PHN 652 Topic 3 DQ 1: Qualitative vs Quantitative

Frame the comparison around questions rather than around methods, because an advantage with no question attached is not an advantage. Quantitative data answers how many, how often, how much and whether a difference is larger than chance. Its advantages follow from that: it aggregates, so a whole population can be characterised; it compares across places and times using the same units; it supports statistical inference; and it is what funders and policymakers ask for. Its disadvantages follow just as directly. It cannot tell you why a number moved, it discards everything that does not fit the categories decided in advance, and it is only as good as the operational definitions behind it — a vaccination rate is a fact about records as much as about vaccinations. Say which of these your own practice question needs before comparing anything, because the comparison reads very differently once a question is on the table.

Qualitative data answers why, how and what it is like. It surfaces explanations nobody anticipated, which is exactly what a fixed questionnaire cannot do, and it is the only way to understand a barrier that the affected community has never been asked about. Its disadvantages are that it does not generalise in the statistical sense, that it is labour-intensive, and that analysis depends on interpretation and therefore on the credibility procedures the analyst can demonstrate. Then give the examples the prompt asks for and make them public health nursing examples. Quantitative: establishing that childhood immunisation coverage in one ZIP code is fifteen points below the county average. Qualitative: finding out why, through interviews with parents who declined, where the answer might be clinic hours rather than vaccine belief. Note that the second study is unaskable until the first has told you where to look. Name the credibility procedures you would expect to see in a defensible qualitative study.