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The Importance of Task Order Randomizing during a Usability Test

Minimize Lurking Variables Getting Warmed Up Without task randomization, so-called lurking variables can taint your data–usually not enough that it’s devastating but often it’s noticeable. One lurking variable when analyzing task times is the user’s tendency to perform better on the later tasks and worse on the earlier tasks. It’s human nature: someone hands you

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What’s the 1.5σ Shift and Does it Apply to Software Usability?

If you compare the sigma value on this site with other values published in most six sigma literature, it’s important to know that a 1.5 σ “shift” is usually added. For example, if you see a sigma value of 1.08σ on measuringusability.com and want to compare it to other sources then add 1.5. The resulting

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Why 6σ is Not Limited to Manufacturing Processes

Six Sigma History and Overview Six Sigma was started in manufacturing for processes that are duplicated thousands and millions of times in something like the placement of a spot weld on sheet metal on a power turbine and being able to predict the failure rate of that part’s weld. If you can measure and control

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How Do You Calculate a Z-Score/ Sigma Level?

The benefit of using a z-score in usability metrics was explained in “What’s a Z-Score and why use it in Usability Testing?” this article discusses different ways of calculating a z-score. The short answer is: It depends on your data and what you’re looking for. If you’ve encountered the z-score in a statistics book you

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The Risks of Discounted Qualitative Studies:

The discerning usability analyst should employ a mix of both qualitative and quantitative methods when discovering usability problems. The risks of relying heavily on a qualitative approach can lead to a severe misdiagnosis especially when usability problems are difficult to detect. This article is a response to Nielsen’s “The Risk of Quantitative Studies” and shows

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