CEPD · Module 2 — Visual and information design for screens
Label units, cite sources, choose the right chart, keep it accessible, and never turn an effect size into a percentage.
About 18 min
Practice in the lesson player
Sorting, matching, quizzes, and the module gate stay behind a free account so scored answers are not public. The teaching notes below are the same cited curriculum.
01
A chart slide is evidence, not clip art. Production directors label the unit (percentage, median d, count), cite the source under the graphic, and limit the number of bars so phone users can read it. A bar chart labelled "% improvement" showing Mayer's d = 1.67 as "167%" is a false caption, and an expert reviewer will stop trusting the course.
02
Check | Why
Unit on the axis or in the title | Prevents confusing d, %, counts
Source and date under the chart | Fact-check trail
Seven bars or fewer on mobile | Readable without zoom
Values labelled directly, not only by colour | Colour-blind users and WCAG 1.4.1
Bars start at zero | Prevents exaggerated differences
A text summary of the key finding | Screen-reader users and quick readers
03
Send back: % improvement" axis showing effect sizes. · 3D pie with twelve slices. · Self-ratings shown as "skill levels
Ship: Median d" axis, source line: Mayer (2017). · Horizontal bars, five categories, values labelled. · Caption says "self-rated proficiency
04
WCAG 1.4.1 Use of Colour (A) means colour cannot be the only way to tell series apart; add labels or patterns. WCAG 1.4.11 Non-text Contrast (AA) asks for 3:1 contrast for chart elements needed to understand the data. Every chart needs a text alternative that states the finding, not "chart of results". In Arabic, horizontal bar charts usually work better than vertical ones because labels can run right-aligned at full length. Decide whether to mirror the axis: a time axis in Arabic charts is often kept left to right in technical contexts and mirrored in general audiences. Pick one rule for the course and apply it everywhere.
05
Add a chart template to your pattern sheet that passes every row of the QC table in both languages, including the text alternative.