Learning objectives
You can:
- Classify an analytical message into one of the seven types (comparison, change over time, composition, relationship, distribution, ranking, deviation) from the sentence a chart is meant to prove, and show how rewriting the sentence changes the type.
- Run the shared form heuristic on six stated inputs and return a primary form, a permitted alternate and the forms that are ruled out, matching what the drills and the slide checker return for the same inputs.
- Choose between a column and a bar on label length and category count, and compute the label width a slide of a stated size actually gives you.
- Select a form for change over time from the number of periods, the number of series and the sampling interval, and state what a two-period form throws away.
- Choose a composition form among stacked bar, hundred-percent stacked bar, waterfall and treemap, and prove from the angle arithmetic why a pie above three slices fails.
- Read and defend a scatter plot, computing the correlation and the share of variance it leaves unexplained, and state exactly what the chart licenses you to claim.
- Choose among histogram, box plot and dot plot for a distribution, and name what each one hides, including the bimodality a box plot cannot show.
- Rule out the four permanent fails (three-dimensional effects, dual axes, truncated bar baselines, the pie with a legend) and compute the distortion each one introduces, including a lie factor.
- Decide the axis questions on their own merits: the zero baseline where the mark encodes length, the log scale where the message is a rate, and the break that must be declared.
- Decide when a table or a sentence beats a chart, and defend a sort order as the claim it is.
Prerequisites & connections
Builds on. Nothing hard. This is a branch entry and the arithmetic never goes beyond percentages, ratios and a correlation you can compute in a spreadsheet. PR1.03 is the recommended run-up, because a learner who can already build shapes, tables and objects cleanly will spend their attention here on the choice rather than on the construction. If you have not done it, nothing below breaks: every chart is specified in words and in a table, so you can answer every question with a pencil.
Feeds forward. PR2.02 takes the form you chose here and strips it down: data ink, the eight deletions, pre-attentive attributes and the colour formula that makes one series carry the message. PR2.03 puts the sentence on top of it, turning a correct form into an argument with an action title, a single focal point and a small-multiple grid where one chart cannot hold the series. PR3.01 handles the diagrams that are not charts at all, where the content is a relationship between ideas rather than between numbers. PR4.02 stacks the titles across a whole deck so the chart-level claims add up to a case. The chart-choice drill set, thirty situations graded against the heuristic below, is the gate that goes with this node.
Six neighbours own material that touches this one and none of it is rebuilt here. PR0.01 owns the one-sentence takeaway, the audience profile and the medium choice, and carries a deliberately shallow six-line grammar table so that its own examples can name a chart without teaching the grammar. PR2.02 owns colour, and every chart specified below is described in terms of accent and neutral rather than in named colours for that reason. PR2.03 owns the action title, small multiples as a layout device and the dashboard, so the titles quoted below are written correctly but not taught. M10.03 owns the written deliverable, the memo and the report, and it is where the lie factor is taught inside a written exhibit rather than a slide. DA1.04 owns plotting in Python, including the library calls and the axis objects, and it assumes the choice made here. CN1.03 owns the answer-first synthesis that produces the message a chart then has to prove. Where a section below names one of those ideas it names it and moves on.