Usability 101: Introduction to Usability

Summary:
How to define usability? How, when, and where can you improve it? Why should you care? This overview answers these basic questions.

This is the article to give to your boss or anyone else who doesn't have much time, but needs to know the basic usability facts.

What (Definition of Usability)

Usability is a quality attribute that assesses how easy user interfaces are to use. The word "usability" also refers to methods for improving ease-of-use during the design process.

Usability is defined by five quality components:

• Learnability: How easy is it for users to accomplish basic tasks the first time they encounter the design?
• Efficiency: Once users have learned the design, how quickly can they perform tasks?
• Memorability: When users return to the design after a period of not using it, how easily can they reestablish proficiency?
• Errors: How many errors do users make, how severe are these errors, and how easily can they recover from the errors?
• Satisfaction: How pleasant is it to use the design?

There are many other important quality attributes. A key one is utility, which refers to the design's functionality: Does it do what users need? Usability and utility are equally important: It matters little that something is easy if it's not what you want. It's also no good if the system can hypothetically do what you want, but you can't make it happen because the user interface is too difficult. To study a design's utility, you can use the same user research methods that improve usability.

Why Usability is Important

On the Web, usability is a necessary condition for survival. If a website is difficult to use, people leave. If the homepage fails to clearly state what a company offers and what users can do on the site, people leave. If users get lost on a website, they leave. If a website's information is hard to read or doesn't answer users' key questions, they leave. Note a pattern here? There's no such thing as a user reading a website manual or otherwise spending much time trying to figure out an interface. There are plenty of other websites available; leaving is the first line of defense when users encounter a difficulty.

The first law of e-commerce is that if users cannot find the product, they cannot buy it either.

For intranets, usability is a matter of employee productivity. Time users waste being lost on your intranet or pondering difficult instructions is money you waste by paying them to be at work without getting work done.

Current best practices call for spending about 10% of a design project's budget on usability. On average, this will more than double a website's desired quality metrics and slightly less than double an intranet's quality metrics. For software and physical products, the improvements are typically smaller — but still substantial — when you emphasize usability in the design process.

For internal design projects, think of doubling usability as cutting training budgets in half and doubling the number of transactions employees perform per hour. For external designs, think of doubling sales, doubling the number of registered users or customer leads, or doubling whatever other desired goal motivated your design project.

How to Improve Usability

There are many methods for studying usability, but the most basic and useful is user testing, which has three components:

• Get hold of some representative users, such as customers for an e-commerce site or employees for an intranet (in the latter case, they should work outside your department).
• Ask the users to perform representative tasks with the design.
• Observe what the users do, where they succeed, and where they have difficulties with the user interface. Shut up and let the users do the talking.

It's important to test users individually and let them solve any problems on their own. If you help them or direct their attention to any particular part of the screen, you have contaminated the test results.

To identify a design's most important usability problems, testing five users is typically enough. Rather than run a big, expensive study, it's a better use of resources to run many small tests and revise the design between each one so you can fix the usability flaws as you identify them. Iterative design is the best way to increase the quality of user experience. The more versions and interface ideas you test with users, the better.

User testing is different from focus groups, which are a poor way of evaluating design usability. Focus groups have a place in market research, but to evaluate interaction designs you must closely observe individual users as they perform tasks with the user interface. Listening to what people say is misleading: you have to watch what they actually do.

When to Work on Usability

Usability plays a role in each stage of the design process. The resulting need for multiple studies is one reason I recommend making individual studies fast and cheap. Here are the main steps:

1. Before starting the new design, test the old design to identify the good parts that you should keep or emphasize, and the bad parts that give users trouble.
2. Unless you're working on an intranet, test your competitors' designs to get cheap data on a range of alternative interfaces that have similar features to your own. (If you work on an intranet, read the intranet design annuals to learn from other designs.)
3. Conduct a field study to see how users behave in their natural habitat.
4. Make paper prototypes of one or more new design ideas and test them. The less time you invest in these design ideas the better, because you'll need to change them all based on the test results.
5. Refine the design ideas that test best through multiple iterations, gradually moving from low-fidelity prototyping to high-fidelity representations that run on the computer. Test each iteration.
6. Inspect the design relative to established usability guidelines, whether from your own earlier studies or published research.
7. Once you decide on and implement the final design, test it again. Subtle usability problems always creep in during implementation.

Don't defer user testing until you have a fully implemented design. If you do, it will be impossible to fix the vast majority of the critical usability problems that the test uncovers. Many of these problems are likely to be structural, and fixing them would require major rearchitecting.

The only way to a high-quality user experience is to start user testing early in the design process and to keep testing every step of the way.

Where to Test

If you run at least one user study per week, it's worth building a dedicated usability laboratory. For most companies, however, it's fine to conduct tests in a conference room or an office — as long as you can close the door to keep out distractions. What matters is that you get hold of real users and sit with them while they use the design. A notepad is the only equipment you need.

