Quantitative and qualitative research approaches often complement each other—and may even appear similar at first glance. For instance, a questionnaire may be perceived as a qualitative tool, but if it is designed to produce numerical data and statistical analysis, it is considered quantitative. 

Understanding the key distinctions helps clarify how each method contributes to evidence generation in health technology assessment (HTA): 

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Quantitative

Focused on numerical data and statistical analysis 

Category: Objective

Type of reasoning: Deducting reasoning used to synthesise data

Focus: Concise and narrow

Application: Tests theory

Basis of knowing: Cause and effect relationships

Basic element of analysis: Numbers and statistical analysis

Scope: Single reality that can be measured and generalised

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Qualitative

Focused on exploring perspectives, experiences, and meanings 

Category: Subjective

Type of reasoning: Inductive reasoning used to synthesise data

Focus: Complex and broad

Application: Develops theory

Basis of knowing: Meaning, discovery, correlation

Basic element of analysis: Words, narrative

Scope: Multiple realities that are continually changing with individual interpretation

Table 1 Features of quantitative and qualitative research, adapted from (2).

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Mixed methods

Focused on combine quantitative and qualitative data instead of analysing them separately

Research does not have to be entirely qualitative or entirely quantitative. A popular form of research is referred to as ‘mixed methods’ research using both qualitative and quantitative approaches. Researchers combine quantitative and qualitative data instead of analysing them separately.

Although there are many definitions of exactly what constitutes ‘mixed methods’, one popular definition (3) describes it as an approach or methodology that:

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Focuses on research questions that call for real-life contextual understandings, multi-level perspectives, and cultural influences

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Employs rigorous quantitative research assessing magnitude and frequency of constructs and rigorous qualitative research exploring the meaning and understanding of constructs

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Utilises multiple methods (e.g. intervention trials and in-depth interviews)

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Intentionally integrates or combines these methods to draw on the strengths of each

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Frames the investigation within philosophical and theoretical positions.

A checklist for appraising qualitative research trials can be found in Further reading.