A single Pearson distribution, 
is characterized by four parameters
, 
, 
, and 
.
describes the position of the peak, the
straggle, is the skewness which indicates the tilting of the
profile, and is the kurtosis which tells the flatness at the top
of the profile.
The concentration, 
of some impurity, at any given point, 
in
Silicon is given by:
The Pearson type IV function is implemented in SUPREM3 [38] as:
For a dual Pearson approach, two sets of the above four parameters are
needed, plus a ninth parameter describing the relative proportions of the
two Pearson's.
If 
and 
denote the two Pearson distributions,
describing the region of the profile closest to the surface
and describing the deeper channeled region, then the two
sets of parameters are 
, 
, 
,
and 
for use in 
and
, 
, 
,
and 
for use in 
.
The concentration 
at any position is:
is the concentration at the peak of the distribution
and 
is the ratio describing the relative proportions of the two
Pearson functions (the ninth parameter).