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In a usability test you typically collect some type of performance data: task times, completion rates and perhaps errors or conversion rates. It is also a good idea to use some type of questionnaire which measures the perceived ease-of-use of an interface. This can be done immediately after a task using a few questions (post-task questionnaires). It can also be done after the usability testing

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The System Usability Scale (SUS) is the most popular standardized usability questionnaire. SUS was developed about 20 years ago at Digital Equipment Corporation by John Brooke. It's popular for two reasons: it's free and short (at only 10 questions). The process of taking a set of ordinary questions and making it into a psychometrically valid and reliable "standardized" questionnaire essentially involves having many users answer

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Would you recommend your cell-phone to a friend?  How about the rental car company you just used?  Customer loyalty is an important attribute of a product or service's long-term viability.  There are many ways to measure the construct of customer satisfaction and loyalty and they usually involve questionnaires, such as the American Customer Satisfaction Index .  One of the more popular methods is something called

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Is there such thing as usability? This might sound like a silly question considering the industry around usability testing and user experience consulting (not to mention this website). But you can't touch usability and there is no usability thermometer to measure its presence or absence.  While we can talk about usability and know it when we see it (or really, know it when we don't

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Imagine a marketing department asking for more money to conduct a direct-mail campaign and their only justification was that marketing is a critical business advantage. Now contrast that with an argument that showed that in a previous direct-mail campaign the response rate of 3% was more than twice the industry average and was achieved from testing a sample of the campaign on customers. The test

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Why isn't usability testing done more?  And when it is done why is the sample size small? One major reason is the cost. It takes a lot of money and time to bring users into a lab and conduct a usability test. Even if users don't get compensated for their time, it still takes a lot of time for a test facilitator to prepare for

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Does a PhD pay off financially? I recently helped conduct the statistical analysis of the UPA 2009 salary survey[pdf], and used this opportunity to look into the data to see if I could calculate how much a PhD affects salaries in this profession.  The dataset contains salary information for a wide range of jobs in the profession—usability engineers, designers, managers and information architects. The vast

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Have you ever watched a user perform horribly during a usability test only to watch in amazement as they rate a task as very easy to use? I have, and as long as I've been conducting usability tests, I've heard of this contradictory behavior from other researchers. Such occurrences have led many to discount the collection of satisfaction data altogether. In fact I've often heard

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How many users will complete the task and how long will it take them? If you need to benchmark an interface, then a summative usability test is one way to answer these questions. Summative tests are the gold-standard for usability measurement. But just how precise are the metrics? Just as a presidential poll uses a sample to estimate outcomes for the entire population, usability tests

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Neilsen derives his "five users is enough" formula from a paper he and Tom Landauer published in 1993. Before Nielsen and Landauer James Lewis of IBM proposed a very similar problem detection formula in 1982 based on the binomial probability formula.[4] Lewis stated that: The binomial probability theorem can be used to determine the probability that a problem of probability p will occur r times

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