# Lllplll

Topics: Difference, Graph theory Pages: 14 (452 words) Published: April 27, 2013
Data Literacy Project

DL
SPSeries:
10.19.11

Bar
Graphs
and
Histograms:
similarities
and
differences

A
description
from
Dr.
Math
[http://mathforum.org/dr.math/
]

Questioner:
“I'm
confused
which
graph
has
bars
that
touch
on
the
sides,
and
which
has
bars
that
are
separate.

Let's
say
6
girls
love
dogs,
5
love
cats,
and
2
love
hamsters.

A
bar
graph
would
represent
this
data
better
than
a
histogram,
right?”

Dr.
Math
replies:
A
histogram
is
a
KIND
of
bar
graph;
so
everything
that
a
bar
graph
is,
a
histogram
is
too.

But
there
are
special
things
a
histogram
that
are
not
true
of
ordinary
bar
graphs,
and
these
are
the
differences.

One
big
difference
is
what
they
are
used
for.

A
bar
graph
can
be
used
to
compare
ANY
group
of
numbers,
as
in
your
example
of
the
numbers
who
like
different
kinds
of
pets.

That
is
very
much
like
the
sort
of
frequency
distribution
that
histograms
display,
since
you
are
graphing
"frequencies";
but
the
bars
would
represent
categories,
not
numbers.

A
histogram
is
used
ONLY
when
the
bars
will
represent
different
numbers
or
intervals
along
an
axis.

For
example,
if
6
girls
pets
weighing
0
-­‐
3
pounds,
5
pets
weighing
3
-­‐
6
pounds,
and
2
pets
weighing
6
-­‐
9
pounds,
you
could
make
a
histogram
of
that.

As
a
result
of
this
difference,
we
make
the
bars
of
a
histogram
touch
-­‐-­‐that
way,
they
illustrate
the
idea
that
they
represent
sets
of
numbers,
and
that
together
they
cover
an
entire
range
of
values.

Discrete
bar
graphs
represent
separate
entities,
like
your
dogs,
cats,
and
hamsters,
and
therefore
are
drawn
separately,
with
space
between.
(Sometimes
histograms
are
drawn
with
spaces,
to
indicate
that
they
represent
discrete
numbers,
that
is,
integers,
rather
than
a
continuous
range
of
values.

Also,
sometimes
at
higher
levels,
the
intervals
can
be
different
sizes,
so
the
bars
have
different
widths.

Regular
bar
graphs
always
have
the
same
width,
because
the