What is Non-experimental research?

 (Also called as Descriptive Research or Observational Research)

 Definition: A descriptive study or non- experimental research design is one in which information is collected without changing the environment (i.e., nothing is manipulated). it is a type of investigation in which the researcher has no control over the variables of the experiment. Non-experimental research focuses more on observation rather than on conducting actual experiments. 

For example, looking over the purchase history of the customers on a website to figure out the demand and supply for a particular commodity. In non-experimental research, researchers measure variables as they naturally occur without any further manipulation. This type of research is often referred to as observational research or descriptive research, to reflect the idea that phenomena are observed rather than manipulated. 

Descriptive studies, in which the researcher interacts with the participant, may involve surveys or interviews to collect the necessary information. Descriptive studies in which the researcher does not interact with the participant include observational studies of people in an environment (e.g., observing the trend in the markets) and studies involving data collection using existing records (e.g., medical record review).

 Non-experimental research is based on the observation of phenomena in their natural environment. In this way, they can be studied later to reach a conclusion. [1] 

Characteristics of non-experimental research: [2]

• Most studies are based on events that occurred previously and are analyzed later. 

• In this method, controlled experiments are not performed for reasons such as ethics or morality.

 • No study samples are created; on the contrary, the sample or participants already exist and develop in their environment.

• The researcher does not intervene directly in the environment of the sample.

• This method studies the phenomena exactly as they occurred. 

• Non-experimental research can be both quantitative and qualitative.

This type of research is used when the researcher has no specific research question about a causal relationship between 2 different variables, and manipulation of the independent variable is impossible. 

They are also used when: 

• subjects cannot be randomly assigned to conditions. 

• the research subject is about a causal relationship, but the independent variable cannot be manipulated. • the research is broad and exploratory 

• the research pertains to a non-causal relationship between variables.

• limited information can be accessed about the research subject. 

Types of Non-experimental research 

There are 3 main types of non-experimental research:

Cross-sectional Research

Cross-sectional research involves the comparison of two or more preexisting groups of people under the same criteria. This approach is classified as non-experimental because the groups are not randomly selected and the independent variable is not manipulated. For example, an academic institution may want to reward its first-class students with a scholarship for their academic excellence. Therefore, each faculty places students in the eligible and ineligible group according to their class of degree. In this case, the student’s class of degree cannot be manipulated to qualify him or her for a scholarship because it is an unethical thing to do. Therefore, the placement is cross-sectional. [2]

Correlational Research

 Correlational type of research compares the statistical relationship between two variables. Correlational research is classified as nonexperimental because it does not manipulate the independent variables. For example, a researcher may wish to investigate the relationship between the class of family students come from and their grades in school. A questionnaire may be given to students to know the average income of their family, then compare it with CGPAs. The researcher will discover whether these two factors are positively correlated, negatively corrected, or have zero correlation at the end of the research.[2]

 Observational Research

Observational research focuses on observing the behavior of a research subject in a natural or laboratory setting. It is classified as nonexperimental because it does not involve the manipulation of independent variables. A good example of observational research is an investigation of the crowd effect or psychology in a particular group of people. Imagine a situation where there are 2 ATMs at a place, and only one of the ATMs is filled with a queue, while the other is abandoned. The crowd effect infers that the majority of newcomers will also abandon the other ATM. You will notice that each of this non-experimental research is descriptive in nature. It then suffices to say that descriptive research is an example of non-experimental research. [2]

What is Experimental Research? 

Definition: An experiment is a study in which a treatment, procedure, or program is intentionally introduced, and a result or outcome is observed.

 Experimental research is the type of research that uses a scientific approach towards manipulating one or more control variables of the research subject(s) and measuring the effect of this manipulation on the subject. It is known for the fact that it allows the manipulation of control variables. 

Unlike a descriptive study, an experiment is a study in which a treatment, procedure, or program is intentionally introduced, and a result or outcome is observed. 

