Understanding Graphing Worksheet
Graphs appear not only in textbooks and scientific journals, but
also in newspapers and popular magazines. They are useful
because they clearly show relationships between two or more
variables. Two of the most common graphs are bar and line
graphs.
Bar graphs compare several variables according to one
characteristic. For example, the bar graph below compares four
kinds of cereal according to the number of calories each contains
in 28 grams.
Number of Calories Compared to Brands of Cereal
100
110
120
130
Korn Krispi es Sugar Circles Oat Boats Honey Hunks
Brands of C ereal (28 grams)
Calories
1. Look at the numbers used on the vertical axis. What
would happen to the bars on the graph if these numbers
were changed to 100, 150, 200, and 300?
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2. How would the graph change if the numbers on the
vertical axis started with 0 and increased in increments
of 10?
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Line graphs, such as the one below, show a change in one
or more variables over time. They can also illustrate a trend.
Stud ents Enr olled in Ph ysical Sc ience an d
Chemistry at North High School Vs. Years
50
55
60
65
70
75
1984 1985 1986 1987 1988
Years
Number of Stu dents
Chemistry Physical Science
3. How does the enrollment in physical science compare
with that in chemistry over the years? Do you see any
trends?
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4. Why does this graph include a legend?
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Notice that the independent variables in both graphs (the kind of
Brands of Cereal and the Years) are plotted along the horizontal
axis. Independent variables are chosen or changed by the
experimenter. The dependent variables (the Number of Calories
and the Number of Students) are plotted along the vertical axis.
Dependent variables change when the independent variable
changes. Notice, too, that both graphs include titles and labels
for the variables.
To practice making a bar graph, let’s compare the number of
students in several high schools. School A has 850, school B
has 600, school C has 1200, school D has 900, and
school E has 350.
5. In a bar graph of these data, what would be the
independent variable and on which axis would it be
plotted?
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6. What would be the dependent variable and on which
axis would it be plotted?
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