What is assertion evidence slide design?

Two parts, one message

The assertion evidence approach, as described on the site Michael Alley maintains, replaces the default phrase headline and bullet list with a succinct message, the assertion, supported by visual evidence rather than a bulleted list. The assertion is a full sentence, usually one or two lines, that says what the audience should conclude from the slide. The evidence is visual: a graph, a photograph, a drawing, an equation set large, or a short table. Words on the slide beyond the headline are kept to labels. The presenter's spoken explanation connects the two, which is where the detail that used to sit in bullets now lives.

Where it comes from

Michael Alley, an engineering professor at Penn State and author of The Craft of Scientific Presentations, developed the approach as an alternative to the default slide templates that push presenters toward topic headings and bullet lists, and has tested it with colleagues in classrooms and conference settings. The approach is closely associated with his work, though designers such as Nancy Duarte promote similar ideas: headlines that state the point and visuals that carry the evidence. The Penn State research page for the approach describes the core study, by Joanna Garner, Michael Alley, Keri Wolfe and Lauren Sawarynski, published in the International Journal of Engineering Education in 2013.

What the research found

In that study, two audiences learned the same technical subject by hearing exactly the same spoken words while viewing different slides. One set followed common practice, a topic phrase headline over a bulleted list; the other used assertion evidence slides. The assertion evidence audience understood and remembered the content better, and the difference was statistically significant. A further study by Shannon Aippersbach, Alley and Garner found that student presenters who built assertion evidence slides understood their own content better than those using the topic and subtopic approach, suggesting the method makes presenters think harder about what each slide claims.

How to write an assertion

State the finding, not the subject. Include a direction and, where possible, a number: suburbs with ten percent less canopy were 2.3 degrees hotter, rather than temperature and canopy cover. Keep it to two lines at a readable size. Then ask what the audience needs to see to believe it, and put only that on the slide. If no visual can support the claim, the slide may be making a claim that belongs in speech rather than on screen, or it may need a different kind of evidence, such as a photograph of the site or a simple diagram of the mechanism.

Common mistakes

The first is writing a sentence headline that is still a topic in disguise, such as this slide shows the results. A real assertion could be disputed; a disguised topic could not. The second is keeping the bullets underneath, which doubles the text rather than replacing it. The third is evidence that does not actually support the assertion, such as a general photograph behind a specific claim. The fourth is an assertion so long it wraps to four lines and becomes a paragraph. The fifth is using the format for slides that have no claim, such as a title or agenda slide, where a plain heading is fine.

Where it shows up in the product

Slide titles here are free text, so any template's headline can be written as an assertion, and chart, table, diagram and image slots supply the evidence. Charts come in 10 kinds and diagrams in 13, and chart templates like those in the example below carry a description line beside the chart, which suits a one sentence explanation of what the evidence shows. The thesis defence example on this site opens its motivation slide with a sentence claim about canopy and heat, and its results slides pair a chapter headline with a chart whose description states the statistic. A brief that asks for full sentence headlines and no bullet lists steers generation toward this style.

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