Acting with certainty, even when you're not 100% sure, makes you more right even when you're wrong.

How is that?
Certainty, something to believe in, is a basic human need. Children get that certainty from their parents. As we grow into adults, that need doesn't disappear. A few people develop this trait within and of themselves. Most people seek it from others.

When you carry yourself as if you know exactly what will happen, what the correct answer is, where to go next -- you'll cultivate a following even when you have no idea what you're doing.
Just like the commercial, you're not really a doctor, but you can play one on TV.