"This issue should be tested in a usability lab with a reasonable cross section of the target market" That's the thing. It was. And it works for everyone I've

"This issue should be tested in a usability lab with a reasonable cross section of the target market" That's the thing. It was. And it works for everyone I've ever met, including my wife and my parents who are the polar opposite of 'technical'. I'm not making baseless claims of the user being [insert one of the choices], it was based on my (rather extensive) experience with the device and users of it.