Note:
Some
numbers
represent
only an
approximation
of the
actual
value.
Numbers
representing
voting
polls or
engineering
measurements
are two
examples.

To
quantify
the degree
of
possible
error,
Poll
numbers
are
reported
along with
a margin
of error.
The margin
or error
simply
means the
actual
result is
somewhere
within the
range
represented
by the
margin of
error.

For
example, a
poll of
likely
voters for
a ballot
proposition
might be
reported
something
like this:
35% in
favor,
with a
margin of
error of
plus or
minus 4%.
This means
that the
actual
number of
voters in
favor of
the ballot
measure
lies
somewhere
between
31% and
39% (35%
is half
way in
between).

**Example**:
Compare
the
following
poll
numbers -
35% in
favor of
candidate
"A"
and
37% in
favor of
candidate
"B"
. The
margin of
error for
both polls
is plus or
minus
3%.

If
these
numbers
are within
6% of one
another
(3% + 3% =
6%), the
poll
results
actually
overlap.
It is
impossible
to tell
which
number is
larger.
The
results
are a
statistical
tie.
*(Although
it is not
necessary
to draw a
number
line, a
number
line
provides a
visual
picture of
the
overlap in
the poll
results
for this
example.)*

(1)
Plot the
range for
both
numbers on
a number
line, and
then
(2)
look for
any
overlap.

Number
Line

The
4% overlap
on the
number
line shows
that
both
numbers
are so
close
together
that the
actual
value of
each
could fall
anywhere
within the
same 4%
range
.

It
is
impossible
to tell
which
number is
larger
than the
other.

The
poll
results of
35% and
37% are a
statistical
tie
.