- Graphs are encountered on a regular basis in magazines
and newspapers. They summarize data in pictorial and
concise ways. Graphing should be done throughout the
school year in a variety of subjects. An important life
skill is knowing how to organize and interpret data.
- D-8 Frequently data must be grouped to make them more
manageable. For example, if there were 20 different TV
programs selected as favourites, you may want to categorize
them as comedy, drama, entertainment, sports, and
others.
- D-9 A histogram is a graphical representation of the
frequency with which scores occur. In a histogram, each
bar represents a range of data. The data are usually
separated into categories, the occurrence of each value is
tallied in the appropriate category, and the count is
plotted.
- Line graphs are suitable for displaying continuous data
such as temperature or a person's growth in height.
- A circle graph clearly shows how a whole is divided
into parts. It can be prepared by taking a 10 cm strip of
paper and marking it into fractional parts. Mark off the
fractional amounts indicated by the data, and then form a
circle by joining the ends of the strip of paper.
- Encourage students to display data using different
graphs so that they can see that there is no best way to
graph information although some graphs are more effective
than others. Information collected from previous
activities should be graphed in two or more ways.
- When students graph data, encourage them to select an
appropriate scale and to draw a sketch before actually
constructing the graph. In most cases, the actual graph
can be drawn using computer software. (TL)
- D-10 Students should be aware that a picture of the
data is only a beginning and that there is more than one
way to represent the data. The data and the purpose for
collecting it often determine the type of graph that is
most effective for displaying the data.
- The appropriate scale for a graph depends on the range
of the data, the lowest and/or highest value, the type of
graph, etc.
- Students should be able to make a rough sketch of data
collected. However, the time required to make accurate,
neat graphs would be better spent in learning to read and
interpret graphs. In real-life situations, graphs are
usually constructed using computer software rather than
doing them manually. The NCTM booklet Dealing with Data
and Chance (1991) states that "even more important than
... (constructing graphs) are the abilities to understand
and interpret the various representations, to understand
the similarities and differences, and to make informed
decisions about which one(s) to use in communicating a
complete and honest picture for decision making" (p.
26).
- D-11 There are a variety of software packages that are
designed to prepare graphs of data. Certain spreadsheet
programs have graphing capabilities. If students are able
to use computer software to graph data, they can produce
more visually appealing graphs and can look at different
ways of representing data. Rather than students taking the
time to construct accurate graphs, the computer can draw
several different graphs and the students can use these to
determine which is the most effective in presenting the
data and why. However, students should have a good
understanding of the concepts involved in graphing data and
interpreting graphs before using computer software to do
the graphs. (TL)
- D-13 As with any other problem-solving activity,
students should reflect on the results obtained to decide
whether they are reasonable. How would the results have
changed if you had done something differently; e.g.: asked
a different question or used a different method of
collecting data? How can we determine the accuracy of the
data we use?
- Whenever students collect, organize, and display data,
they should try to determine what conclusions can be made
regarding the data. Can you infer results that were not
actually collected but would be consistent with the data
collected? (CCT)
