<s>
The	O
Chow	B-General_Concept
test	I-General_Concept
(	O
)	O
,	O
proposed	O
by	O
econometrician	O
Gregory	O
Chow	O
in	O
1960	O
,	O
is	O
a	O
test	O
of	O
whether	O
the	O
true	O
coefficients	O
in	O
two	O
linear	B-General_Concept
regressions	I-General_Concept
on	O
different	O
data	O
sets	O
are	O
equal	O
.	O
</s>
<s>
In	O
program	O
evaluation	O
,	O
the	O
Chow	B-General_Concept
test	I-General_Concept
is	O
often	O
used	O
to	O
determine	O
whether	O
the	O
independent	O
variables	O
have	O
different	O
impacts	O
on	O
different	O
subgroups	O
of	O
the	O
population	O
.	O
</s>
<s>
The	O
null	B-General_Concept
hypothesis	I-General_Concept
of	O
the	O
Chow	B-General_Concept
test	I-General_Concept
asserts	O
that	O
,	O
,	O
and	O
,	O
and	O
there	O
is	O
the	O
assumption	O
that	O
the	O
model	O
errors	O
are	O
independent	O
and	O
identically	O
distributed	O
from	O
a	O
normal	O
distribution	O
with	O
unknown	O
variance	O
.	O
</s>
<s>
The	O
test	O
statistic	O
follows	O
the	O
F-distribution	B-General_Concept
with	O
and	O
degrees	O
of	O
freedom	O
.	O
</s>
<s>
The	O
null	B-General_Concept
hypothesis	I-General_Concept
of	O
joint	O
insignificance	O
of	O
D	O
can	O
be	O
run	O
as	O
an	O
F-test	O
with	O
degrees	O
of	O
freedom	O
(	O
DoF	O
)	O
.	O
</s>
<s>
Some	O
software	O
like	O
SAS	O
will	O
use	O
a	O
predictive	O
Chow	B-General_Concept
test	I-General_Concept
when	O
the	O
size	O
of	O
a	O
subsample	O
is	O
less	O
than	O
the	O
number	O
of	O
regressors	O
.	O
</s>
