Instructor Notes

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notes about what has worked in this section

The Importance of Message


Instructor Note

Learners who have less experience with tabular data may need more specific information than this section provides. If you want to include more teaching about managing and cleaning tabular data, consider pairing this lesson with the Data Carpentry Ecology Data in Spreadsheets lesson.



Graphical Elements of a Chart


Possible answers

Some possible answers to this discussion include:

  • Scatter chart: points on one or more scales
  • Bar chart: length, area, shading or color
  • Pie chart: angle, curvature, area, shading or color

Spreadsheet programs and other software can turn most two-dimensional charts into three-dimensional charts. Use examples such as three-dimensional pie and bar charts to incorporate volume into this discussion.



Shading and color discussion

With enough time, you may choose to structure the questions about shading and color as a discussion or brainstorm in the shared document. Some rationale for each question is included below.

  • How many categories am I working with?
    • Using color to differentiate more than 4-5 categories can make the colors too similar to each other.
  • Are my colors accessible?
    • Color blindness can affect how people perceive certain colors and color combinations, e.g.: red/green and blue/yellow.
    • People with visual impairments have difficulty perceiving low-contrast colors.
  • What assumptions are my colors making?
    • Relying on specific contrasting colors, e.g.: red/green or red/yellow/green, to communicate a message assumes that the colors mean the same thing to your audience that they do to you.
  • How will my chart be distributed?
    • Printing and photocopying can distort or erase gray and color tones.
    • Monitors and projectors cannot always replicate color accurately.


Instructor Note

Depending on time and your learners’ interest, this definition of worse charts can be a place to point out that charts that deliberately obscure a message or mislead an audience often include multiple components that are more difficult to perceive accurately. Learners can use this knowledge to bring a critical lens to charts they come across in ordinary life.



Instructor Note

To wrap up the challenge, have learners share whether and how their opinions about the charts in the two use cases differ from the advice on visual properties discussed in the lesson. This can happen in the shared document or aloud during a brief discussion of the solutions. The correct answers correspond to the information in the section, “Better Visual Representations.” Any points of disagreement are good places to reinforce that:

  • Data visualization is both art and science.
  • Previous experience with reading charts can influence which chart styles we expect for communicating specific kinds of information.
    • For example, pie charts are often used to communicate part/whole information, but they may not be better for accurate perception, especially for many parts of one whole.


Identify and Interpret the Message


Communicating the Message


Instructor Note

Other tools can have many advantages as well. Certain software which use a command line interface may have a steeper learning curve, but has other advantages such as improved reproducibility.