Master the Art of Evidence-Based Speaking

A confident voice can make almost anything sound true. Unfortunately, your audience is allowed to and will ask questions.

You can say, “Social media is destroying our attention spans,” with perfect eye contact, dramatic pauses, and the conviction of someone delivering the State of the Union, but eventually, one question ruins everything: according to whom?

That’s where evidence comes in.

Evidence is what turns an interesting thought into a believable argument. It gives your audience a reason to trust that your claim exists outside your own head. But using evidence well is its own balancing act. Too little, and your argument feels hollow. Too much, and suddenly your speech sounds more like a stats dump. Let's see it in action by exploring the Goldilocks Principle of Evidence.

The Goldilocks Principle of Evidence

Too Little: The most popular sport in the world is soccer which has the most fans around the globe.

Here's the thing: most popular already implies that soccer has the most fans around the globe, so you're not really proving anything. Also, what other information are you adding beyond what is common knowledge?

Too Much: With over 4B fans, or approximately 49% of the world population, soccer is the most popular spectator sport with four major tournaments, with 14 million Americans playing outdoor soccer in 2023.

The problem here is that this stats dump confuses rather than clarifies. If I asked you to share your takeaways after reading this, I'm sure your mind would feel like a blizzard.

Just Right: According to Yahoo, soccer has over four billion fans, making it the most popular sport in the world.

Perfect! One clear stat with evidence!

Research Tips for Speakers

1. Use credible sources (universities, established newspapers, and research institutions(

2. Find statistics over opinions (numbers convince better than someone's personal view)

3. One powerful stat beats ten weak ones (don't overload your audience)

4. Always cite your sources (it builds your credibility (ethos))

5. Don't cite sources for everything. (we know Tokyo is the capital of Japan, don't need a source for that one)

Quick Evidence Drill

Every time you write a factual claim in your speech, ask yourself three questions:

• Says who? Do I have a credible source?

• So what?Have I explained why this evidence matters?

• Why this stat?Is this the strongest piece of evidence I could use, or did I include it just because the number sounded impressive?

If you can answer all three, your evidence is probably doing its job. Because research shouldn’t make your audience think, Wow, they opened a lot of tabs. It should make them think, Okay. I believe them.