Key points
• Sample size estimation is an important part of planning a user study, especially when the cost of a sample is high.
• Different types of studies require different methods for sample size estimation. This chapter covers methods for user studies (such as summative usability studies) that use measurements that are continuous (such as time on task), multipoint scale (such as usability questionnaires), or discrete (such as successful task completions).
• Different research goals (such as estimation of a value, comparison with a benchmark, or comparison among alternatives) require different methods for sample size estimation.
• To obtain a sample size estimation formula, take the formula for the appropriate test and solve for n.
• Sample ...
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