When I design or evaluate interactive products and websites, I often use a framework I developed that I call E3T. E3T reminds me of four key dimensions that lead to a high quality user experience. The four dimensions are: engagement, ease of use, empowerment and trust.
Engagement is the willingness of the user to to interact with the product. Sometimes I think of it as "eyeballs on the page." It can be measured with simple metrics. One is time on the product. If the user is engaged, he or she will spend time interacting with the product. This is particularly useful for websites where you want to know if the user is engaged enough to spend time on the site or quickly abandons it. Another useful metric is frequency of return. If the user comes back to the product in the future, there is engagement.
Empowerment means that the user is able to get the desired result. A user always launches and application or goes to a web site because she has a goal in mind. It might just be amusement, researching a product prior to purchase, completing a transaction or conducting a complex business process. Whatever the goal, the question is "can the application or site deliver?" Can the user complete the on-line purchase? Can she set up a three-column view on the page? At core the issue of empowerment is whether the product does its job. A product that doesn’t deliver is useless.
Of course empowerment is more subtle and complex than I've laid out. It often not a black and white issue but a question of how well the application or site meets the user's goals. That's deeper than I can get into here but it should be clear that the more the empowerment the better the user experience. Knowing how to learn what the user needs and then implementing it so it works well -- that's the essence of good design.
Ease of use relates to the amount of effort that the user needs to put in to use the product. It's related to empowerment, of course, but asks the question "how hard is it to accomplish my goals." For example, if you want to cut your lawn, you can use either a hand mower or a powered mower. The hand mower takes a lot more effort so has less ease of use. Perhaps it's better exercise but that's another issue.
Effort is the amount of work that a user puts into Whenever a user interacts with a product he or she has some goal in mind. It may be as simple as entertainment (which is the case with a lot of web browsing and games) but there is often a specific end goal in mind – writing an email, making an on-line purchase, taking a photo and sharing it, or completing a business task. To complete the task, the user puts two kinds of effort into the process: effort directed at the substance of the task and effort directed at the UI. Effort directed at the UI is overhead. The lower it is the better. A product with a high level of ease of use means that most of the effort can go into the task and not the UI. That’s good for the user.
Trust is how confident the user is in the competence and integrity of the product and of the company behind it. Competence relates to whether the user can trust the product to deliver what it claims. If you save information will it really be available the next time you log on? If you cancel an order will your credit card be refunded?
Designing with E3T in mind makes it easy to make sure that you have touched on the key dimensions that underlie user satisfaction.