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  • Gavin McMahon

Showing Evidence — How to boost your credibility.



My work is about how to think clearly and deeply,

using evidence, and all that has to pass through some presentation state.

Edward Tufte


A tractor salesman visits a farmer and asks, "Can I show you my new tractor?" “Sure, go on then,” replies the farmer. The salesman jumps in the driver’s seat and starts the engine. He then plows three fields, pulls stubborn tree stumps, and bales a ton of hay, all in record time. “Well, what do you think?” asks the salesman, jumping off the tractor. The farmer replies, “Sure, it’s all very well in practice, but what’s it like in theory?”¹


Like most of my jokes, I inherited this one from my father. It’s not that funny, but it makes a point.


When you’re presenting, persuading, or selling, you are trying to convince people. To get them to understand, engage, and remember. More than that, you are often dealing with the curse of knowledge. You know a lot about your subject; your audience doesn't and isn't very interested. You have to present evidence.


Michael Alley, Engineering Professor at Penn State, uses the Assertion-Evidence model.² According to Alley, it “leads to better comprehension and recall by the audience.” In PowerPoint, it is a proven technique to put a point across on a slide. Alley’s research found that a compelling, crisp headline in sentence form, backed up by evidence (usually visual), increases comprehension and recall by up to 18%. This brings us to the question – is some evidence better than others? What type of evidence works best to build credibility? How do you show proof? How do you build evidence into your story?


The evidence stack.

The evidence stack is the brainchild of Simon Levin and Joel Wecksell. Both former Gartner analysts, they now advise technology companies on how to position their products to advisory firms like Gartner and Forrester.


“Analysts are taught to never assess a company by what they say they are doing, or what they say they will do, but by proof of what they are doing and proof of what they have done. That’s where the layers of evidence come in,” says Levin. It’s the distinction between claim and proof that’s important, and how credible the evidence is along the way.


Let’s look at the stack — from the bottom (weakest) to top (strongest).


The claim, with a little hyperbole.

This is the bottom of the stack. It’s the assertion part of Alley’s Assertion-Evidence model. On a slide, it could be the headline. On a web landing page, it might be the central strapline. They are usually unsubstantiated. They’re not much better than, “now with 50% more magical ingredients!” But it’s important to make a claim. In fact, it’s essential — but be aware that you need to add evidence. For example, Intercom’s “The #1 Business Messenger.” Or Respond.io claiming it is “The #1 Business Messaging Platform.” Both set out what they’re about. But can they both be right? After the claim, we have to start to add evidence. And as you will see, the more concrete and visceral the evidence is, the better.

The more you can show evidence, the better a presenter you will be.


Blinding with science.

Unfortunately, this is the default setting of a lot of us. Even marketers, product managers, and sales professionals fall victim. A lot of our decks become stuffed with techno-babble, acronyms, and terms of art. We make a claim, for example, Acquaform — the world's best skin cream.³ We then add some hyperbole — watch fine lines and wrinkles vanish overnight. And then, because subconsciously we know we need to back that up — we blind with science. This involves a smidgen of jargon and a touch of mumbo-jumbo. Enough to sound impressive, but to the discerning observer, not exactly proof.


Acquaform. The world's best skin cream, now with Retijuve™ and organic Acacia Extract. Watch fine lines and wrinkles vanish overnight.


You will see slide decks stuffed with this. It gives the presenter the warm, fuzzy feeling of conveying 'useful' information.


Reactive Microservices Architecture on AWS⁴

For example, you may be selling technology to a CIO. The assertion — a complete set of infrastructure and application services that enable you to run everything in the cloud. Your evidence — an architecture diagram with terms like ‘3-tier service-oriented architecture’. Throw in ‘enterprise-grade,’ ‘edge nodes,’ and ‘leverage multiple IP addresses to implement a virtual IP (VIP) address.’ Talk about ‘high availability failover solution,’ and my head starts to spin.⁵


Demonstrate know-how.

Albert Einstein famously said, “If you can’t explain it simply, you don’t understand it well enough.” That’s a lesson that business tends to ignore. Blinding people with science and marketing hyperbole are standard ways of speaking. It’s the language of our tribe. Thankfully, speaking simply and demonstrating know-how is on the rise. It explains the growth of Corporate Storytelling, Infographics, and Explainer Videos. Many companies have made good use of them, explaining products and building brands. There is a human reaction to simple explanations. Simply put, we’re more likely to believe them. In recent studies, Occam’s razor — the simpler explanation is the better one — is proving out. We have a cognitive bias to prefer simpler, more common sense explanations.⁶ ⁷


Credibility, bought and borrowed.

