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5.2

Theory of usability
ISO-9241 International standard defines Usability as:

«The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use».

Usability: extent of Effectiveness, Efficiency and Stisfaction

Consequently each product offer subjective usability, which can be measures through special methods:

Expert evaluation

Enables to measure the product’s usability through qualitative methods.
This means, that experts can evaluate solutions applied for development of a user interface and identify weak points and their impact on usability.

Results of expert evaluation might call for redevelopment of the product’s user interface.

We also apply the method of Comparative expertise enabling to get quantitative evaluation of interface (“better — the same — worse” parameters). However, such method is applicable for testing of similar products.


Usability testing

Enables to measure actual usability of a product and to calculate such indices as Efficiency, Productivity and Satisfaction. This means that usability testing can provide us with rather precise quantitative assessment of your product’s usability attributes.

This method also helps to identify the majority of problem zones and to measure their impact on usability.


Bother methods Expert evaluation and Usability testing must be applied in the course of development of new products in accordance with the “user-centered design” approach (ISO-13407). This approach helps to develop and engineer interfaces with guaranteed excellent usability.


Further: Users and Goals



Users and Goals | Effectiveness | Efficiency | Satisfaction | Methods