The four most commonly used designs for research studies are descriptive, correlational, quasi- experimenal, and experimental.”(Grove, Gray & Burns, 2015). Descriptive and correlational designs can be referred to as non-experimental designs because the focus is on examining variables as they naturally occur in environments and not in the implementation of a treatment by the researcher.
In experimental design researchers uses random assignment and they manipulate an independent variable around a controlled variable. A true experimental design there must be randomization, a control group and manipulation of a variable when examining the direct cause or predicted relationships between variables. In a quasi-experiment one of these aspects is missing.(Sousa, Driessnack & Menders, 2007).
A non experimental research design focuses on examining variables as they would naturally occur, types of nonexperimental research designs are: survey, case studies, correlation studies, comparative studies and descriptive studies. Non experimental designs have no random assignments, no control groups and no manipulation of variables, the research design is observation only.(Sousa, Driessnack & Menders,
Experimental research is the most powerful quantitative method. It has a rigourous control of the variables. It is an objective, systematic, and highly controlled investigation conducted for predicting and controlling phenomena (Grove, 2017). During the experimental design, the researcher uses random assignment. They also manipulate an independent variable around a controlled variable. In a true experimental design, there must be randomization, a control group, and manipulation of a variable while examining the direct cause or predicted relationships between variables.
Non-experimental research is research that lacks the manipulation of an independent variable, random assignment of participants to conditions or orders of conditions or both. It focuses on examining variables as they would naturally occur. Some of the examples of the experimental research are: survey, case studies, comparative studies, and descriptive studies. This type of research has no random assignments, no control groups, and no manipulation of variables. The research method is observation only.
Experimental research provides convincing evidence that changes with an independent variable. Thus, it results in the differences in a dependent variable. On the other hand, non-experimental research does not cause any changes in the independent variable