Substance Abuse & Mental Health Services Administration

The Substance Abuse and Mental Health Services Administration (SAMHSA)

Epidemiological Data: What Can it Tell You?

Quantitative and Qualitative Data

Quantitative data is described in numbers and shows how often something occurs or to what degree a phenomenon exists. Quantitative data: 

  • Answers, “How many?” “How often?”
  • Measures levels of behavior and trends.
  • Is objective, standardized, and easily analyzed.
  • Is easily comparable to similar data from other communities and levels. 
  • Examples: statistics, survey data, records, archival data.

Qualitative data is described in words and explains why people behave or feel the way they do. Qualitative data: 

  • Answers, “Why?” “Why not?” or “What does it mean?”
  • Allows insight into behavior, trends, and perceptions. 
  • Is subjective and explanatory.
  • Helps interpret quantitative data, provides depth of understanding.
  • Examples: focus groups, key informant interviews, case studies, story-telling, observation.

Communities may not have quantitative data, particularly for certain at-risk groups (e.g., homeless, LBGT, and some minority groups like tribes); so qualitative data can be very useful in these situations. In fact, many epidemiologists and evaluators recommend collecting both quantitative and qualitative data.  This “mixed method” provides a much more in-depth understanding of the population groups or communities being assessed because it allows you to collect the same information across several individuals/groups (or other units of measure). In addition, usually the quantitative data generates responses to questions that are created by the researcher, whereas the qualitative is more open-ended with responses that are generated by the respondents; so combining the two approaches offers a way to understand the quantitative data from the perspective of the respondent.