Need help regarding filter logic

Question

I've noticed two different possible behaviours for checkbox filters and I was wondering if anyone could shed some light on how one should deal with these cases as a designer.

Case 1: SHOES > COLOR > [x]red, [x]blue, [ ]yellow. This should show you all blue and all red shoes.

Case 2: Rooms > Amenities > [x]wifi, [x]balcony, [ ]breakfast Now in this case we want wo see all rooms that have both wifi and a balcony

In case 1 you are seeing more results with each selected checkbox, while in case 2 its the other way round. Yet the interface looks exactly the same. How do I contend with this? Do we just assume what the users expectations are for the given context and design the logic as such?

Answer 1

When it comes to the design of filters, the users' expectation do not always align with the logic design. According to a research by Baymad, underlying filtering logic found at 32% of e-commerce sites downright misaligns with users’ expectations of how filters work, and how users even look for and evaluate products online.

So when it comes to eCommerce: Case 1 > Case 2 i.e You should allow users to combine multiple filtering values of the same type.

These were the general outcomes of their research:

To help users get highly refined product lists

Allow users to combine multiple values of the same filter type
Use an “AND” logic for filter types and an “OR” logic for filter values
Style filter values as checkboxes

Answer 2

Context helps the user navigate these scenarios. In Case 1, the user knows that color is an "Or" filter because shoes are not likely to be both red and blue. In case 2, the user knows it's an "And" filter because a hotel room can easily have both wifi and and a balcony.

You can strengthen these to be even more intuitive with additional signifiers. For example, the hotel website could start with the number of hotels that are available with no filtering, and reduce the amount every time a filter is checked, letting the user know that they're narrowing their results.

Discoverable help text can also provide more context if the category isn't obviously an "and" or an "or".