A presentation is not a "how to" manual

I can't tell you how many presentations I've seen where a speaker will describe a product (often a new web application) and then show multiple slides giving a detailed explanation of how to use the related website. Presentation slides are not a good way to tell the audience to "click" at the top vs. the bottom of a web page, or for that matter to walk through any type of detailed "how to" instructions.

A presentation might motivate your audience to go to you website, but it is not a good tool for teaching them how to use it. Use your time to inspire your audience about the product and get them to open the relevant webpage, but don't try to give them detailed user instructions. It simply doesn't work.

If your goal is really to teach people how to use your website, then be sure they bring their laptops to the meeting and have them "click" through things in an active mode. Give them a problem to negotiate rather than blathering on with slides.

I attend a lot of presentations where an administrator describes a new web tool (HR, finance, facilities management, that kind of thing). It's usually a 25 slide presentation with lots of detail about the associated website. They would be much better giving a 3 slide presentation, having the audience turn to the website, and then have the audience use the website to solve a hypothetical problem while the speaker can answer questions.

Don't use slides to teach a class

The other day I attended a course on diagnostic technologies. The subject of the day was the mathematics of test validity. It involved variables such as false positive rate, false negative rate, disease prevalence in the population, number of subjects in a trial, etc. The instructor taught the course with PowerPoint slides.

While there are numerous statistical subtleties in interpreting data, the basic mathematics involves no more than a bit of first year calculus. Nevertheless it was confusing. Unless a student is writing down the mathematics as it is presented, he/she will not absorb it. Slides allow an instructor to present information too quickly. It's hard to absorb the meaning of equations as a passive listener.

In the old days, a science lecture would unfold on the chalk board in a step by step manner. This gave the student time to absorb the material and reinforce the learning process by taking notes as the instructor wrote on the board. There was a deeper connection between speaker and listener.

Slides are great for presenting a broad picture of research that has an interesting narrative. They are a poor way to ingrain mathematics or a scientific theory in a student's head. A slide presentation is better at inspiring interest than it is at teaching methodology.

Two simple questions we should ask ourselves before giving a presentation

You're about to give a presentation to a scientific audience. Before you do, ask yourself:

1) What do I hope to achieve by giving a presentation?

2) What can I realistically achieve?

I typically proceed my own "how to do a scientific presentation" presentation by tossing these questions out to the audience. I usually get blank looks, as if no one ever thought about such questions. Too many scientists simply "grab their slides," without establishing goals for their presentation.

Eventually someone in the audience will say, "I want to explain my science." Fair enough, but this gives rise to other questions. To whom do you want to explain your science? Scientists in your specific subdiscipline? Scientists in related disciplines? Scientists in different disciplines who may have methods and technologies relevant to your work? A more general scientific audience? Have you altered your slides and your spoken narrative to target the audience you care about?

A second related question involves the depth of your explanations. Realistically, nobody is going to remember your slides 24 hours after the talk. Even experts in your sub-discipline will have trouble as you rush through dozens of detailed slides in a futile effort to communicate a comprehensive and detailed review of all your work.

Slide presentations are not the place to "prove" results or give overly detailed reviews. A slide presentation is an opportunity to inspire your audience, motivate new collaborations, get other scientists to follow up with questions and perhaps get them to read your journal articles. Presentations are a great place to motivate thoughts about how your work relates to other ongoing research. These are realistic expectations for what you can achieve. Detailed "proof" is best left to journal articles and efforts to replicate results.