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## Chapter Review Questions

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1. Assume you need to conduct a single-shot (not iterative) formative usability study that can detect about 85% of the problems that have a probability of occurrence of 0.25 for the specific participants and tasks used in the study (in other words, not 85% of *all* possible usability problems, but 85% of the problems discoverable with your specific method). How many participants should you plan to run?

2. Suppose you decide that you will maintain your goal of 85% discovery, but need to set the target value of *p* to 0.2. Now how many participants do you need?

3. You just ran a formative usability study with four participants. What percentage of the problems of *p* = 0.5 are you likely to have discovered? What about *p* = 0.01, *p* = 0.9, or *p* = 0.25?