Identifying Potential Use Errors

When working with usability engineering and interface design, a very effective and systematic way to help you identify potential use errors is to use the ‘PCA analysis’. The PCA analysis breaks down each use step into three components: Perception, Cognition, and Action, hence the name PCA.

Breaking each step of the users interaction with the device down to these three components, will help you understand what each task requires from the user.

A use error or difficulty is likely to occur if the user is unable to meet one of these task requirements related to perception, cognition and action. In this way, the PCA analysis, can be a very usefull tool to help you identify use errors related to hazardous situations.

User-Device Interaction Model

We have now looked at how steps in user tasks can be broken down into Perception, Cognition and Action. The PCA analysis is derived from this model of user-device interaction. The model illustrates a user interacting with a device through a user interface. The user provides input to the device (e.g., pressing a button), which the device processes to provide an output back through its interface.

The user must be able to perceive this output, understand what to do with it, and act accordingly. This model helps identify sources of potential use errors or hazardous situations caused by device output. We differentiate between:

1. Hazardous situations caused by a response of the medical device
2. Hazardous situations caused by a user action or lack of action based on information from the medical device

PCA Analysis Provides Valuable Input to the User Interface Design

We have introduced the PCA analysis and the user-device interaction model. Let’s consider a simple example of how to apply PCA analysis to (1) identify potential use errors and (2) define design input requirements: