The Importance of Lower Common Denominator UX Research Testing

Executive Summary

  • Lower common denominator UX testing looks for bottlenecks in the UX with lower than average skilled computer users.
  • We cover why LCD UX testing is part of our approach.


Applications are developed with high-functioning computer users. For this reason, much of the application will have already been tested and be function for higher functioning computer users without much additional UX testing. For this reason, middle and lower-functioning computer users are the most valuable user subjects for most UX testing endeavors. We cover how we employ lower standard denominator UX testing in our approach.

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Profiling Lower Common Denominator Test Subjects

Some people make a part-time side income by being “professional testers.”

There are several companies/websites out there that recruit UX testers. However, they are generally high-functioning computer users.

But there is little point in testing this group. Usually, one already has input from this type of test subject as the developer and designer are also high functioning computer users. And only in unusual circumstances will this be a representative sample of the population of users. This is the essential topic of statistical research — representativeness. It is a tricky topic because the lower functioning users are not going to tend to want to sign up to be a tester.

The problem, of course, is that high-functioning computer users are the easiest to find. Therefore, many UX testing goes forward by counting high-functioning computer users. The result is that the application or website ends up developed at too high of complexity for the target user. This is, of course, the topic of sampling — and sampling issues are rampant throughout research, particularly in commercial research. 

Lower Common Denominator Versus Domain Expertise

When we say LCD, we are only referring to computer usage skills. In terms of interpreting the content of the tested item (app, website etc..), there is no point in having lower domain expertise test subjects than the target group.


Lower common denominator testing is necessary to balance against the bias of high functioning computer users that are already part of the design and build process.

NNg has a good video on finding representative users.