A graph is simply a v isual representation of data collected which shows a relationship
betw een two variable measures. The follow ing guidelines are to be used w hen creating a
graph in science. The most important part of constructing a graph is determining w here to put
the information.
 The independent v ariable (I V) is alw ays placed on the x-axis. Remember, the
independent v ariable is the condition in the experiment that is being changed.
 The dependent v ariable (DV) is alw ays placed on the y-axis. The dependent v ariable is
the condition that is being observ ed or measured and results from changing the
independent v ariable.
 The title can be placed abov e or below the graph.
 A legend or key is placed to the right or below a graph show ing the results of multiple
tested or independent v ariables over time – especially true of a graph that show s a rate
or an ev ent occurring in time.
 All graphs should be at-least half a page in size w ith room for a summary statement.
Example:
Predator–Prey relationships effect on lynx and hare populations over 20 years
Time (years)
Scoring Rubric for all Graphs:
 Title – describes the relationship between the independent and dependent
variables
 Axis – dependent variable is always on y-axis
 Labels – each axis includes a label with units
 Scale – use a uniform scale and graph size should be 4” x 6” minimum
 Neatness – always use a ruler; write or print neatly
 Color – use color whenever possible, especially on bar graphs
Types of Graphs
Pie graphs are usually used to compare
proportions. They look like a pie cut into
different sized w edges, where the sizes of
each w edge represents a different category
of data. For example a pie graph can be
used to compare the proportion of students in
your class w ith blue, brow n or hazel colored
eyes. To draw a pie graph, use a compass,
conv ert your data to percentages then
conv ert the percentages to angle degrees –
remember there are 3600 in a circle.
Bar graphs are used to compare discrete
groups. Each group is represented by a bar
w hose height represents something about that
group. Usually each group is represented
across the x-axis and the y-axis represents the
data collected about each group. For
example a bar graph can be used to
compare the heights of boys v ersus girls in the
freshman class. A bar graph can also be used
to show a frequency distribution, where the yaxis show s the number of subjects in different categories. An example of this w ould be the
number of students w ho hav e birthdays in each month of the school year. Draw a bar graph
using a ruler to create the x and y-axis. Data is represented bars of equal w idth and v arying
height w hich is dependent on the data.
Scatter plots are used to look for relationships
betw een two numerical variables; often an
independent and dependent v ariable. The
independent v ariable is represented by the xaxis and the dependent v ariable on the y-axis.
For example, a scatter plot can be used to
graph the relationship betw een height and
shoe size of students in your class. Draw a
scatter plot graph using a ruler to create the x
and y-axis. Do not connect data points but
look for a trend that might demonstrate a relationship.
Line graphs are set up like scatter plots but there is usually only one “y” v alue for each “x’
v alue. Line graphs are used to show a relationship between an independent and dependent
v ariable or to show an ev ent over time (rate). For example, a line graph can be used to show
the change in heart rate after doing exercise until resting heart rate is reached. Draw a scatter
plot graph using a ruler to create the x and y-axis. Connect the data points to show the
relationship more clearly. See front for example of a line graph.