Table 1.

Key concepts and terms in quantitative and qualitative methods

DomainQuantitative MethodsQualitative Methods
Types of questionsHow much? How often?What is it like? How does it work? What does it mean?
Data typeNumeric.Non-numeric or naturalistic (e.g., interview audio and transcripts, images, objects, observation notes, documents).
Analytical approachCommonly deductivea, designed to test an existing theory about a phenomenon through hypothesis-based research questions.Commonly inductivea, designed to develop an explanatory theory or conceptual framework directly from the data by posing open-ended research questions.
SamplingTargeted to the number of participants needed to support statistical analyses. Eligibility criteria, sample size, and analytic plan are often prespecified.Targeted to the number of participants needed to support sufficient elucidation of emergent concepts from the data. Participants are purposively selected on the basis of the likelihood that they will be able to offer relevant perspectives on a phenomenon and/or to fill conceptual gaps as an understanding of the phenomenon begins to emerge. Recruitment continues until reaching thematic saturation, or the point at which additional sampling yields little new information.
Applicability beyond research participantsLarge and representative samples support statistical inferences about applicability to the source population independent of the specific details of the study sample. Findings may be externally generalizable if the study population is sufficiently representative of other persons or groups with the condition of interest.The theory or conceptual framework that results from a study may be transferrable to an external context when the study and external settings share core features on which the theory is based.
Limiting biases of the researchersObjectivity is supported by limiting and prespecifying the ways in which the researcher interacts with the data. Results should be reproducible in future studies.A theory or conceptual framework is constructed through the researcher’s (or research team's) interpretation of the data, so results are inherently subjective. Researchers reflect on their own background and experiences that shape results (reflexivity) and report these to help readers contextualize the findings. During analysis, emerging themes are repeatedly compared with original data to ensure that they are grounded in these data. Trustworthiness is enhanced by methodologic features such as member checking, co-coding by researchers with different backgrounds, and triangulation of findings using different methods and in different settings.
  • ↵a The degree of open-endedness of any research activity exists along a spectrum. Some quantitative methods employ inductive approaches and qualitative methods can involve more deductive components.