According to Michael Wolfe in “Conclude with the conclusions”, a letter to the editor on pages 6-7 of CACM, 53(11), Nov. 2010
[…] “Presenting Your Project” […] made several debatable points about presentations, one of which was inexcusable: “…I always end with a Questions slide.”
You have just given a 25-minute technical presentation […] Your penultimate slide summarizes the whole presentation, including its “takeaway” message—everything you want your listeners to remember. Now you expect to spend four or five minutes answering questions. The slide you show as you answer will be on screen two or three times longer than any other slide.
So why remove the most useful slide in the whole presentation—the summary—and replace it with a content-free alternative showing perhaps a word or two? […]
My advice: Remove the “Thank You” and “Questions” slides, and leave up your “Conclusions” and “Summary” as long as possible.
More presentation advice, according to Jerry Weissman
Vinod Khosla’s five-second rule: he puts a slide on a screen, removes it after five seconds, and then asks the viewer to describe the slide. A dense slide fails the test—and fails to provide the basic function of any visual: to aid the presentation.
By applying his simple rule, Mr. Khosla is addressing two of the most important elements in presentation graphics: Less is More, a plea all too often sounded by helpless audiences to hapless presenters; and more important, the human perception factor. Whenever an image appears on any screen, the eyes of every member of every audience reflexively move to the screen to process the new image. The denser the image, the more processing the audiences need. At that very moment, they stop listening to the presenter. Nevertheless, most presenters continue speaking, further compounding the processing task. As a result, the audience shuts down. Game over.