Back in March at the IA Summit in Vancouver, I presented "Bringing More Science to Persona Creation," which was essentially a preview of some of the ideas in the book, particularly the techniques for bringing quantitative data and statistical analysis into the persona creation process.
After the session, Christopher Fahey wrote an insightful post to his blog worrying that I was saying all personas should be more scientific. He's concerned that if personas require so much more work to create, people are less likely to bother creating and using them.
It's a valid concern, and my point was never that all personas need to have quantitative rigor. Like everything we do, we need to know our audience. If our audience will buy into personas created based on a few quick user interviews, great. Go for it. But if they will be skeptical that we are drawing important conclusions from so few data points, then quantitative research and analysis can be very successful. As personas become more popular, marketing departments are looking at them more closely and demanding that we apply the same rigor to our personas as they have applied for years to their segmentation models. Not all personas require this type of research, but tools are emerging for when we do need to kick it up a notch.
In many cases, ad hoc personas based on quick qualitative research (e.g., one-on-one interviews) are all we need.