StATS: What is qualitative data?

There are two separate definitions of this term. Some people use the term "qualitative data" to represent categorical data.

Other people use the term to represent verbal or narrative pieces of data. These types of data are collected through focus groups, interviews, opened ended questionnaire items, and other less structured situations.

Qualitative research is not the same as anecdotal information. Qualitative research is rigorous research with

explicit sampling strategies, systematic analysis of data, and a commitment to examining counter explanations. Ideally, methods should be transparent, allowing the reader to assess the validity and the extent to which results might be applicable to their own clinical practice. -- BMJ 1998; 316:1230-1232.

Denise Polit gives a delightful example of the difference between qualitative and quantitative data in her book Data Analysis and Statistics for Nursing Research.

Here is her example of qualitative data.

Have you felt sad or depressed at all lately, or have you generally been in good spirits?

(Subject 1) Well, I’ve been in pretty rough shape lately, to tell you the truth. I mean, I haven’t felt suicidal or anything like that, but I just can’t seem to shake the blues. I just don’t see anything to feel hopeful about in my future. I haven’t really had anybody to talk to about my problems since my husband died last year.

(Subject 2) I’m not at all depressed. I feel great! I love my new job. And I’ve lost 20 pounds and feel much healthier than I have in years. I can’t remember any period of my life when I’ve been happier.

Here is her example of quantitative data.

Quantitative: Thinking about the past week, how depressed would you say you have been on a scale from 0 to 10, where 0 means "not at all" and 10 means "the most possible?"

(Subject 1) 9

(Subject 2) 0

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