Which of the following is NOT a method to test the usability of technical documents?

Choosing "historical analysis" as the method that is not used to test the usability of technical documents is accurate because historical analysis focuses on examining previous documents, practices, or outcomes rather than actively assessing the current usability of a document. Usability testing methods, on the other hand, are direct approaches used to evaluate how effectively users can interact with a document.

User testing involves having real users perform tasks with the document to evaluate their experience and identify issues. Observation of user interactions allows researchers to see firsthand how users engage with the document, providing insights into usability challenges. Surveys solicit feedback directly from users about their experiences and perceptions of the document's usability.

In contrast, historical analysis does not provide current, actionable insights regarding the usability of a document; instead, it looks backwards, making it less relevant for testing current usability levels.