Part 3 · Where does CNA apply?
Module 5 · Which research questions fit CNA?
Asking a question CNA can actually answer
- Write a research question in the shape CNA can answer.
- Tell a CNA question apart from a regression question.
- Spot when a question is about combinations rather than single effects.
CNA does not answer "by how much does X move coverage." It answers a sharper, more useful question: "which conditions, alone or in combination, make the difference to the outcome." In the words of the method's own literature, CNA hunts for difference-making conditions, the necessary and/or sufficient combinations that an outcome actually depends on. Good CNA questions are always shaped that way, and the best ones point straight at a problem you can fix.
Here are five questions immunization teams genuinely ask, written the way CNA likes them:
| Topic | A CNA-shaped question |
|---|---|
| Coverage | Which combinations of health-system gaps make the difference to low DTP3 coverage? |
| Zero-dose | Which conditions, alone or together, are linked to a high share of zero-dose children? |
| Stockouts | Which combinations of conditions are necessary or sufficient for repeated vaccine stockouts? |
| Supervision | Which weak supervisory practices, in combination, make the difference to poor session quality? |
| Pathways | Through which chain of conditions does weak supervision lead, step by step, to missed children? |
The first four ask which difference-making conditions sit behind an outcome. The fifth is special: it asks about a pathway, a chain where one condition feeds the next. CNA is one of the few methods that can model these multi-step, multi-outcome structures, which is exactly why it suits messy program systems.
Can you phrase it as "which conditions make the difference?"
If your question can be rewritten to ask which conditions, alone or in combination, make the difference to an outcome, it is a CNA question. If it asks for a single number, a ranking, or an average effect, it belongs to a different method, and that is perfectly fine.
The phrase "difference-making conditions" runs throughout the applied CNA literature. See, for example, studies framed explicitly around difference-making roles and pathways in the references at the end of this course.
Take a question your team is currently asking.
- Is it really 'which factor matters most', or 'which combinations make the difference'?
- How would you rewrite it so CNA could answer it?