A team studying nurse burnout runs a mixed-methods project. Order the stages, from the broadest measurement to the deepest understanding.

1. Survey 800 nurses across twelve hospitals with a validated burnout scale.
2. Identify which wards score far above and far below the average.
3. Interview twenty nurses drawn from those extreme wards at length.
4. Analyse the transcripts for themes the survey never thought to ask about.
5. Use those themes to write better survey items for the next round.

This is the explanatory sequential design: measure broadly, then go deep where the numbers point. The survey establishes how common burnout is and where it concentrates - neither of which twenty interviews could tell you - and the interviews recover what a five-point scale cannot, which is what the exhaustion consists of and why these wards differ.

The final step is the one people leave out, and it is what makes the two halves a single project rather than two studies stapled together. Themes that emerged from the transcripts become items in the next questionnaire, so the qualitative work feeds back into what the quantitative instrument is capable of asking.

The order is not the only possible one. An exploratory design runs the other way: interviews first, when you do not yet know enough to write a sensible survey, and the measurement follows. Which order fits depends on whether your uncertainty is about how much or about what.