When should you give an overview presentation?

Is it better to give a broad (wide) or a deep (narrow) presentation? Should you try to cover a lot of material (overview) without much detail, or just one topic in excruciating detail? I think the answer depends both on the audience and the presenter.

On October 29th in her Speaking About Presenting blog Olivia Mitchell discussed 6 Reasons You Shouldn’t Give an Overview Presentation, which were:

1. It’s not memorable
2. Nothing will stand out
3. Positions you as a generalist
4. It’s uninspiring
5. It’s boring
6. It’s not efficient

She referred to a 2008 post by Garr Reynolds, Deep or wide? You decide. Mr. Reynolds in turn referred to Michael Ally’s book, The Craft of Scientific Presentations. Both posts showed graphics like the left and center boxes shown above. Olivia also referred to a November 2009 post by Jon Thomas, The Advantage of Depth Instead of Width in a Presentation.

On page 63 of The Craft of Scientific Presentations Michael Alley says that:

“Just because giving a ‘broad-scope’ presentation is difficult does not mean that one should avoid giving such presentations. Rather, giving a broad-scope presentation means that the challenge is greater and the speaker has to think long and hard about the presentation’s structure.”

An old psychology (or philosophy) joke says that the whole world is divided into two types of people: those who divide things into two groups, and those who don’t. I am one of the second type of people. I think it is possible to give an “L-shaped” presentation that starts by explaining one key point in depth, and then continues more broadly (as shown above at the right).

For example, back in January at the SIEO-NACE Sun Valley Symposium I gave a 45-minute presentation that was an Introduction to Stainless Steels and Corrosion. It was divided into three sections:

1. Passive Film and Processing (21 slides)
2. Types and Typical Compositions (10 slides)
3. Corrosion - Pitting, Crevice, and Stress Corrosion Cracking (16 slides)

My first section had the key point, how stainless steels work. The surface of a stainless steel reacts with oxygen to form an extremely thin, self-healing, chromium-rich passive film which stops further corrosion. This process is called passivation, and the invisible film is only 10 to 100 atoms thick. When you understand how thin the film is, then you can understand why the surface must be processed meticulously to remove contaminants from fabrication. I spent over 40% of my time on that first section. The slide sequence I used was discussed in a January 12th blog post on How Thin is Extremely Thin?

I think you can and should give an overview presentation when you really know both your audience and your topic. It is not easy, but it is rewarding. Previously I had attended two other Sun Valley symposia, so I knew that an in-depth presentation would not really be appropriate. Another speaker had cancelled in mid-December. I had just three weeks to prepare as a fill-in. The talk was a celebration of my 30th anniversary as a NACE member. By the way, I'm sure I read Jon Thomas's post before I started planning.