The goal of a research study is to answer a question. This question addresses a phenomenon or an intervention and the effects on a specific population. An experimental research study design attempts to determine a causal relation between an independent variable, the intervention, and the dependent variable, the result. A nonexperimental study design attempts to answer the question through observation and measurements in which the researcher does not actively manipulate anything.

Comparative Research Design

Comparative research studies essentially compare two different groups. These studies may be experimental or nonexperimental. Comparative studies often attempt to draw conclusions across nationalities or social groups, and they often include socioeconomic and demographic variables. The purpose of these studies is to determine either similarities between groups or differences between groups. A comparative study may look at the effects of an intervention on students of two different ethnicities, or the effects on low-income students versus high-income students. Data from comparative studies are analyzed for revelations about these two groups.

Qualitative Research Design

The qualitative research design is based primarily on observation. The researcher attempts to develop a theory about a group or population by collecting and analyzing observational data. This data may be categorized and measured, but the researcher does not manipulate it. Case studies involve collecting data surrounding the effects of a situation or environment on an individual, and the researcher does not change or alter that situation in any way. This study design is used when studying cultural groups, individuals or a specific grouping, such as a grade level.

Quantitative Research Design

A quantitative research design is experimental. The researcher designing a quantitative study begins with a specific research question targeting a specific population and a specific independent variable, or intervention. For example, a research question that would be answered using a quantitative study may address the effects of a math intervention on elementary-school students in urban schools. The population sample is chosen at random, and the researcher manipulates the intervention to record the effects.

Examples of quantitative research designs are pretest - posttest design, in which the effects are measured before and after the intervention, or a control group design, in which the researcher divides participants randomly into two groups and implements the intervention in one and a placebo in the other.

Exploratory Design

An exploratory design is used when there are few studies about the given topic. These studies provide general information and include small population samples. Exploratory studies are often used to gather enough information to design a larger study and are foundational to building theories and anticipating possible obstacles or setbacks for future research. Because these studies are small and often vague, they are inconclusive and cannot be used to determine a causal relation. However, they are essential to designing future studies.