<s>
The	O
normal	B-Application
probability	I-Application
plot	I-Application
is	O
a	O
graphical	B-Application
technique	I-Application
to	O
identify	O
substantive	O
departures	O
from	O
normality	O
.	O
</s>
<s>
This	O
includes	O
identifying	O
outliers	O
,	O
skewness	B-General_Concept
,	O
kurtosis	B-Error_Name
,	O
a	O
need	O
for	O
transformations	O
,	O
and	O
mixtures	O
.	O
</s>
<s>
Normal	B-Application
probability	I-Application
plots	I-Application
are	O
made	O
of	O
raw	O
data	O
,	O
residuals	O
from	O
model	O
fits	O
,	O
and	O
estimated	O
parameters	O
.	O
</s>
<s>
In	O
a	O
normal	B-Application
probability	I-Application
plot	I-Application
(	O
also	O
called	O
a	O
"	O
normal	O
plot	O
"	O
)	O
,	O
the	O
sorted	O
data	O
are	O
plotted	O
vs.	O
values	O
selected	O
to	O
make	O
the	O
resulting	O
image	O
look	O
close	O
to	O
a	O
straight	O
line	O
if	O
the	O
data	O
are	O
approximately	O
normally	O
distributed	O
.	O
</s>
<s>
The	O
normal	B-Application
probability	I-Application
plot	I-Application
is	O
a	O
special	O
case	O
of	O
the	O
Q	B-Application
–	I-Application
Q	I-Application
probability	O
plot	O
for	O
a	O
normal	O
distribution	O
.	O
</s>
<s>
The	O
theoretical	O
quantiles	O
are	O
generally	O
chosen	O
to	O
approximate	O
either	O
the	O
mean	O
or	O
the	O
median	O
of	O
the	O
corresponding	O
order	B-General_Concept
statistics	I-General_Concept
.	O
</s>
<s>
The	O
normal	B-Application
probability	I-Application
plot	I-Application
is	O
formed	O
by	O
plotting	O
the	O
sorted	O
data	O
vs.	O
an	O
approximation	O
to	O
the	O
means	O
or	O
medians	O
of	O
the	O
corresponding	O
order	B-General_Concept
statistics	I-General_Concept
;	O
see	O
rankit	B-Application
.	O
</s>
<s>
Different	O
sources	O
use	O
slightly	O
different	O
approximations	O
for	O
rankits	B-Application
.	O
</s>
<s>
The	O
formula	O
used	O
by	O
the	O
"	O
qqnorm	B-Application
"	O
function	O
in	O
the	O
basic	O
"	O
stats	O
"	O
package	O
in	O
R	B-Language
(	O
programming	O
language	O
)	O
is	O
as	O
follows	O
:	O
</s>
<s>
With	O
a	O
location-scale	O
family	O
of	O
distributions	O
,	O
the	O
location	O
and	O
scale	O
parameters	O
of	O
the	O
distribution	O
can	O
be	O
estimated	O
from	O
the	O
intercept	B-Algorithm
and	O
the	O
slope	O
of	O
the	O
line	O
.	O
</s>
<s>
This	O
is	O
a	O
sample	O
of	O
size	O
50	O
from	O
a	O
normal	O
distribution	O
,	O
plotted	O
as	O
both	O
a	O
histogram	O
,	O
and	O
a	O
normal	B-Application
probability	I-Application
plot	I-Application
.	O
</s>
<s>
This	O
is	O
a	O
sample	O
of	O
size	O
50	O
from	O
a	O
right-skewed	B-General_Concept
distribution	I-General_Concept
,	O
plotted	O
as	O
both	O
a	O
histogram	O
,	O
and	O
a	O
normal	B-Application
probability	I-Application
plot	I-Application
.	O
</s>
<s>
This	O
is	O
a	O
sample	O
of	O
size	O
50	O
from	O
a	O
uniform	O
distribution	O
,	O
plotted	O
as	O
both	O
a	O
histogram	O
,	O
and	O
a	O
normal	B-Application
probability	I-Application
plot	I-Application
.	O
</s>
