A quantitative research project is characterized by having a population for which the researcher wants to draw conclusions, but it is not possible to collect data on the entire population. For an observational study, it is necessary to select a proper, statistical random sample and to use methods of statistical inference to draw conclusions about the population. For an experimental study, it is necessary to have a random assignment of subjects to experimental and control groups in order to use methods of statistical inference.
Statistical methods are used in all three stages of a quantitative research project. For observational studies, the data are collected using statistical sampling theory. Then, the sample data are analyzed using descriptive statistical analysis. Finally, generalizations are made from the sample data to the entire population using statistical inference. For experimental studies, the subjects are allocated to experimental and control group using randomizing methods. Then, the experimental data are analyzed using descriptive statistical analysis. Finally, just as for observational data, generalizations are made to a larger population. Iversen, G. (2004). Quantitative research. In M. Lewis-Beck, A. Bryman, & T. Liao (Eds.), Encyclopedia of social science research methods. (pp. 897-898). Thousand Oaks, CA: SAGE Publications, Inc.
Qualitative research is defined as any type of research "that employs non-numeric information to explore individual or group characteristics, producing findings not arrived at by statistical procedures or other quantitative means. Examples of the types of qualitative research include clinical case studies, narrative studies of behaviour, ethnography, and organizational or social studies."^{4} Qualitative research is useful for understanding an area where little is known, or where previous work seems to be inadequate or not applicable to a particular situation. Qualitative research is explanatory: it seeks to make sense of complex situations where reducing the data to quantifiable elements would cause the loss of too much information. Hence its sampling methods focus on sampling content, rather than persons. It shows how particular situations are experienced and interpreted. Qualitative methods are useful in constructing a theory or a theoretical framework from observable reality and in understanding phenomena deeply and in detail. The precise research question dictates the qualitative data collection and analytic methods to be used.
"Qualitative Research.” AFMC Primer on Population Health, The Association of Faculties of Medicine of Canada Public Health Educators’ Network,http://phprimer.afmc.ca/Part2-MethodsStudyingHealth/Chapter5AssessingEvidenceAndInformation/Qualitativeresearch (Accessed Feb. 27, 2015). License: Creative Common http://phps BY-NC-SA