Moving up the stack, we come to the idea of using others’ credibility and bathing in its halo. Think of it as the positive version of guilt by association. Let’s assume you’ve made your claim. You can describe it in a few choice words, and you’re keeping the techno-babble in your back pocket. You can explain your point simply, in a way that would make Einstein proud and Occam jealous. But you’re still stuck in the realm of theory and have no proof. What to do? In the absence of hard proof, borrow some credibility.


Beyond Meat and Impossible Foods are, in effect, borrowing credibility. It’s in the name, by attaching to the word burger — Beyond Burger and Impossible Burger. This raises a beef with the National Cattlemen’s Association.⁸ They argue that plant based meat substitutes are not meat. So they should not use language associated with meat. Their fear is real. They see bankruptcies in the dairy industry. Where almond milk consumption increases,⁹ and dairy milk declines.¹⁰

Stripe, the fintech payments platform, borrowed credibility to power their success. In 2010, they were an unknown, angel backed startup. Today, Stripe values at $36B. ¹¹ Their ingredients? Obsessive customer focus, a clever distribution model, and transparent pricing.¹² Another magical ingredient — borrowed credibility. Imagine how much easier it is to trust an unknown brand when you see billion dollar¹³, household names listed next to it.


Credibility, given.

Jumping a couple of spots up the Evidence Stack is another type of credibility. The more polished, sensible cousin of borrowed credibility, given credibility. This is a customer testimonial, or a case study. It’s a spot in a Gartner Magic Quadrant or Forrester Wave. This is validation from a neutral third party — a research firm.


Presenting Data.

Further up the stack still, we begin to get to real evidence, in the form of data. Much can be implied by a single data point, which can be good for the presenter. Ideally, this data is visualized to be a clear, readable chart, and make a compelling point. This point is a beat in your story. A pivot on which an argument turns. Make sure the source is credible. That in itself carries credibility. The Economist is more reliable than FunTrivia.com.


Of course, not all data is equal. It is certainly not displayed equally. You must display your data to tell a story. It must have a clear, compelling insight. It must be easy to read, and accurate. There are basic rules of presenting data, when followed, that will help. Ignore those rules at your peril. it quickly descends down the evidence stack. You use your data to blind people with science.



Develop an eye for data. Look at what others are doing. Here’s a listing of professionally designed data visualizations that hit the mark.



Demonstrate and use.

Back to the tractor, the very best way to back up your assertion is proof that it works. Putting something in people’s hands, giving them a real experience is the best source of evidence. It makes it real, and it makes what you’re talking about come alive. In silicon valley folklore, Bill Gates demod an early version of Windows to investors. He did it by showing them a Mac and saying, "it will be like this."¹⁴


In this story, Gates previewed a paper prototype. A demonstration of what Windows would look like, without actually building it. That's the least plausible way to demo, but it can be very effective. Better still is a canned demonstration. You have working code, or parts working, but it's not quite ready for prime time. Here, you are demonstrating how it will work, what it will look like, and that it can work.


Next up is a full trial. Don’t underestimate the power of touch. It’s defined retail experience since the days of Harry Selfridge. Being able to touch and play with stuff makes it feel more valuable. A recent study¹⁵ showed the longer you touch an object, the greater the value you assign to it.



How can you use the evidence stack?

The evidence stack is an incredibly useful ‘how-to’ tool. Not only do we teach it, we use it all the time. It’s a practical way to make sure that the business story you are telling comes off as credible.


Next time you’re building a presentation — a board meeting, an important sales call, a product update — look at your slides. Ask yourself two questions:

  1. Does the slide show evidence?

  2. Where is that evidence on the stack?

If our experience is a guide, you will find most of the slides wander between claim and blinding with science. Turn those, at least into demonstrate know-how, by ruthlessly simplifying them. Look at where you can borrow credibility. Pay attention to your data. Is it presenting beautiful evidence, or is it blinding people with science. And lastly, think about how you can create an experience. How can you get this in people’s hands?



Gavin McMahon is a founder and Chief Content Officer for fassforward consulting group. He leads the design and product development of fassforward’s services. This crosses diverse topics, including Leadership, culture, decision-making, information design, storytelling, and learning design.

Eugene Yoon is a graphic designer and illustrator at fassforward. She is a crafter of Visual Logic.

Eugene is multifaceted and works on various types of projects, including but not limited to product design, UX and web design, data visualization, print design, advertising, and presentation design.


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