Saturday, September 13, 2008


At MLSS I've seen the spectrum of very good to very bad lectures. There seems to be a few rules that one could follow to avoid the pitfalls of the bad presentations. Such as,

Explain things through examples rather than cryptic mathematical definitions
Don't explain anything to complicated with your hands. Draw everything on a board.
Provide a motivation and backgorund on what you want to do.

Being a graphical models person I can't understand anything with out a graphical model anymore. It helps to specify the full bayesian inference scheme as the objective even if it is intractable. It helps orient people as a target for what you are trying to acheive. Many people explain non-probabalisitc methods without going through ths step. However, many of these methods have an implicit graphical model which be used to help orient people.

It is also good to use examples. People are very good at learning from examples. Once people understand something 90% it is then appropriate to supply a cryptic mathematic definition to completely disambiguate. For example, the DP is much more understandable with the stick breaking construction then the abstract definition. In physics thermodynamics is much easierto explain if you have one of those particle java applets that explains an ideal gas.

At one of the lecturers at MLSS I could look back in the audience and see that 95% of people where either surfing the internet, reading a book, or staring off into space. The lecturer seemed preety oblivious to it. Maybe he didn't even care. Many of us suspected he simply gave us a presentation he gave to his research group. He didn't take the time to make a new presentation even though his curent one was very innappropriate.

As for student presentations at the CBL, I've found there are a few reasons there are confusing:
1) the presenter doesn't really understand the topic themselves
2) Going over too much in too little time
3) language barrier

When niavely listenting to confusing presentations it seems like the person understands the topic so much no one else can understand at their level. However, in my experience, when you begin asking questions it becomes clear the presenting doesn't really understand the topic.

On the CBL wiki I've made a presentation guide with the following tips:

Technical Things

* Always label graph axis and be clear what graph represents.
o Use units if applicable (on graph axis and in general)
* Use page numbers on slides that show the current page number and total number of pages
* Don't forget your video adapter if you have a Mac. Mac folks always seem to forget this. Hugo has one in his desk that people can borrow.
* If your not presenting on your own computer then you should put the presentation in multiple formats: ppt, pdf, odf. Don't expect everyone else to have open office, for instance.
* Also, if not using your on own computer, make sure that the computer in the presentation has the necessary software for any demos. This includes Flash Player, Java applet support, any necessary video codecs, ect.
* Don't put too much text on a slide and keep fonts big enough

Before Starting the Talk

* think about, what kind of talk you want to give (rough idea of an algorithm, detailed description of sth, ...)
o depending on this you might not want to use too many equations (although the slides are not complete)
o keep it simple!
* give at least one test talk

Starting the Talk

* Might be best to start the presentation with material you expect most people already know. This allows you to synchronize that people are on the same page. Then start to introduce new things.
* It is good to establish the practical importance of whatever your presenting. Giving an example problem helps give people context. If everything is in the abstract then things become much more confusing.

During the Talk

* Always define what variables represent. maybe keep them on white board on the side.
o If necessary, define the dimensions of matrices and, if not obvious, the range of values variables can take (zero to one, positive, ...)
* If presenting a probabalistic model then put its graphical model, in Bishop notation, in your presentation.
* Give intuitive feel for all equations and variables to the extent possible
o Do this with examples and analogies
* Don't try to convey any important information with your hands alone.
o Never write out equations in the air with your hands (I've had a teacher who does this)
* Don't be afraid to write out and derive equations on the board
* In engineering problems it is always good to explain the input, output, and interface of any given system up front. If this is not clear people will get confused.
* If longer than an hour or so, give breaks for caffeine, snacks, etc.
* Don't rush through the slides. People should be able to read it! Explain, what's going on. Depending on your presentation style (more or less tutorial-like): 2-3 minutes per slide (in average) seems good


* Speak loudly, clearly, and not too fast
o Mumbling technical comments on the side only confuses people

Some Dos and Don'ts

* Don't point your laser pointer at people. It always seems kind of awkward.
* Don't point with hands. People can't see what your pointing at exactly. Use the laser pointer.
* Don't point to everything with the laser pointer.
* Do look at the audience
* Do modulate your voice and be interested in your own stuff. It's not trivial to most others!
* Do use examples and demos
o In intro physics they always like to use those Java applets of a spring oscillator and so on. Try to do the same if possible/applicable.

After the Talk

* Post your slides on the Presentation Archive
* Use our template if you can get Latex to work


* some hints if you give a short talk
* All the stuff in this guide to Terrible Presentations (…and how to not give one)

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