True experiments have four elements: manipulation, control, random assignment, and random selection. The most important of these elements are manipulation and control. Manipulation means that something is purposefully changed by the researcher in the environment. Control is used to prevent outside factors from influencing the study outcome. When something is manipulated and controlled and then the outcome happens, it makes us more confident that the manipulation "caused" the outcome. Another key element of a true experiment is random assignment. Random assignment means that if there are groups or treatments in the experiment, participants are assigned to these groups or treatments, or randomly (like the flip of a coin). This means that no matter who the participant is, he/she has an equal chance of getting into all of the groups or treatments in an experiment. This process helps to ensure that the groups or treatments are similar at the beginning of the study so that there is more confidence that the manipulation (group or treatment) "caused" the outcome.

 Experimental research is usually undertaken when the goal of the research is to trace cause-and-effect relationships between defined variables. However, the type of experimental research chosen has a significant influence on the results of the experiment. [3]

Types of Experimental Research 

There are 3 main types of experimental research namely, pre-experimental, quasi-experimental, and true experimental research [4]

Pre-experimental Research 

Pre-experimental research is the simplest form of research and is carried out by observing a group or groups of dependent variables after the treatment of an independent variable which is presumed to cause change on the group(s). It is further divided into three types. 

Pre-experimental research is the simplest form of research and is carried out by observing a group or groups of dependent variables after the treatment of an independent variable which is presumed to cause change on the group(s). It is further divided into three types. 

One-shot case study research: A research design in which a single group is observed on a single occasion after experiencing some event, treatment, or intervention. The carefully studied single instance is compared to general expectations of what the case would have looked like had the treatment not occurred and to other events casually observed. o Because there is no control group against which to make comparisons, it is a weak design; any changes noted are merely presumed to have been caused by the event 

One-group pretest-posttest research: In this type of research design a single case is observed at two time points, one before the treatment and one after the treatment. Changes in the outcome of interest are presumed to be the result of the intervention or treatment. No control or comparison group is employed. This type of research design is the weakest off all the experimental o The objective is to evaluate the effect of that intervention which can be, training program, a policy change or a medical treatment etc. The one-group pretest-posttest design has 3 major characteristics: 

•  1. The group of participants who receives the intervention is selected in a non-random way.

•  2. The absence of a control group against which the outcome can be compared.

•  3. The effect of the intervention is measured by comparing the pre and post-intervention measurements (the null hypothesis is that the intervention has no effect, i.e., the 2 measurements are equal) 

Static-group comparison: The static-group comparison design is a type of experimental design in which the outcome of interest is measured only once, after exposing a non-random group of participants to a treatment and compared to a control group. The objective is to evaluate the effect of this treatment (or intervention) which can be a medical intervention, a training program, a policy change.

 This design has 3 major characteristics: 

• Participants are NOT randomly assigned to either receive the intervention or not. 

•  The treatment and control groups are measured at the same time 

• No measurements are taken before the intervention 

The static-group comparison design is one step better than the one-group posttest only design which has 1 posttest measurement only and no control group. 

Quasi-experimental Research

 The Quasi type of experimental research is similar to true experimental research but uses carefully selected rather than randomized subjects. 

The following are characteristics of quasi-experimental research: 

• Time series

•  It involves purposeful manipulation of the subjects by the investigators. 

•  No equivalent control group design- There is a lack of second group or random assignment

True Experimental Research 

True experimental research is the most accurate type, and may simply be called experimental research. It manipulates a control group towards a group of randomly selected subjects and records the effect of this manipulation. Uses at least two groups with random assignment. 

Randomized Clinical Trial (RCT) is considered the “gold standard” of experimental designs, typically involving the controlled comparison of an experimental intervention and a placebo. 

Pros of True Experimental Research 

• Researchers can have control over variables.

•  It can be combined with other research methods.

•   The research process is usually well structured. 

• It provides specific conclusions. 

• The results of experimental research can be easily duplicated. 

Cons of True Experimental Research

• •  It is highly prone to human error. 

  • Exerting control over extraneous variables may lead to the personal bias of the researcher. 

  • It is time-consuming. 

  • It is expensive. 

  • Manipulating control variables may have ethical implications.  

[1] From Portney L and Watkins M, Foundations of Clinical Research: Applications to Practice, 2nd Edition, Pages12-15

[2] Experimental Vs Non-Experimental Research: 15 Key Differences (formpl.us) 

[3] Module 2: Research Design - Section 2 | ORI - The Office of Research Integrity (hhs.gov) 

[4] Experimental Research: Definition, Types and Examples | Indeed.com