Experimental and Observational Designs

Research study design refers to the overall plan or strategy that a researcher uses to conduct a study in order to answer a research question or test a hypothesis. A good study design is essential for ensuring that the research is conducted in a rigorous and systematic manner, and that the results are reliable and valid.

Research studies are often classified in terms of their designs. Here, we will make the distinction between experimental and observational research designs.

There is no difference between “observational design” and “observational study” because they both refer to a type of research study design that involves observing and measuring the behavior or characteristics of a group of participants without manipulating any variables.

Similarly, Experimental research design refers to the overall plan or framework for conducting an experiment. It includes the selection of participants, the manipulation of variables, and the measurement of outcomes.

There are several types of research study designs, including:

1. Experimental design

This type of design involves manipulating one or more variables to determine their effect on another variable. Participants are randomly assigned to either a control group or an experimental group, and the researcher measures the outcome of interest in both groups.

2. Observational design

This type of design involves observing and measuring the behavior or characteristics of a group of participants, without manipulating any variables. Observational designs can be either cross-sectional (measuring at a single point in time) or longitudinal (measuring over time).

Few other research study designs are

• Quasi-experimental design: This design is similar to experimental design, but participants are not randomly assigned to groups. Instead, the researcher selects groups that are already naturally different in some way and compares their outcomes.
• Survey design: This design involves collecting data through questionnaires or interviews with a group of participants.
• Case study design: This design involves in-depth analysis of a single individual, group, or event.
• Meta-analysis: This type of design involves the statistical analysis of data from multiple studies to draw conclusions about the overall effect size of a particular intervention or variable.

Example of Experimental Design:

Suppose a researcher wants to investigate the effect of a new drug on blood pressure. They randomly assign participants into two groups: one group receives the new drug, while the other group receives a placebo. The researcher measures the participants’ blood pressure before and after taking the drug or placebo, and then compares the changes between the two groups to determine whether the new drug has an effect on blood pressure.

Example of Observational Design:

Suppose a researcher wants to investigate the relationship between smoking and lung cancer. They select a group of participants who have been diagnosed with lung cancer and a group of participants who have not been diagnosed with lung cancer. The researcher then asks both groups about their smoking history, and compares the rates of smoking between the two groups to determine whether there is a relationship between smoking and lung cancer. Since the researcher is not manipulating any variables or assigning participants to groups, this is an observational study.