3/17/2025 Randomised Control
Trial Experimental
Method
Pratignya Das
Introduc on:
Research is a systema c process of collec ng, organizing, and analysing data
to support decision-making. It can be divided into various types, such as crea ng
a new weapon for tac cal advantage or determining the root cause of an area's
rising crime rate. The research design involves making crucial choices, such as
addressing research ques ons, choosing a theore cal framework, measuring
constructs reliably and accurately, selec ng subjects to observe, determining the
number of subjects to sample, and using appropriate data analy c techniques.
These challenges are applicable to all types of research, including exploratory,
experimental, descrip ve, and evalua on research. This paper aims to define the
terms "Experimental Research," "Design-Types," and "Process."
1.(a) What is experimental research design ?
A- Experimental design is a scien fic method that involves altering one or more
independent variables to determine their influence on dependent variables. This
controlled fashion allows for the maximum precision and specific conclusions
regarding a hypothesis statement. The researcher maintains control over all
factors that may affect the result of the experiment, aiming to predict what may
occur. This design is commonly used in sta s cs to describe informa on-
gathering experiments where varia on is present or not, and is executed under
the researcher's complete control. The experimental unit may consist of people,
plants, animals, or other subjects, with two groups of subjects. The goal is to
maximize the dependability of the results by minimizing the impacts of the
variable. Experimental research is a scien fic method that uses two sets of
variables to measure differences. It is used to gather data necessary for be er
decision-making, such as quan ta ve research methods. This research is crucial
for determining facts and ensuring the validity of the findings.
The experimental group is a group that undergoes a specific
treatment, program, or intervention of interest.
The control group is a group of individuals chosen for an
experiment, characterized by a set of diverse circumstances, known
as the independent, experimental, or treatment variable.
(b) How is it different from non-experimental design ?
A- Non-experimental research involves observing variables in their natural state,
without manipulating them. The researcher observes and measures these
variables as they naturally occur in the population, without having complete
control over them. This approach differs from experimental research, where the
researcher has complete control over the independent variable and can
manipulate it to test the hypothesis. In non-experimental research, the
researcher relies on observations and measurements of naturally occurring
variables. Additionally, non-experimental research does not establish a causal
relationship between variables, as other variables may influence the outcome,
unlike experimental research where a high degree of control is necessary to
eliminate alternative explanations for the change in the dependent variable.
(c) What is a randomized control trial (RCT) research design ?
A- Randomized controlled trials (RCT) are prospective studies that measure the
effectiveness of a new intervention or treatment. They reduce bias and provide
a rigorous tool to examine cause-effect relationships between an intervention
and outcome. Randomization balances participant characteristics between
groups, allowing attribution of differences in outcome to the study intervention.
Researchers must carefully select the population, interventions, and outcomes
of interest, calculate the number of participants needed for a relationship, and
recruit participants randomly assigned to either the intervention or comparator
group. This is known as concealment, often achieved through automated
randomization systems. RCTs are often blinded to minimize bias. RCTs can be
analyzed using intention-to-treat analysis (ITT), per protocol, or other variations.
All RCTs should have pre-specified primary outcomes, be registered with a
clinical trials database, and have appropriate ethical approvals. However, RCTs
can have drawbacks, such as high costs, generalisability issues, and loss of
follow-up. Overall, RCTs are essential for understanding the effectiveness of new
interventions and treatments.
2. How RCT is different from natural experiment research
design ?
A- Research-controlled trials (RCTs) involve full control over par cipant
assignment to different groups, ensuring similarity at the start of the study. The
purpose is to establish a causal rela onship between an interven on and
outcome, minimizing bias and confounding factors. However, ethical
considera ons can be challenging, as they may involve withholding poten ally
beneficial treatments from a group, such as in clinical trials comparing
medica on effec veness for a specific disease. Natural experiment studies (NES)
combine features of experiments and non-experiments. They differ from
planned experiments, such as randomized controlled trials, in that exposure
alloca on is not controlled by researchers.
(a) Explain Natural experiment research design ?
A- A natural experiment is a methodological tool used to evaluate the impact of
an interven on when it is implemented without the control of researchers. It
occurs when an interven on is implemented without any manipula on, such as
an environmental structural change, a new program, or a policy change. The
implementa on of a natural experiment is not dependent on whether there is a
plan to evaluate the interven on, and random alloca on of the interven on is
not feasible for ethical or poli cal reasons. Natural experimental studies come
in both tradi onal and non-experimental designs, and the design used depends
on the type of data available during the experiment. Researchers should strive
to use the most robust design possible within a natural experimental study, as
each design conveys unique strengths and limita ons for making inferences
about the rela onship between the interven on and the outcome of interest.
(b) Merits and Demerits of Natural Experiment research
design ?
A- Merits: Natural experiments offer researchers the advantage of studying the
effects of independent variables (IVs) that are impossible or unethical to
manipulate in a controlled se ng. They also provide high external validity, as the
results are more likely to apply to other real-life groups and situa ons, as the IVs
arise naturally from real-life circumstances.
Demerits: Natural experiments are considered non-true experiments because
they do not manipulate the independent variable (IV), which allows researchers
to control extraneous variables or randomly assign par cipants to condi ons.
