How to evaluate the design?

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In many ways, the most creative, challenging, and under-appreciated aspect of interaction design is evaluating designs with people.

The insights, that you’ll get from testing designs with people, can help you get new ideas, make changes, decide wisely, and fix bugs. One of the reasons why a design is such an interesting field is its relationship to truth and objectivity.

Design can say more in response to a questions like: How can we measure success? Is it just personal preference, or, a little bit more? At the same time, the answers are more complex, and more open-ended, and more subjective, and require more wisdom, than just a number.

There are different kinds of knowledge that you can get out of different kinds of methods.

Why evaluate designs with people? Why learn about how people use an interactive system? One major reason for this is that it can be difficult to tell how good a user interface is until you’ve tried it out with actual users.

That’s because clients, designers, and developers may know too much about the domain and the user interface. Or have acquired blinders through designing and building the user interface.

At the same time, they may not know enough about the users’ actual tasks. And while experience, in theory, can help, it can still be hard to predict what real users will actually do.

You might want to know how can people figure out how to use it? Or do they swear or giggle when using this interface? How does this design compare to that design? And if we change the user interface, how does that change people’s behavior? What new practices might emerge? How do things change over time? These are all great questions to ask about an interface, and each will come from different methods.

The value of having a broad toolbox of different methods can be especially valuable in emerging areas like mobile and social software. There people’s use practices can be particularly context dependent and evolve significantly over time in response to how other people use software through network effects and things like that.

Usability studies

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One way to learn about the user experience of a design is to bring people into your office and have them try it out.

A basic strategy for a traditional user-centered design is to iteratively bring people into your office until you run out of time and then release. And if you had deep pockets, these rooms could have a one-way glass mirror and the development team can be on the other side.

In a cleaner environment, this may be just bringing people into your dorm room or office. You’ll learn a huge amount by doing this. You can watch somebody uses a new interactive system and learn something.

As designers, we get blinders to systems’ quirks, bugs, and false assumptions. However, there are some major shortcomings with this approach.

In particular, the setting probably isn’t very ecologically valid.

First — in the real world, people may have different tasks, goals, motivations, and physical settings than in your office. This can be especially true for interfaces that you think people might use on the go, like at a bus stop or while waiting in line.

Second, there can be a please-thee experimenter bias, where, when you bring somebody in to try to use your interface, they know that they’re trying out the technology that you developed. And so they work harder or be nicer than they would if they had to use it without the constraints of a lab setup with the person who developed it watching right over them.

Third, in its most basic form, where you’re trying out just one user interface, there’s no comparison point. So while you can track when people laugh, or swear, or smile with joy, you won’t know whether they would have laughed more, or sworn less, or smiled more if you’d had a different user interface.

And finally, it requires bringing people to your physical location. This is often a lot easier than people think but it can be a psychological burden, even if nothing else.


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A very different way of getting feedback from people is to use a survey.

Surveys are great because you can quickly get feedback from a large number of responses, and it’s relatively easy to compare them all to alternatives. You can also automatically tally the results. You don’t even need to build anything, you can just show screenshots or mockups.

One of the things only appears — it is usually a difference between what people say they’re gonna do, and what they actually do.

Ask people how often they exercise, and you’ll probably get a much more optimistic answer than how often they really do exercise. Still, it can be valuable to get feedback.

Focus groups

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In a focus group, you’ll gather together a small group of people to discuss a design or idea. The fact that focus groups involve a group of people is a double-edged sword.

On one hand, you can get people to tease out of their colleagues’ things that they might not have thought to say on their own.

On the other hand, for a variety of psychological reasons, people may be inclined to say polite things or generate answers completely on the spot that is totally uncorrelated with what they actually believe or what they would actually do.

Focus groups can be a particularly problematic method when you’re looking at trying to gather data about taboo topics or about cultural biases.

Feedback from experts

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In addition to having users try your interface, it can be important to eat your own dog food and use the tools that you build yourself. When you’re getting feedback from experts it can often be helpful to have some kind of structured format.

Much like the rubrics that you’ll see in your project assignments, and for getting feedback on user interfaces one common approach to this structured feedback is called Heuristic Evaluation. It was pioneered by Jacob Neilson.

Comparative Experiments

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This means taking two or more distinct options and comparing their performance to each other.

These comparisons can take place in lots of different ways. They can be in the lab, they can be in the field, they can be online. These experiments can be, more or less, controlled, and they can place over shorter or
longer durations.

What you’re trying to learn here is which option is the more effective. And more often, what are the active ingredients, what is the variable that matter in creating the user experience that you seek.

Comparative experiments have an advantage over surveys in that you get to see the actual behavior as opposed to self-report. And they can be better than usability studies because you’re comparing multiple alternatives.

This enables you to see what works better or worse, or at least what works differently. Comparative feedback is also often much more actionable. However, if you’re running controlled experiments online, you don’t get to see much about the person that’s on the other side of the screen. And if you’re inviting people into your office or lab, the behavior you’re measuring
might not be very realistic.

If realistic longitude in behavior is what you’re after, participant observation may be the approach for you.

This approach is just what it sounds like, observing what people will actually do in their actual work environment. And it’s more long-term
evaluation can be important for uncovering things that you might not see
shorter term more controlled scenarios.

Nearly all experiments seek to build a theory on some level. We can take some things to be more irrelevant and other things to be less relevant.

If you have a theory that’s sufficiently formal mathematically that you can make predictions, then you can compare alternative interfaces using that model without having to bring people in. This makes it possible to try out
a number of alternatives really fast.

You’ll probably want to pick the right method for the right task, and here are some issues to consider. If you did it again, would you get the same thing? Another is generalizability and realism. Does this hold for people other than 18-year-old upper-middle-class students, who are doing this for
course credit or a gift certificate? Is this behavior also you’d see in the real world or only in a more stilted lab environment?

Comparisons are important because they can tell you how the user experience would change with different interface choices, as opposed to just a people liked its study.

It’s also important to think about how to achieve these insights efficiently and not chew up a lot of resources especially when your goal is practical.

So, evaluating designs with people is both easier and more valuable than many people expect. And there’s an incredible light bulb moment that happens when you actually get designs in front of people and see how they use them.

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Inspired by Scott Klemmer

Written by

Senior Experience Designer in Google.

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