In that case, a confounding factor is that the people in the club may be able to tell the difference between the outfits. So it isn't just the second man's conf

In that case, a confounding factor is that the people in the club may be able to tell the difference between the outfits. So it isn't just the second man's confidence, it's that the people there know he's willing to blow a lot of money on looks. That may conceivably affect their reactions regardless of the man's confidence.