How would you filter a list of many items?

Question

When I go to UX job interviews, I very often get asked this question:

How would you display a big list of many items and many filters / filter criteria?

For example: consider a huge list of items in a mobile OS scenario. Users need to have a tool which would enable quick filtering through the list and find items of interest. There are above 20 different filter criteria.

Answer 1

Firstly it is a poor question to be asked. From Nielsen

Winning app UIs include domain-specific solutions that allow humans to focus on deeper issues while the software takes care of the mechanics. http://www.nngroup.com/articles/best-application-designs/

If you don't know the user domain you won't have a great UI. You can both show astuteness and limit the applicable designs by clarifying:

• Are any criteria more likely to be filtered on than others?
• How many entries per criteria? or are some a scale.
• How much of each item being searched needs to be displayed?
• Is type text to filter useful against item? And against criteria?
• Is there a natural hierarchy at play? (trees, exclusive options)
• Is user visual scan fast or slow (e.g. Flags/Faces vs. text )

The right UI should vary depending on the answers.

Answer 2

Maybe it would be a great idea to display attribute filters with the corresponding column headers, if possible. This can also be achieved when the attributes per combo-filter do not intersect (like a set of column groups with their filters).