<s>
These	O
two	O
measures	O
are	O
obtained	O
through	O
a	O
design	O
based	O
on	O
the	O
construction	O
of	O
a	O
series	O
of	O
trajectories	B-Application
in	O
the	O
space	O
of	O
the	O
inputs	O
,	O
where	O
inputs	O
are	O
randomly	O
moved	O
One-At-a-Time	O
(	O
OAT	O
)	O
.	O
</s>
<s>
Each	O
trajectory	B-Application
is	O
composed	O
of	O
points	O
since	O
input	O
factors	O
move	O
one	O
by	O
one	O
of	O
a	O
step	O
in	O
while	O
all	O
the	O
others	O
remain	O
fixed	O
.	O
</s>
<s>
Along	O
each	O
trajectory	B-Application
the	O
so-called	O
elementary	O
effect	O
for	O
each	O
input	O
factor	O
is	O
defined	O
as	O
:	O
</s>
<s>
Usually	O
~	O
4-10	O
,	O
depending	O
on	O
the	O
number	O
of	O
input	O
factors	O
,	O
on	O
the	O
computational	O
cost	O
of	O
the	O
model	O
and	O
on	O
the	O
choice	O
of	O
the	O
number	O
of	O
levels	O
,	O
since	O
a	O
high	O
number	O
of	O
levels	O
to	O
be	O
explored	O
needs	O
to	O
be	O
balanced	O
by	O
a	O
high	O
number	O
of	O
trajectories	B-Application
,	O
in	O
order	O
to	O
obtain	O
an	O
exploratory	O
sample	O
.	O
</s>
<s>
The	O
two	O
measures	O
and	O
are	O
defined	O
as	O
the	O
mean	O
and	O
the	O
standard	B-General_Concept
deviation	I-General_Concept
of	O
the	O
distribution	O
of	O
the	O
elementary	O
effects	O
of	O
each	O
input	O
:	O
</s>
<s>
An	O
efficient	O
technical	O
scheme	O
to	O
construct	O
the	O
trajectories	B-Application
used	O
in	O
the	O
EE	O
method	O
is	O
presented	O
in	O
the	O
original	O
paper	O
by	O
Morris	O
while	O
an	O
improvement	O
strategy	O
aimed	O
at	O
better	O
exploring	O
the	O
input	O
space	O
is	O
proposed	O
by	O
Campolongo	O
et	O
al	O
..	O
</s>
