Consider a health information site with two sets of fact sheets: A simplified version for the lay audience and a technical version for physicians. During testing, a physician participant reading the technical version stopped to say, “Look. I have five minutes in between patients to get the gist of this information. I’m not conducting research on the topic, I just want to learn enough to talk to my patients about it. If I can’t figure it out quickly, I can’t use it.” We’d made some incorrect assumptions about each audience’s needs and we would have missed this important revelation had we not tested the content.