Should You Use Nonparametric Methods to Analyze UX Data?

Near the top of the list of concerns people have when using statistics with UX data is what to do with non-normal data. If you remember only a few things from statistics class, you might recall something about data needing to look like the infamous bell curve; more specifically, it needs to be normally distributed.

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Is UX Data Normally Distributed?

If you took an intro to stats class (or if you know just enough to be dangerous), you probably recall two things: something about Mark Twain’s “lies, damned lies …,” and that your data needs to be normally distributed. Turns out both are only partly true. Mark Twain did write the famous quote, but he

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Eight Laws of Statistics

Statistics doesn’t have a Magna Carta, constitution, or bill of rights to enumerate laws, guiding principles, or limits of power. There have been attempts to articulate credos for statistical practice. Two of the most enduring ones are based on the work by Robert P. Abelson, a former statistical professor at Yale. If Abelson wasn’t the

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Sample Sizes for Comparing SUS to a Benchmark

The System Usability Scale (SUS) has been used in industrial user experience research since the mid-1980s. Despite its age, the SUS is still a popular measure, widely used in benchmark tests of software products to measure perceived usability. One reason for its popularity is the extent to which its measurement properties have been comprehensively studied

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Five Styles of Statistical Rhetoric

When learning statistics, you’ll encounter many formulas based on principles of probability and mathematics. But statistics isn’t just a formulaic process where you enter data and are told what to do. Statistics should guide, not dictate, decisions. In making decisions, though, there are different styles of interpreting data. Although a lot of people think statistics

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Censuses, Polls, Surveys, and Questionnaires:
How Are They Different?

Surveys are one of the most popular methods in applied research. While many have argued that surveys are overused, it’s hard to believe that surveys have no place in multi-method UX research. When conducting survey-based research, you’ll often encounter the terms census, poll, and questionnaire used in conjunction with—and often interchangeably with—the term survey. But

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Accuracy of Three Ways to Estimate SUS with the UX-Lite

In a previous article, we described three ways to estimate SUS scores from UX-Lite™ (and UMUX-Lite) scores, using either both items (perceived measures of Ease and Usefulness) or the Ease item only: Two-item interpolation: Scaling the mean of both items to a 100-point scale (Lite). One-item interpolation: Scaling just the Ease item to a 100-point

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For Statistical Significance, Must p Be < .05?

If you know even just a little about statistics, you know that the value .05 is special. When the p-value obtained from conducting a statistical test falls below .05, it typically gets a special designation we call statistically significant. This is the conventional threshold for publishing findings in academic journals, and consequently, it is ascribed

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Measuring UX: From the UMUX-Lite to the UX-Lite

For the past few years, we’ve written extensively about our research and usage of the UMUX-Lite. That research has followed the increase in popularity of this compact questionnaire. From its initial publication in 2013, the UMUX-Lite (Usability Metric for User Experience—Lite Version) has become an increasingly popular measure of perceived usability. Figure 1 shows the

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A Review of Alternates for the UMUX-Lite Usefulness Item

The UMUX-Lite is a popular two-item measure of perceived usability that combines perceived ratings of Ease and Usefulness, as shown in Figure 1.     Figure 1: Standard version of the UMUX-Lite (standard item wording with five-point scales). Since we began regularly using the UMUX-Lite in our practice, we’ve had numerous clients ask whether it

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