The statistical mean or average value does not reflect reality. The reason for this lies in probability: the mean value is formed from a large number of individual values, which usually differ considerably from one another. The mathematical probability that an individual value will match the average value is extremely low. Although there is a small probability, even if it were to occur, these values would always be in an extreme minority.

To put it a little bluntly, normality is actually the extreme case and deviation is the norm.

This raises the question of whether it makes sense to refer to mean values when making assessments or decisions. Wouldn't it be more appropriate to focus more on the deviations, since they ultimately make up the majority?

Application in UX and UI design

In UX/UI design, this principle means that there is no such thing as an "average" or "normal" user, but only users who deviate either upwards or downwards.

Therefore, you should always consider the different (possibly extremely divergent) behaviors and needs of users, not just those of the average user. A design is only «inclusive» and «universal» if it is flexible enough to cover a wide range of user needs.

Neurodiversity

Even in the context of neuroscience, an orientation towards the middle is not useful. The natural differences in the human brain, including the differences in the way people process information and interact with their environment, suggest that this diversity is intended by nature and evolution and makes perfect sense. Diversity and deviation from the norm is a concept in biology that ensures our survival. In borderline situations, it is the deviants and extremes that survive, not the stochastic mean.

Statistical principles

'Normal' and 'extreme' are just two terms that refer to the statistical distribution of a phenomenon, namely that every person, user, customer is different. The behavior or characteristics that are in the center of the range are generally described as 'normal', and the behavior or characteristics that are at the edges are described as 'extreme'. However, they say nothing about their frequency, either relative or absolute.

Gaussian distribution

With the «Gaussian distribution», a bell shape does form around the mean (see figure above), but there is also a large proportion of deviating values to the right and left of it, which play a major role in the sense of inclusion or a comprehensive solution.

Furthermore, not all distributions are structured in this way (see figure below). Often, so-called bi- or multimodal distributions are present, which show two or more peaks. In these cases, their mean lies outside the peaks and does not represent the majority.

 

The average or mean value says nothing about the actual frequency distribution.

The average or mean value says nothing about the actual frequency distribution.

 

That is why the concept of Designing for the Extremes has been established as part of the Design Thinking methodology developed at the d.school at Stanford University. This principle emphasizes the economic importance of designing products and services for extreme users or usage scenarios as well. By focusing primarily on "average" users or customers, companies are missing out on significant market potential and valuable revenue opportunities.

As the well-known "Click-Away Pound Report 2019" shows, 69% of users with disabilities leave websites that are difficult for them to access and never return to them. This results in a loss of £17.1 billion in sales for British retailers every year.

Universal Design

These findings, and above all the motivation to avoid excluding people from a solution if at all possible, led a group of designers and architects at North Carolina State University in the 1980s to develop an approach to design that was as inclusive as possible, which they called Universal Design. It consists of seven principles and aims to design products, services and environments so that they can be used by as many people as possible, regardless of age, gender, abilities or cultural background.

Universal Design goes beyond accessibility by considering the diversity of user needs from the outset and creating products that can be used for rare or non-standard applications.

Impact on the User Experience

strong

Further information