Filtering by checking multiple boxes is not consistent

[jillpe]

Summary

User Feedback:
Noted that filtering by checking more than one box seems to work as an AND in for some categories (Subject and Keyword) and an OR in others (Types and Levels).

VIVA Goal:
Within a facet it should be "OR" and between facets should be "AND" So for example the user who selects "Nursing" from Subjects and "Anxiety" from Keywords and "Matching" and "Essay" from Types would get all Essay and Matching questions about Anxiety from Nursing.

Acceptance Criteria

• When I select multiple facets (e.g. Subject and Type) we should ... AND those two sets? So we'd have (S1 ∪ S2) ∩ (T1 ∪ T2 ∪ T3) where ∪ is UNION (e.g. “OR”) and ∩ is INTERSECTION (e.g. “AND”).

[jeremyf]

I have reviewed the SQL and the current state of queries is as described in the acceptance criteria.

Which means that we need to get a specific scenario/use case that they are encountering.