<s>
That	O
is	O
,	O
in	O
a	O
concordant	B-General_Concept
pair	I-General_Concept
,	O
both	O
elements	O
of	O
one	O
pair	O
are	O
either	O
greater	O
than	O
,	O
equal	O
to	O
,	O
or	O
less	O
than	O
the	O
corresponding	O
elements	O
of	O
the	O
other	O
pair	O
.	O
</s>
<s>
The	O
Kendall	B-General_Concept
tau	I-General_Concept
distance	O
between	O
two	O
series	O
is	O
the	O
total	O
number	O
of	O
discordant	B-General_Concept
pairs	I-General_Concept
.	O
</s>
<s>
The	O
Kendall	B-General_Concept
tau	I-General_Concept
rank	I-General_Concept
correlation	I-General_Concept
coefficient	I-General_Concept
,	O
which	O
measures	O
how	O
closely	O
related	O
two	O
series	O
of	O
numbers	O
are	O
,	O
is	O
proportional	O
to	O
the	O
difference	O
between	O
the	O
number	O
of	O
concordant	B-General_Concept
pairs	I-General_Concept
and	O
the	O
number	O
of	O
discordant	B-General_Concept
pairs	I-General_Concept
.	O
</s>
<s>
An	O
estimate	O
of	O
Goodman	B-General_Concept
and	I-General_Concept
Kruskal	I-General_Concept
's	I-General_Concept
gamma	I-General_Concept
,	O
another	O
measure	O
of	O
rank	O
correlation	O
,	O
is	O
given	O
by	O
the	O
ratio	O
of	O
the	O
difference	O
to	O
the	O
sum	O
of	O
the	O
numbers	O
of	O
concordant	O
and	O
discordant	B-General_Concept
pairs	I-General_Concept
.	O
</s>
<s>
Somers	B-General_Concept
 '	I-General_Concept
D	I-General_Concept
is	O
another	O
similar	O
but	O
asymmetric	O
measure	O
given	O
by	O
the	O
ratio	O
of	O
the	O
difference	O
in	O
the	O
number	O
of	O
concordant	O
and	O
discordant	B-General_Concept
pairs	I-General_Concept
to	O
the	O
number	O
of	O
pairs	O
with	O
unequal	O
values	O
for	O
one	O
of	O
the	O
two	O
variables	O
.	O
</s>
