Possible answers for the discussion: What is wrong with these data scenarios?

In this reading, you can find possible answers prepared by your tutor for the six data scenarios described in the discussion board at the end of Activity 1.

1. Car accidents

Possible answer:

• The graph is misleading because it is truncated. The scale on the vertical axis should start at zero so that the bars are in the correct proportions. A part of the vertical axis could be omitted, but the symbol // should be used to warn the reader of the modified axis.

2. TV sales

Possible answer:

• The area of the television image on the right is nine times (not three times) the area of the television on the left. The pictogram gives the visual impression that sales in 2022 were nine times the sales in 2012. A simple bar plot or pie chart would be a better choice.

3. Growth of expenditure

Possible answer:

• The bars are not drawn in the correct proportions. The vertical axis is missing.

4. Market share of supermarkets

Possible answer:

• The percentages do not add up to 100, and the Tesco slice seems too large for 27.2%. Also, contiguous colours are similar.
• Bar plot; we would merely have to identify the highest bar.

5. TV licence fees

Possible answer:

• The 2013 projection is located on the timeline where the 2007 observation would be plotted.
• A correct representation would require placing the 2013 projection at year 2013, i.e 7 time units to the right of the last observed value in 2006. This would make the growth look a lot less dramatic.

6. Terrorism and war in Iraq

Possible answer:

• Because the vertical axis does not start at zero, it appears that six times as many people are in the “no, not” column than in the “yes, safer” column.
• With a pie chart, the area of each slice represents the percentage of that category. Therefore, the relative sizes of the slices will always represent the relative percentages in each category.