For instance, Hodges and Tizard's study on ins tu onalized children, which
involved three naturally occurring variables: returning home, staying at the
ins tu on, or being adopted, found that adopted children performed be er
than other groups. However, ethical concerns prevented researchers from
determining whether adop on can overcome priva on. Factors such as
children's demean or behaviour could also influence adop on decisions.
Addi onally, the IV is not manipulated, requiring researchers to study the
condi ons as they occur naturally, resul ng in lower internal validity and
difficulty in drawing confident conclusions about cause and effect. The use of
retrospec ve data for other purposes may introduce inaccuracies,
incompleteness, or difficul es in access, making some people ques on the
validity of natural experiments.
(c) How RCT is different from Natural experiment research
design?
A- RCT: Randomized controlled trials (RCTs) allow researchers to control who
receives an interven on, minimizing bias and strengthening causal inferences.
However, these trials can be ethically challenging or imprac cal in certain
situa ons, such as when withholding poten ally beneficial interven ons from
some par cipants. For example, a study tes ng the effec veness of a new drug
for a specific disease involves par cipants randomly assigned to receive either
the drug or a placebo.
Natural experiment: Researchers use natural experiments to observe natural
events and situa ons, allowing them to observe differences in exposure or
interven on without manipula ng the exposure themselves. These experiments
provide valuable insights but are more suscep ble to bias due to differences in
comparison groups. They can be a useful alterna ve when RCTs are not feasible
or ethical, such as studying the impact of interven ons or exposures in real-
world se ngs, such as comparing crime rates in different areas.
3. Different types of RCT with examples
A- Parallel-group - each par cipant is randomly assigned to a group, and all the
par cipants in the group receive an interven on.
Ex- A study comparing a new drug (interven on) to a placebo (control) for
trea ng a specific disease, where par cipants are randomly assigned to either
receive the drug or the placebo.
Crossover- over me, each par cipant receives (or does not receive) an
interven on in a random sequence.
Ex- Each par cipant receives both the interven on and the control (or placebo)
in a random sequence, with a washout period in between to ensure the effects
of the first interven on have dissipated.
Cluster- pre-exis ng groups of par cipants (e.g., villages, schools) are randomly
selected to receive (or not receive) an interven on.
Ex- A study evalua ng the effec veness of a new school-based program to
improve student reading skills, where en re schools are randomly assigned to
either receive the program or con nue with their current prac ces.
Factorial - each par cipant is randomly assigned to a group that receives a
par cular combina on of interven ons or non-interven ons.
Ex- A study inves ga ng the combined effect of a new medica on and a specific
dietary change on blood pressure, where par cipants are assigned to groups
receiving the medica on, the dietary change, both, or neither.
4. Role of RCT in Social Science Research
A- In social science research, Randomized Controlled Trials (RCTs) are valuable
for establishing causal rela onships between interven ons and outcomes,
minimizing bias through random assignment, and providing evidence for
evidence-based prac ce and policy.
Here's a more detailed explana on of the role of RCTs in social science research:
1. Establishing Causal Rela onships:
RCTs are considered a "gold standard" for determining if an interven on
causes a specific outcome.
By randomly assigning par cipants to either a treatment or control group,
RCTs help control for confounding variables and other factors that might
otherwise influence the results.
This rigorous design allows researchers to draw stronger conclusions
about cause-and-effect rela onships.
2. Minimizing Bias:
Randomiza on helps ensure that the groups being compared are similar
at the start of the study, reducing the risk of bias.
Blinding (where par cipants and researchers are unaware of who is in
which group) further minimizes bias by preven ng expecta ons from
influencing the results.
RCTs are o en used to evaluate the effec veness of new programs or
interven ons in areas such as educa on, public health, and social welfare.
3. Evidence for Evidence-Based Prac ce and Policy:
RCTs provide strong evidence that can inform evidence-based prac ce and
policy decisions.
By demonstra ng what interven ons work and why, RCTs help ensure that
resources are allocated effec vely and that interven ons are based on
solid evidence.
However, it's important to note that RCTs are not always the most
appropriate method for every research ques on, and should be used in
conjunc on with other research methods.
4. Limita ons of RCTs:
RCTs can be expensive and me-consuming to conduct.
They may not always be feasible or ethical to conduct in certain contexts.
The results of RCTs may not always generalize to other popula ons or
se ngs.
RCTs can be cri cized for being too focused on iden fying "what works"
rather than "why things work".
5. Cri cism of use of RCT in social science research
A- Experimental design is preferred over observa onal design due to its be er
control over variables and ability to establish cause-effect hypotheses. It can be
divided into pre experimental , quasi-experimental, and true experimental
designs, with true experimental design delivering higher quality evidence due to
high internal validity and randomiza on. However, RCTs have limita ons such as
complexity, cost, ethical issues, me consump on, and difficulty in rare disease
or condi on applica on.
Conclusion
In nutshell, cri cal analysis of RCT is all about balancing the strong and weak
points of trial based on analysing main domains such as right ques on, right
popula on, right study design, right data, and right interpreta on. It is also
important to note that these demarca ons are immensely simplified, and they
are interconnected by many paths.
