Qualitative data is most commonly collected in cases where the researcher is studying social topics or issues that are affected by human experience. Researchers cannot get adequate or appropriate information for these projects from numbers because numbers do not provide understanding of human thought, interaction or experience. For example, a researcher studying how religious beliefs affect an individual's political leanings would likely benefit from using qualitative research methods. In contrast, quantitative research is primarily used for studies that focus on cause and effect relationships or to find out if one variable influences another in a controlled environment. Studies on the effect of a medication on a particular medical condition would require quantitative data.
Qualitative data can be collected in several ways. These include questionnaires, interviews and observations. Because researchers working on a qualitative study aim to understand events within the natural, human experience they occur in, they value open-ended responses from participants. Quantitative data, however, is collected in a controlled environment; the goal is to prevent human behavior from affecting or influencing findings. Data is collected in planned, controlled experiments.
The method of collection obviously affects the type of data that is gathered. In qualitative research, data is usually in words or images; the researcher's personal observations and the open-ended responses from participants provide the information needed to find relationships or correlations. Quantitative research, on the other hand, results in measured data in number form. Data in a study on how a beta-blocker drug affects the heart, for instance, may include participants' blood pressure readings and heart rates.
All research reports identify background information, the research question, the purpose of the study, the methods of collection and the findings. This information is essential for peer review. How the data is presented, however, depends on the type of research performed. Qualitative study reports provide firsthand accounts of the researcher's observations and often provide anecdotes from study participants. In contrast, reports on studies requiring quantitative data collection contain a significant amount of numerical and statistical data, which is often presented in table or chart form.