Quantitative Research

Quantitative versus Qualitative Facts, Claims, and Variables

Research studies, whether they are described as quantitative or qualitative, involve the use of facts, claims, and variables. Facts, claims, and variables that are represented by numbers are regarded as quantitative information. Facts, claims, and variables that are presented in narrative, categorical, or nominal forms are regarded as qualitative information. In most research studies, both qualitative and quantitative information are presented and analyzed. For example, many qualitative studies include numbers to describe phenomena of interest, such as numbers of times particular events occur, time periods or dates that document when an event occurred, or the amount of time devoted to particular activities. Many quantitative studies include qualitative variables in the form of constructs that are the object of study, categories or kinds of phenomena that are being examined, or descriptions of the contexts in which the interventions take place. Thus, the distinction between quantitative and qualitative data and studies may be overdrawn.

Mixed-methods designs are used when it is important to include both qualitative and quantitative data. For example, case studies often use mixed-methods designs and include qualitative data from interviews and focus groups and quantitative data in the form of test scores, counts of behaviors that occur in settings of interest, or summarized survey data.

Overview of Methods Used in Quantitative Research

In conducting quantitative research, several kinds of activities constitute the methodology of the study. The following section identifies and briefly describes these methods; clearly the treatment is not exhaustive and more sources about quantitative research are specified in the Further Readings section.

Two critical activities that a researcher encounters when conducting quantitative research are the identification of the study purpose and the selection of an appropriate research design (e.g., survey, experiment, quasi-experiment). The choice of design is shaped by considerations such as the economy of the design, the strength of the inferences that can be made, and how quickly the results may be available. After selecting a research design, the researcher has to identify the population to be studied and the sampling procedure needed to conduct the study. The sampling procedures required may include determination of the size of the population, the use of a random or convenience sample, use of probability or nonprobability samples, and stratification of the population before selecting the sample. If there will be random assignment of participants to treatment and comparison groups, the researcher must establish the size and comparability of the groups to be compared. As part of planning quantitative research study, the dependent and independent variables must be identified and the instruments used to measure these variables must be developed or purchased. It is advisable to choose “off-the-shelf” instruments with established evidence of reliability and validity. However, if such instruments are not available, it is important to follow a systematic process of instrument design, development, and pilot testing. After the logistics of the data collection are complete, it will be necessary to conduct appropriate statistical analyses of the quantitative data. These analyses might make use of contingency tables, correlational techniques, regressions, analyses of variance and covariance, and more recently use of multilevel analyses, such as hierarchical linear modeling.

...