When collecting, organizing and making sense of raw
data, often it is best to make use of bar and line graphs. If
comparing two sets of data we use double bar and double line graphs.

Say, for example, that 25
students were followed from age 14 to age 18 to record how
many of these students worked at each age level. The
following is the data that was collected:

14 yrs: 1 worked, 24 did not
work
15 yrs: 3 worked, 22 did not work
16 yrs: 11 worked, 14 did not work
17 yrs: 19 worked, 6 did not work
18 yrs: 22 worked, 3 did not work

The next step would
be to construct
a graph to read the data more easily.

Let's look at a double bar
graph first...

Be sure to:

Give the graph a title

Label the axes

Be consistent with the numbers

Use a key

Leave a space between the bars
as we go to the next age

Now let's construct a double
line graph using the same data: