Accompanying the reduction in programming errors with the redesigned interface was a statistically significant improvement in task completion time. Nurses were able to complete programming tasks with the redesigned interface 18% faster than with the existing interface, despite having no prior experience with the former and several years of experience with the latter. This improvement can be attributed to not only the increased clarity of messages and functional organization of the control panel, but also to the fact that there are fewer steps in the new dialogue structures for the redesigned interface. Furthermore, with significantly fewer programming errors being made, less time was wasted recovering from errors.
The workload associated with the redesigned interface was found to be 14% lower than that associated with the current interface. Although subjective mental workload was the only measure that did not yield statistical significance, this result should be interpreted within the context of experience. Despite having less familiarity and experience with the new interface, nurses reported workload levels similar to that associated with the existing interface.
In addition to the fact that a low level of mental workload was achieved with minimal training on the new interface, workload for unfamiliar tasks decreased significantly with practice on the new interface. An interaction between interface, task, and repetition led to a more substantial reduction in workload over two repetitions for the new interface with the Continuous and PCA+ Continuous tasks compared to that for the old interface. This suggests that with the redesigned interface, nurses found it progressively easier to program these unfamiliar modes. Meanwhile, the workload reduction was less pronounced with the old interface, and even increased for the Continuous mode, despite the advantage of familiarity and experience with the old interface.