Is it good to have slides that may be skipped during a presentation?

I am preparing a seminar talk. Currently the presentation contains some theorems and some proofs. Probably, I will not have time to explain all the proofs - I will have to skip some of them. My question is, which of the two options is better:

Keep the slides with the proofs visible, and during the presentation, if I see that the time is tight, rush through them saying that "I skip the proof", or -

Keep the slides with the proofs hidden, and during the presentation, if I see that there is enough time, unhide and go through them?

The advantage of option 1 is that the audience sees that I have a proof and they can read it later if they want; also, if I have time it is easier to present the proof;
the disadvantage is that it might look confusing or unprofessional to rush through slides. Are there other considerations?

10 Answers
10

Put the slides that contain the proofs after the last slide and have links on the relevant slides so you can jump to the proof slide and back to the next one.

That way no-one will know if you skip the proofs, but they could see you click the link to jump to a proof if you have the time.

I use a 2D layout for that.

I do not know the software you will be using, with reveal.js you can have a linear progression, and some slides can go "down" (these are the detailed ones).

reveal.js

This way I get to keep the continuity of the presentation, and move deeper if needed.

While I love the answer from Solar Mike and the comment from GEdgar, I'd like to offer an alternative that has sometimes worked well for me:

Occasionally I elect to present a very rough sketch of a proof on my slides--this allows me to show that the proof exists and give some sense of the tools required without getting mired in the intimate details of the argument or burying my audience in a hail of notation. Depending on how time is running I can either breeze through this sketch quickly or more slowly fill in some of the details and intuition verbally (though I would highly recommend against attempting to present a full proof in this way). In addition, I can also mention that I would be happy to provide the full proof to anyone who would like to see it.

Keep the slides with the proofs visible and explain -- upon reaching the first proof -- that you've included proofs for those that like to read ahead and you won't have time to go through them/all of them.

Response to DVSA:

That's terrible advice imo...there shouldn't be anything
on the slides you aren't talking about...skipping the proof [looks] unprepared...

For every speaker there exists an audience member that is unengaged, because they've already understood the material. That audience member can engage themselves with the proof. By explaining, "I'll explain the general idea of the theorem; the proofs are included for those that like to read such details," your criticisms don't apply. This strategy will be appreciated by some often neglected members of the audience.

Don't ever say during your presentation, "because we're short on time, we're going to skip these next slides". That just highlights your failure to prepare a talk that is of the appropriate length, and annoys the audience by teasing them with content that they will not get a chance to see.

If you must prepare some extra slides, either because you don't know in advance how much time you will get, or how many questions the audience will ask, or how interested the audience will be in the technical details, then do it as professionally and seamlessly as possible.

One way is to use Keynote, in which case you can use an iPhone as a remote to control the slides. The iPhone will display a thumbnail of each slide, which lets you select the slide you want to advance to, and the audience will never know that you skipped anything.

Alternatively, set up the computer such that the external display is not a mirror of the laptop's screen. That could also let you select the slide from your computer without letting the audience see your supplementary materials.

Depends on the size of the audience and/or your ability to “read” them. You figure out in advance what to minimize if you sense they are following well or even bored; and what additional detail to go into if you sense they need it.

The most frequent reason I see for speakers skipping slides is that they were interrupted by questions and were suddenly under time pressure.

Of course, one can naively say "don't accept questions". Stuff happens. If an interviewee for a slot refuses to take an important question, that's it for the candidate, and they may as well stop. You may have a poor session chair that loses control. Again, stuff happens. If you insist, under such cases, to stick rigorously to your stack, you're being rude to other in the session, or you look unaware of the situation.

The best speakers need to be able to think on their feet.

As an addition to the existing answers, if there are slides that you visibly skip over, you should explain why you're doing that. From personal experience, if the audience thinks you're trying to hide something, the whole atmosphere of the presentation can become antagonistic.

Some softwares have been suggested to help you skip slides without the audience noticing. I have two options for you in this regard, one is https://prezi.com/ which I have used a fair bit. It allows you to move in any direction between your 'slides' and the other, assuming you are working in PP, is to use 'action' buttons as links to other locations in your presentation (under links tab).

The drawback with both is that you need a thorough knowledge of your presentation, inside, out, back and forwards, as this is how you will be able to move through it!

Some people have complained that the transitions in prezi, very forwards/backwards and fluid, leave them feeling a little sea sick from watching.

Overall, its not a problem to skip slides as long as you cover all the evidence in different ways, such as talking ad-lib with another slide if its appropriate. There is no point in making people suffer the same information twice as that leads to the well known phenomenon of 'death by powerpoint'...

I wouldn't do this in a professional business environment, but for academia it's no big deal to skip slides.

For a seminar talk you will probably have differently formatted handouts, but in any other case it's common to hand out the slides and so they should be linear structured, not 2d or having half of the content in the appendix.

Sure you could try to estimate exactly what you will be able to present in the timeframe, but actually you can't. Your audience should learn something and so they should ask questions if they don't understand something. And based on how many questions there are you will not get anywhere near what you estimated.

I think the ability to adapt your talk to the audience to enable them to get the most out of your talk is far more important than to have a smooth, perfectly planned out show. On the other hand it's more likely that nobody asks questions, only very few can follow up to the last slide, but everybody sits there quite and politely. But that's not how it should be.

The difference to business scenarios is, that it's far more involving for the audience to understand proofs, than to grasp some facts about products and bar charts. And your not trying to sell anything so you don't have to keep a polished facade that might deteriorate by skipping around your slides.

Thank you for your interest in this question.
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