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.

How to design a poster

Many of the tips and the overall philosophy on this blog are relevant to designing a poster.

The first thing is to consider the audience for your poster. Do you expect someone to read the poster while you're not there, or do you want to use the poster to support your oral presentation? To me the answer is obvious and it is the latter. Most poster observers are walking around, they don't want to stand there for 20 minutes reading alone, and they want to be guided through the substance quickly. Moreover, you can always have a handout with more detail

Like a slide presentation, don't use a poster to replace your journal article.

Below is an example of a 36" x 48" poster that supports my activities on this website (it might be too small to read as reproduced here, but you get the idea). I've limited myself to 9 fairly simple visuals and provided enough simple text to help me talk a listener through the content and even to help a viewer if I'm not there. Just like preparing a presentation, you need to think through the key summary points and not overwhelm the audience with detail. Exclude all graphics that you don't plan to talk about. Be sure you can talk through the poster in 5 minutes, 10 at the outside. Remember, the idea is to get people interested in your work, not to give a comprehensive review. Show the most important results on easy to understand graphics.

My presentation first walks the listener down the left most (blue) column, summarizing the problem statement, the overarching question, and the overarching solution. The top gray horizontal bar provides more detail about the challenges, while the tan box provides two examples of converting bad slides into good ones.

I can get through this in about 5-10 minutes. If the listener is interested, I will direct them to more detailed information.

Keep your poster simple and clean. An alternative to the above format is to have the poster center on a single overall "systems" diagram of your research (see October 15, 2015 "tip"). A single central figure can be a great device for a poster if you can use it to talk through the essence of your research.

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.