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  • anna williams thinks this is interesting:

some evidence that the additional cognitive load of concurrent think aloud causes participants to be less successful with their tasks. For example, van den Haak, de Jong, and Schellens (2004) found that participants in a usability study of a library website were successful with only 37% of their tasks when using concurrent think aloud, but they were successful with 47% when using RTA. But keep in mind that it will take almost twice as long to run sessions using RTA.

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Cover of Measuring the User Experience, 2nd Edition

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DAWSON REPORT - didnt want to use this, as time on task wasn't the best meaure. plus particioant would be more aware that being filmed and more conscious about what doing. Finally tine on task wasn't the most important measure