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Graph reading and scale

The Graph Reading and Scale: Student Worksheet is based on an actual classroom experience.

It provides the opportunity to diagnose students' understanding of graphical representations and helps students to develop critical thinking using a real context.


A class of students recorded the number of years their families had lived in their town. Here are two graphs that students drew to tell the story.

Graph 1. Stacked plot with horizontal scale increasing in equal increments of 5 years. Plot shows a positive skew. Graph 2. Stacked plot with horizontal scale marked in unequal increments. Plot shows a bimodal distribution.
  1. What are two things you can tell about Graph 1?
  2. What are two things you can tell about Graph 2?
  3. Describe the differences between Graph 1 and graph 2
  4. Which plot better tells the story of how long the students' families have lived in their town?


When students are asked to describe differences between the two plots, many do not realise that the same data are represented in each. It is common for students to focus on the general aesthetic appearance with little mathematical justification. Some students focus more explicitly on the layout. A few students acknowledge that the data are the same, only the scales are different.

The Graph Reading and Scale: Rubric with examples of students' responses can be downloaded.