Usability Engineering: Focus on the users
The usability of interactive products has become an important feature of quality and is a major competitive factor. But what does usability mean and which impact does it have on software development?
Who has not found himself in a situation where one was unable to do even simple tasks with the new cell phone? Or webpages where you can‘t find the information you are looking for, no matter how long you click around? Computer programs that waste your precious time, because they are not working the way they are supposed to. If we find ourselves in this situation we are often frustrated and want to abandon this software immediately.
Interactive products can be technically sophisticated and offer a lot of great features, but still the users are not satisfied. Why is that?
Three important factors determine the success of a product: the helpfulness, the usability and the acceptance of the users. The better the user-centered research in advance and during the product design phase, the more successful the product will be.
What is usability?
Since 1997, the sense of usability is normed. In DIN EN ISO 9241 you can find the requirements on the ergonomics between man-machine interactions. Sections of the norm deal with the requirements on usability. According to DIN EN ISO 9241-11, Usability is “the degree, in which a product can be used by specific users to achieve specific goals efficiently, effective and satisfactorily”.
This definition shows that usability cannot be rated good or bad if separated from the software. It always depends on the kind of user, the tasks, his tools and his environment. This context must be known exactly to create usable products and to rate them. (see figure 1) Therefore it is not sufficient to put in the usability aspect of user interfaces at the end of the development process. Usability Engineering provides the tools to integrate User-centered Design from the beginning into your development process.
User-centered from the beginnin
At the start of a project the different user groups are identified and analyzed. Users are observed in their real work environment to learn and understand the actual work flow and their needs (Contextual Inquiry). The goal is to narrow down the suitable requirements to the product. This ensures early in the project that the application not only works good but also meets all three usability-criteria (see figure 2).
With the help of personas and scenarios, the results of the analysis are being transferred into the models and are the basis for user interfaces that will fit the need. These drafts will be validated by user tests during the iterative prototyping. Errors can be found very early and this will save high post-production costs.
Example: Ticket machine
Ticket machines are often used as an example for bad usability, though they offer a high degree of effectivity and effiency. But only if you know how to use them.
However, inexperienced users – tourists or occasional passengers - who are not familiar with the specific fee system and their booking conditions, or are not familiar with the actual usage of a ticket machine need far more time to get themselves a ticket. Some do not even manage to get a ticket at all.
But what helps? The developers of the machine should not assume that customers have the same knowledge about the fee system, fare zones and product names like the service employees. Rather they should start asking: What are the goals of the people that buy a ticket? What is their approach to this? Which mental models do they carry to perform this act? And this can be observed the best at the ticket counter.
Usability starts with looking over the shoulder so the users. Only if you understand the user, you are able to produce better systems that do justice to the human thinking and acting.
Contact person: Andrea Rösch; firstname.lastname@example.org