有些人认为可用性是非常昂贵的,复杂的是,并且用户测试应该为罕见的网络设计项目保留,具有巨大的预算和豪华的时间表。不对。精心制作的可用性测试是浪费资源。最好的结果来自于测试不超过5个用户,并在您提供的作用时运行尽可能多的小测试。

在早期的研究中,tomlandauer和我展示了在可用性测试中发现的可用性问题的数量N.users is:

N(1-(1-L.N.

在哪里Nis the total number of usability problems in the design andL.is the proportion of usability problems discovered while testing a single user. The typical value ofL.是31%,平均我们研究过大量项目。绘制曲线L.=31% gives the following result:

Increase in proportion of usability problems found by number of test users

这most striking truth of the curve is thatzero users give zero insights

一旦收集来自a的数据单个测试用户, your insights shoot up and you have already learned almost a third of all there is to know about the usability of the design. The difference between zero and even a little bit of data is astounding.

当你测试second user, you will discover that this person does some of the same things as the first user, so there is some overlap in what you learn. People are definitely different, so there will also be something new that the second user does that you did not observe with the first user. So the second user adds some amount of new insight, but not nearly as much as the first user did.

third user将使用第一个用户或与第二个用户一起观察到的很多事情,甚至是您已经看过两次的东西。此外,当然,第三个用户将生成少量的新数据,即使不像第一用户和第二个用户一样多。

像你一样add more and more users, you learn less and less因为你会再次又一次地看到同​​样的事情。没有真正需要多次观察同样的事情,并且您将非常有动力返回绘图板并重新设计网站以消除可用性问题。

在第五个用户之后,你重复观察同样的发现却没有学到很多新的东西,这是在浪费时间。

Iterative Design

这curve clearly shows that you need to对至少15个用户进行测试,以发现所有可用性问题in the design. So why do I recommend testing with a much smaller number of users?

最主要的原因是你最好把你的预算分配给用户在许多小测试中测试而不是在一个精心设计的研究中吹掉一切。让我们说你有资金招募15名代表客户,并让他们测试你的设计。伟大的。将此预算用于3项研究,每个研究有5个用户!

You want to run multiple tests because the real goal of usability engineering is to improve the design and not just to document its weaknesses. After the first study with five participants has found 85% of the usability problems, you will want to fix these problems in a redesign.

创建新设计后,您需要再次测试。即使我说重新设计应该“修复”在第一项研究中发现的问题,但事实是你思考新设计克服了问题。但由于没有人可以设计完美的用户界面,因此无法保证新的设计实际上解决了问题。第二次测试将发现修复是否有效或无论是没有。此外,在引入新设计时,即使旧的设计已修复,始终存在引入新的可用性问题的风险。

此外,有5个用户的第二次研究将发现在第一轮测试中未发现的大部分剩余剩余的15%的原始可用性问题。(仍有2%的原始问题剩下 - 它们将不得不等到第三项研究才能确定。)

最后,第二项研究将能够探测到基本结构的可用性深入of the site, assessing issues like information architecture, task flow, and match with user needs. These important issues are often obscured in initial studies where the users are stumped by stupid surface-level usability problems that prevent them from really digging into the site.

因此,第二项研究既可以作为第一项研究结果的质量保证,也有助于提供更深入的见解。第二项研究总是会产生一个新的(但更小的)可用性问题清单,以便在重新设计时加以解决。同样的观点也适用于这个重新设计:并不是所有的修复都能工作;在清理接口之后,一些更深层次的问题将会被发现。因此,还需要进行第三次研究。

这ultimate user experience is improved much more by 3 studies with 5 users each than by a single monster study with 15 users.

为什么不使用单个用户测试?

You might think that 15 studies with a single user would be even better than 3 studies with 5 users. The curve does show that we learn much more from the first user than from any subsequent users, so why keep going? Two reasons:

  • 总有一个被误导的刺激的风险ious behavior of a single person who may perform certain actions by accident or in an unrepresentative manner. Even 3 users are enough to get an idea of the diversity in user behavior and insight into what's unique and what can be generalized.
  • 用户测试的成本效益分析根据测试风格,提供大约3或5个用户的最佳比率。规划和运行一项研究总是有一个固定的初始成本:最好在多个用户的研究结果中降低这个启动成本。

何时测试更多用户

You need to test additional users when a website has几个高度不同的用户组. 这个公式只适用于那些将以相当相似的方式使用该网站的可比用户。

If, for example, you have a site that will be used by both children and parents, then the two groups of users will have sufficiently different behavior that it becomes necessary to test with people from both groups. The same would be true for a system aimed at connecting purchasing agents with sales staff.

即使用户群体差异很大,两个群体的观察结果仍会有很大的相似性。毕竟,所有的用户都是人。此外,许多可用性问题都与人们与Web交互的基本方式以及其他网站对用户行为的影响有关。

在测试多个完全不同的用户组时,不需要像在单个用户组的单个测试中那样包含每个组的成员。观察结果之间的重叠将确保对每组人数较少的人进行测试,从而获得更好的结果。我建议:

  • 每类别中的3-4个用户,如果测试两组用户
  • 如果测试三个或更多用户组,则每个类别中有3个用户(您总是希望至少有3个用户,以确保您涵盖了组内行为的多样性)

Reference

Nielsen,Jakob和Landauer,Thomas K.:“找到可用性问题的数学模型”1993年ACM国际会议记录(Amsterdam, The Netherlands, 24-29 April 1993), pp. 206-213.

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