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Sample Sizes for Comparing Net Promoter Scores
Sample size estimation is a critical step in research planning, including when you’re trying to detect differences in measures like Net Promoter Scores. Too small of a sample and you risk not being...
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Sample Sizes for Comparing Dependent Proportions
Sample size estimation is an important part of study planning. If the sample size is too small, the study will be underpowered, meaning it will be incapable of detecting sufficiently small differences...
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Should You Report Numbers or Percentages in Small-Sample Studies?
“Don’t include numbers when reporting the results of small-sample research studies!” “If you must, definitely don’t use percentages!” “And of course, don’t even think about using statistics!” We...
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Sample Sizes for Comparing Rating Scale Means
Are customers more satisfied this quarter than last quarter? Do users trust the brand less this year than last year? Did the product changes result in more customers renewing their subscriptions? When...
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How Do Changes in Standard Deviation Affect Sample Size Estimation?
The standard deviation is the most common way of measuring variability or “dispersion” in data. The more the data is dispersed, the more measures such as the mean will fluctuate from sample to sample....
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Changes to Rating Scale Formats Can Matter, But Usually Not That Much
Few things seem to elicit more opinions, exaggerations, and accusations than rating scale response options. From the “right” number of points, the use (or not) of labels, and the presentation order (to...
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Top Box, Top-Two Box, Bottom Box, or Net Box?
One box, two box, red box, blue box … Box scoring isn’t just something they do in baseball. Response options for rating scale data are often referred to as boxes because, historically,...
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Sample Sizes for Usability Studies: One Size Does Not Fit All
“How many participants should you run in a usability study?” How many times have you heard that question? How many different answers have you heard? After you sift through the non-helpful ones,...
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What You Get with Specific Sample Sizes in UX Problem Discovery Studies
What sample size should you use for a problem discovery (formative) usability study? In practice, the answer is based on both statistics AND logistics. A statistical formula will tell you an optimal...
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How Many People Do You Need to See Trip on Your Carpet Before Fixing It?
You invite your friends over for a gathering at your house. As the party gets started, you watch in horror as a friend trips on the edge of your carpet before she even takes the first sip of her...
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