It's the same as anything - how you look, your body language, the way you speak, the volume you speak at - it all matters and always will whether we like it or not.

In undergrad I did some retail electronics sales. When I first started if I didn't know the answer to something I would find out and be back to the customer within 30-60 seconds. That's all it took for them to not buy over and over.

Meanwhile, the best selling reps would say, "Absolutely!" to questions they had no idea what the answer was. Even if they were wrong the customer likely wouldn't come back and if they did they could usually be pacified enough.

Interesting lessons back then. I solved the problem by learning everything so I too could say, "Absolutely!" Took awhile though opposed to faking it.