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I am performing a heuristic evaluation of mobile apps. My worry is, as a single reviewer I am not able to find more than ~35% of the problems - as Nielsen suggests.

I am reviewing mobile apps.

Does the case of simple interface mean I can find more than 35% of the problems? i.e. does system complexity mean it's harder to find usability problems?

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I assume you are referring to this – Roger Attrill Feb 21 '13 at 11:09
Yes, among others – thevangelist Feb 21 '13 at 11:21

System complexity in UX is analogous to code complexity. Think of each option or interaction as another conditional or fork where a user may chose one of several actions.

If that principle holds (which I would suggest it does), you can consider much of the research on code complexity and code reviews as being relevant. All of those studies that I am aware of show that as the complexity of a system increases, so does the difficulty in getting full test coverage, and consequently the number of errors tends to increase.

This is one of the main reasons behind the drive for small modular libraries that are simpler and easier to test.

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System complexity affects fixed and variable costs of evaluation, not a single individual's ability to find all usability problems.

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Any references to studies about my question? – thevangelist Feb 21 '13 at 11:21
Well there is NNG's own analysis of 83 case studies although that doesn't specifically allow you to extract information about single user reviews, but does indicate that for a range of different projects (we presume of varying size) then the ROI is statistically best at around 5 testers. – Roger Attrill Feb 21 '13 at 12:25

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