Best Practices for Data Visualisation: Part 1

Business Intelligence tools provide lots of ways to summarise and aggregate data, however this alone does not mean that the audience will interpret, understand and gain value from it. Only from careful design and planning can report developers and system designers structure the output in a meaningful and value added way.

To enable me to be able to sell others on design ideas and concepts, I needed to understand more about what I saw, how I interpreted data and what I saw as errors.  My research showed me that these were not new concepts and had previously been applied to paper based items not dynamic or interactive screens, which we mostly work with today.

There were 3 concepts which stood out, the first of which is human memory limits:

Memory Limits:

There are 3 types of memory limits, Iconic, Short Term and Long Term.  The important ones for BI developers are iconic and short term.

Iconic memory is very much like a computer memory buffer, where items are held before they are processed – what goes on here is pre-conscious. If we group items (either by size, shape or colour etc) it can help users process the information in iconic memory, called pre-attentive processing.

Short Term memory is the key limitation in human cognition, studies have proved that we can only store 3-9 chunks of visual information at one time in short term memory.  We can help users perceptions here by grouping items and intelligently using charts.

The key for designers is to reduce the short term memory load by using familiar items, objects, actions and directions.

Data Encoding

The key here is how we can visually encode data for faster perception, it’s better for pre-attentive processing to occur rather than attentive processing which is sequential and therefore takes longer. The best example is trying to find how many 4s are in the following string:


It’s difficult and slow and there’s nothing to distinguish the 4s from the other numbers, in the example below we make them stand out: 


Much easier!  That’s all for this episode, catch the next instalment soon.

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