To incorporate users' opinions into the evaluation phase early in the software
documentation development stage, the critical incident technique was used to identify
usability problems in a fault free software user document. The critical incidents were used
to modify the original document to improve its usability. To test whether the modified
document was better in usability than the original document, an experiment was conducted
to compare objective measures and subjective ratings.
Four objective measures included nutnber of errors, task completion time,
document reading time, and number of personal helps requested. In addition, subjective
ratings on ease of use, accuracy of information, inconsistencies, ease of learning,
completeness, helpfulness of figures, and ease of understanding were compared between
the two documents.
The analyses showed that for 3 of 4 objective measures and 7 out of 9 subjective
ratings, the new document was better and easier to use. In sonle cases, this difference was
task specific. Generally, easier tasks accounted for better objective measures and more
favorahle subjective ratings.
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