application
plot	I-Application
represents	O
a	O
single-nucleotide	O
polymorphism	O
.	O
</s>
<s>
or	O
a	O
Chi-square	B-General_Concept
test	I-General_Concept
statistic	O
.	O
</s>
<s>
Volcano	B-Application
plots	I-Application
show	O
a	O
characteristic	O
upwards	O
two	O
arm	O
shape	O
because	O
the	O
x	O
axis	O
,	O
i.e.	O
</s>
