A variety of methods and designs can be used in criminal justice research. Both qualitative and quantitative methods are valid approaches to the sociological questions researchers will have when faced with presenting problems and issues. Ideally, criminal justice research should remain relevant, grounded in theory, and applicable to public policy or practice. Criminal justice policies and procedures can and should be evidence-based. Scientific research helps to identify which interventions or policies work, and which do not, based on quantitative data or on phenomenological factors like public opinion. The two main branches of social science research include qualitative and quantitative designs. Qualitative research is not necessarily inferior to quantitative research in the social sciences because measurable outcomes cannot account for all aspects of the human experience. Therefore, researchers will often use qualitative methods like in-depth interviews, case studies, and focus groups in order to gather information, ask open-ended questions, and ascertain variables that can later be tested more empirically. Qualitative research can therefore become the forerunner to quantitative research. Many criminal justice researchers also opt for mixed methods or multimethod approaches, which allow for the integration of data from both types of studies (Maxwell, Chmiel & Rogers, 2016). Unlike quantitative research, qualitative research is driven by questions and not hypotheses, and does not purport to establish causal or even correlative connections between variables. Quantitative research is based on the scientific method.

Components of criminal justice research that are shared in common among both qualitative and quantitative research methods include the necessity of defining terms (operationalizing), outlining the gaps in the literature or motivation for the current research, and explaining the researcher’s theoretical orientation. Research often follows from theory, but research can also inform or enhance existing criminal justice theory. Likewise, researchers need to explain why they selected the type of design and methodology used in the study whether it is qualitative and quantitative research. Issues related to reliability and validity are as important in qualitative as in quantitative research in the social sciences.

Quantitative research follows the five steps of the scientific method, regardless of research design. The five steps of the scientific method include the making of observations, the formulation...

Taken together, these five steps form the backbone of any scientific research, including research that addresses topics pertinent to criminology and criminal justice. However, there are many different kinds of quantitative research designs that can be used. The criminal justice researcher selects a specific type of research design not on a whim or personal preference, but based on the nature of the research questions and hypotheses. Some hypotheses lend themselves to experimental designs, but not all research questions can be tested using experimental methods.
Criminal justice researchers use numerous types of experimental research designs including true experiments that are the gold standard in the social sciences. True experiments involve both random population selection and random assignment, and ideally large enough sample sizes. An experimental research design establishes causality between the independent and dependent variable by controlling strictly for any extraneous variables that could impact the reliability or validity of the study (“Quantitative Approaches,” n.d.). For example, a criminal justice researcher might study the effect of a drug treatment program on reducing recidivism rates in the community. The independent variable is the condition of either taking or not taking the drug treatment program, and the dependent variable would be recidivism, measured using specific instruments. With experimental and other quantitative research, the researchers need to carefully clarify the tools and instruments they are using, clarify why those tools or measures are accurate and relevant, and then report results both in terms of raw data and statistical analyses.

When true experimental methods are not possible, researchers in criminal justice have other options. One option is a quasi-experimental design. A quasi-experimental design may be warranted if the researcher cannot adequately manipulate the independent variable, which is common in real world criminal justice settings. Also, a quasi-experimental research design is indicated when the researchers cannot perform random assignment. Quasi-experimental designs can still be used to determine cause and effect using statistical analysis of data. For example, the…