There are far more users for your application than you can possibly design for. Alan Cooper has some advice on how to pick the ones that will let you deliver the right UX for everyone.
Most applications will have a wide variety of users. In UX design, we assume that we can group those users into groups whose members are similar enough to count as one person (in Learning Tree’s UX design course we call those groups “cohorts” and the person who represents the group is called a “persona”). The reality is that your application can deliver an effective UX for, at most, five personas — and three personas is probably a more reasonable target. The problem is that your application probably has far more than five cohorts/personas which raises the question: “How do you pick which personas to design for?”
The trick is to decide what are your “critical” cohorts: The cohorts that will make the difference between a successful and an unsuccessful UX for your users. I always say that you should start by designing for the persona representing the cohort that has the biggest input to your appraisal. Amazingly, many people feel that isn’t necessarily the optimal criteria.
The obvious cohort is the one that represents the largest body of users. The corollary would be to ignore the cohorts that represents the smallest number of users. That’s obvious…but not necessarily right. Much depends, for example, on what contribution those smaller cohorts make to the organization or how much trouble those smaller cohorts create.
For example, in a profit-based company, I’d be inclined to pick the cohort that makes the biggest contribution to the company’s profits, regardless of that cohort’s size (or, possibly, I might pick the cohort with the biggest contribution to company profits per cohort member). In a government or other service-based organization, I’d be inclined to look at the clients who take the most time to handle (the idea being that, by freeing up time from these people, the organization gains more time to handle many more less labor-intensive clients).
Another issue to consider is “coverage,” which cohorts, if you make them happy, will automatically provide a satisfactory UX for other personas?
Those choices are summed up in what Alan Cooper (the father of modern UX design) calls the “primary persona”: the persona who must be satisfied but who will not be satisfied with an interface designed for any other persona. The primary persona is someone whose needs are not covered by meeting the needs of any other persona. What’s interesting about the primary persona is that supporting that persona will often cover the needs of other personas.
As an example, when designing the P@ssport in-flight entertainment system, Cooper’s company settled on four personas:
The two business travelers provided coverage for a wide variety of other personas because the business travelers represented contemporary users with a typical amount of knowledge about computer interfaces and contemporary entertainment. Clevis, on the other hand, did not represent any other cohort. Moreover, Clevis hardly represented a sizable portion of airline customers.
Nonetheless, Cooper’s team decided that Clevis was the ‘primary persona’ because any interface tailored for the other personas — all of whom were relatively computer-savvy — wouldn’t be acceptable to Clevis who wasn’t. On the other hand, an interface acceptable to Clevis would probably be acceptable to the other personas: people who were computer savvy could work with a UI designed for someone who wasn’t computer savvy. Effectively, Clevis provided coverage for the other personas. Since the two business travelers covered off many other travelers, delivering an acceptable UX for Clevis would probably provide an acceptable UX for everyone (and, if you threw in some obscure shortcuts for the 9 year old boy to exploit, you’d probably make him happy, also).
In the end, by targeting Clevis, Cooper delivered a UX that ended up being used by literally millions of airplane passengers.
And, by the way, I suspect that there was another reason for including the nine year old boy: When a nine year old boy on a plane is unhappy, I bet everyone is unhappy — especially the flight attendants. It seems to me that’s also a good reason for picking a persona: Making life easier for the company’s employees. And I bet those employees have input to your appraisal.