# 科学网How to give talks (2)

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My recent attendance at meetings in Xian and HongKong, allowed me to listen to many interesting talks and good presentations. As a student of giving talks and advice giver for making presentations, I am moved to make some observations on delivering talks.

People have caught onto the use of animation in PowerPoint slides. Many such use are impressive and effective. The general level of presentations have definitely improved in recent years. What I mentioned below are another set of details speaker and slide preparer should paid attention to so that they further enhance their effort.

1. Many speaker still put far more information and content on each slides with the result that they don't have time to explain all the stuff on the slide and cause only distractions. In fact, if you don't have time to explain what you put on a slide then the information should not be there on the slide! Put everything you can think of on a slide may sooth your conscience of being complete but you achieve the exact opposite result of confusing the audience. One should use this criterion as a test when you rehearse your talk. A necessary but not sufficient condition for a good talk is to be able to explain everything on the slides in the allotted time. I have said this before. Your job giving a talk is NOT to satisfy yourself but to make your talk interesting and understandable to the audience. There is no need to say everything you know in a talk.

2. Every math symbol, equation, and graphics you introduce in a slide of you talk should always be done BECAUSE you need to use them repeatedly. Not only this reinforces the shorthand notation but also minimizes content of a slide and explanation required. Otherwise there are no reason for their use except adding more confusion. Using symbols and equations may be rigorous and precise but unless done carefully their use only adds confusion. **Your job is to be conceptually and logically rigorous in giving a talk but NOT mathematically rigorous**. These two views of being faithful to your audience should not be confused. In fact, I'd argue that using too much mathematics in your talk is actually cowardly and taking the easy way out. Being understandable and conceptually faithful at the same time are much more difficult. But the effort is well worthwhile and will pay off for you in unexpected ways years into the future.

3. The purpose of a math symbol in lectures and writing is a SHORTHAND. When you have to express a concept or an idea REPEATEDLY, you use a symbol or a string of symbols (I.e. An equation) to save time/ words and to be precise provided the symbols have been defined previously. In a lecture it is difficult for the audience to remember many definitions once they have been introduced. Thus use symbols very SPARINGLY and ONLY when you are convinced that you will need them many times in the course of your lecture so that you can reinforce the definition and concepts.

4. The idea of careful use and reinforcement of symbols apply even more to graphics and animation. Yes, a picture is worth a thousand words. A carefully designed graphics reused several times in a talk with different detail animation or data can tell ten thousand words. That is taking the art of presentation to a new higher level.

Thus, in summary here, in my opinion, is a checklist for every prepared presentation:

1. Make sure you can explain EVERYTHING you put on a slide in the time allotted . In general use no more than two minutes per slide => about 15 slides for a 30 minute talk.

2. Use symbols, equations and graphics only when you are convinced that you will use them repeatedly in your talk. They need to be reinforced.

3. Prepared your talk from the viewpoint of the audience. Think how they would like things explained to them.

4. You should always start preparing and rehearsing your talk weeks in adavance. Improve and memorizing it to the point that you only need the PowePoint slides to help you deliver the talk.

5. Go over my previous article on "how to give talks " for more tips.

During the IAS workshop of CUHK and the CASE 2017 conference which I mentioned in previous blog articles , , there was one such talk which observed all these rules and perfectly delivered. It is the presentation by Professor Lucy Pao of University of Colorado. I have urged her to make a video tape of this 30 minute talk on wind and solar power for electric utility. The talk is not only informative for anyone interested in the subject but also a good teaching tool for giving good talks.

I shall give the link as soon as this is available.