可用性101：可用性的介绍

摘要：
        可用性该如何定义？你可以如何、在什么时候、在哪里提高可用性？为什么应该重视它？这篇概述可以回答这些基本问题。

        这篇文章是给你的老板、或者其他没有很多时间但又需要了解基本可用性常识的人看的。

可用性的定义

        可用性是评估用户界面容易使用的程度的一种属性。“可用性”这个词语也指在设计过程中提高易用性的方法。

可用性由五个属性组成定义：
·可学习性：初次接触这个设计时，用户完成基本任务的难易程度。
·效率：用户熟悉这个设计后，完成任务的速度。
·可记忆性：在一段时间没有使用之后再次使用该设计，用户重新熟练操作的难易程度
·出错：用户出了多少错误，这些错误有多严重，从错误中恢复容易吗？
·满意度：使用这个设计的用户满意度。

        还有很多其他重要的属性。一个重要的就是实用性，即是设计的功能性：它所做的迎合用户需要吗？可用性和实用性是同样重要的：如果不是你想要的那无关紧要。假设系统可以做到你想要的，但却因为用户界面难用导致你无法使用，那么则是糟糕的。你同样可以运用提高可用性的用户研究方法去研究实用性。

为什么可用性这么重要？

        在网络上，可用性是生存的必备条件。如果一个站点难易使用，人们会离开它。如果主页不能清晰地说明这间公司可以提供什么和用户可以在这网页上做什么，人们会离开它。如果用户在站点上迷失，他们会离开。如果一个站点的信息难以阅读或者没有回答用户的关键问题，他们会离开。注意到一种模式了吗？用户不会自动去阅读网页，又或者是花费大量时间去弄懂一个界面。还有很多其它可用的网站；当用户遇到困难时，离开是第一抉择。

        电子商务的第一法则是，如果用户不能找到商品，他们就不会购买它。

        在互联网上，可用性事关雇员生产力。你支付了雇员的工资，但他们没有把工作完成，那么你浪费的钱相当于用户在你网站上迷失和费力解读憋足的说明所浪费的时间。

        现在，实践证明最好在设计项目预算里花费10%在可用性上。总体来说，这样是两倍大于网页的期望绩效，稍微少于互联网绩效。对于软件和物理产品来说，这样提高的效果比较小，但仍然有价值——当你强调在设计过程中融入可用性。

        对内部设计项目，可以通过对培训预算减半，增加每小时交易雇员的数量去加大可用性的投入。而对于外部设计项目，则增加销量，增加注册用户或者顾客数量，或者增加其它可以推进你设计项目的想法。

怎样提高可用性

        有很多研究可用性的方法，但是最基本和最有用的是用户测试，包括三个部分：

·选取一些有代表性的用户，例如电子商务站点的顾客或者互联网的雇员（在之后的流程里，他们会在你部门以外工作）。
·让用户在系统里完成一些有代表性的任务。
·观察用户做了些什么，他们在哪里操作成功了，在用户界面上哪里遇到困难。让用户说话但你应该保持沉默。

        独立地测试用户和让他们自己去解决问题，这是很重要的。如果你帮助他们或者引导他们在屏幕上任何特殊部分上的注意力，那么你已经影响了测试结果。

        要找出设计中最重要的可用性问题，测试五个用户就已经足够了。比起大型昂贵的研究，善用好资源去进行许多小的测试和在每个测试之后迭代设计，你可以根据发现的可用性问题去改善它。交互设计是提高用户体验的最好方法。你跟用户测试越多的版本和界面想法，效果越好。

        用户测试跟焦点小组不同，焦点小组是评估设计中可用性比较憋足的方法。虽然焦点小组在市场研究中起到一定的作用，但对于评估交互设计，你必须仔细观察每个用户如何操作用户界面的任务。不要听用户说的，应该观察他们所做的。

什么时候开展可用性工作

        可用性在设计的每个阶段都有其作用。根据大量研究得出的结果，我建议多快好省地进行个体学习。以下是主要步骤：

1. 在进行新设计之前测试旧版本，以发现应该保留或者强调的好的部分，以及给用户添麻烦的差的部分。
2. 除非你正在互联网公司工作，否则通过应该测试竞争对手相似特征的设计来获得便宜的数据（如果你在互联网公司工作，请阅读互联网设计年度报告以从其它设计中学习）。
3. 对用户在自然居住环境下的行为进行广泛研究。
4. 为一个甚至更多的新设计意念制作纸面模型，然后去测试它们。因为需要基于测试结果去修改，所以你投资在这些设计意念的时间越少越好。
5. 经过大量的迭代完善经过测试的设计计划，从低保真模型逐渐过渡到可以在电脑运行的高保真原型。测试每个迭代版本。
6. 将设计对照已有的可用性指南，看是否源于你自己早期的研究或者已经公开的研究结果。
7. 一旦你决定实现最终设计，请再次测试它。细致的可用性问题经常在实现期间出现。

        不要等到已经有了一个完整的设计才进行用户测试。由于测试没有覆盖到，这样的话就不可能修复大多数严重的可用性问题。许多这样的问题都是结构性的，修复他们的话就要进行主要的重构。

        提高用户体验唯一的方法就是在设计过程中尽早地开始用户测试，以及每一步都坚持做测试。

在哪里测试

        如果你每周至少研究一个用户，那么建立一个可用性实验室是值得的。对绝大多数公司来说，无论如何，可以在会议室或者办公室进行测试——只要你关上门隔绝外来干扰。重要的是你找到真正的用户，当他们使用这个设计时坐在他们旁边。而你需要的唯一设备是一本笔记本。