True experimental research designs aim to establish causal relationships. They have four key elements: manipulation of the independent variable, use of control groups, random assignment of subjects to conditions, and random selection of subjects. Randomized controlled trials are a type of true experiment that are considered the gold standard for determining cause and effect. Common true experimental designs include pre-test post-test control group designs, post-test only control group designs, and Solomon four-group designs.

1. True Experimental Research
Design
Prof. (Mr.) Asokan R
I/C of R & D, KINS, KIIT (DU), BBSR.

2. Outline
• Research design
• True experimental research design
• Elements of True experimental research design
• Randomized controlled trial (RCT).
• Phases of RCT
• Types of True experimental research design

3. Introduction

4. What is Design?

5. A design is a plan or system or for the implementation of an activity or
process, or the result of that plan or specification in the form of a prototype,
product or process.
- Wikipedia

6. What is Research design?

7. • It is a blueprint for conducting a study that maximizes control over factors
that could interfere with the validity of the findings.
• Elements control to the study design include the presence or absence of a
treatment, number of groups in the sample, number and timing of
measurements to be performed, sampling method, time frame of data
collection, planned comparisons, and control of extraneous variables.

8. Research design must contain,
(i) a clear statement of the research problem;
(ii) procedures and techniques to be used for gathering information;
(iii) The population to be studied; and
(iv) Methods to be used in processing and analyzing data.

9. One may spilt the overall research design into the following parts:
• i. The sampling design which deals with the method of selecting items to be
observed for the given study;
• ii. The observational design which relates to the conditions under which the
observations are to be made;
• iii. The statistical design which concerns with the question of how many items are
to be observed and how the information and data gathered are to be analyzed; and
• iv. The operational design, which concerns with the techniques by which the
procedures specified in the sampling, statistical and observational designs can be
carried out.

10. What is True experimental design?

11. True experimental design is a statistical approach of establishing a
cause and effect relationship between different variables. This is one of
the most accurate forms of research designs which provides a substantial
backing to support the existence of relationships.
Examples of true experimental designs are: pre-test - post-test
control group, post-test only control group, and a Solomon four group,
six-study design.

12. A true experimental design is characterized by the following
properties:
True experiments have four elements: manipulation, control , random assignment, and
random selection.
• Manipulation—the experimenter does something to at least some subjects or something
is purposefully changed by the researcher in the environment.
• Control—the experimenter introduces controls over the experimental situation,
including the use of a control group.
• Randomization—the experimenter assigns subjects to a control or experimental group
on a random basis

13. Random selection refers to how the sample is drawn from the
population as a whole, while random assignment refers to how the
participants are then assigned to either the experimental or control
groups.
It is possible to have both random selection and random
assignment in an experiment.

14. • A research study using a true experimental design is commonly called a
randomized controlled trial (RCT).
• In hospital and clinic settings, it may be referred to as a “clinical trial” and is
commonly used in drug trials.
• An RCT is considered the “gold standard” for providing information about
cause-and-effect relationships. An individual RCT generates Level II evidence
because of reduced bias provided by randomization, control, and manipulation.
• A well-controlled design using these properties provides more confidence that
the intervention will be effective and produce the same results over time.

16. Randomization
• Randomization, or random assignment, distribution of subjects to either the
experimental or the control group on a purely random basis.
• Randomization may be done individually or by groups. Several procedures are
used to randomize subjects to groups, such as a table of random numbers or
computer-generated number sequences (Suresh, 2011).
• Whatever method is used, it is important that the process be truly random, that
it be tamperproof, and that the group assignment is concealed (kept secret).

17. Why randomization?
The basic benefits of randomization include
1. Eliminates selection bias.
2. Balances arms with respect to prognostic variables (known and
unknown).
3. Forms basis for statistical tests, a basis for an assumption-free
statistical test of the equality of treatments.

18. Methods of randomization
• (1) simple - equivalent to tossing a coin for each subject that enters a trial. The
random number generator is generally used.
• (2) Block - to divide potential patients into m blocks of size 2n, randomize each block
such that n patients are allocated to A and n to B. then choose the blocks randomly.
• (3) Stratified - addresses the need to control and balance the influence of covariates.
This method can be used to achieve balance among groups in terms of subjects’
baseline characteristics (covariates).
• (4) Adaptive - changing the allocation probability according to the progress and
position of the study. It may be used to minimize the imbalance between treatment
groups as well as to change the allocation probability based on the therapeutic effect.

19. Blinding
Blinding, in research, mentions to a practice where the study
population or the stakeholders involved in research are not permitted
from knowing certain information or treatment, which may somehow
influence the study findings.
Blinding (also called masking) is typically used in randomized
controlled trials (RCTs).

21. There are basically three different types of blinding used in researches:
Single blinding or single-masked:
• In single blinding, only a single stakeholder i.e. either the participant or the investigator is not
informed of the nature of treatment the participant is receiving.
• A trial is called single-blind if only one party is blinded. Usually, the participant is
blinded and is unaware of the treatment they receive.
Double-blinding or double-masked:
• Both study population/participant and data collectors/investigators/researchers are not
aware of the kind or nature of the treatment given and who receive the treatment.
• If both ‘the participants’ and ‘the study staffs’ are blinded, it is known as a double- blind
study.

22. Triple blinding:
A clinical trial in which neither the subject nor the person governing treatment
nor an individual measuring the response to the treatment is aware of the particular
treatment received by the subject is known as triple blind. Triple blinded studies also
lengthen blinding to the data specialists.
• In triple blinding, the study participant, the data investigator or data collector and the
data analyzer- all are blinded.
Unblinded or open-label:
It is the exact opposite of blinding, where all the participant, clinicians, data
collectors, specialists are well known about the treatment/intervention they receive.

23. Control
• Control refers to the process by which the investigator holds certain conditions
constant to limit bias that could influence the dependent variable(s) / effort by the
researcher to remove the influence of any extraneous, confounding variable.
• Control is acquired by manipulating the independent variable, by randomly assigning
subjects to a group, by using a control group, and by preparing intervention and data
collection protocols to maintain consistency for all study participants.
• In experimental research, the control group receives the usual treatment or a placebo
(any treatment that has no active properties).

24. The three main types of controls are positive, negative, and procedural, and
variable controls.
A positive control group is not exposed to the experimental treatment but is
exposed to another treatment that is known to work.
A negative control a process of conducting the experiment in the exact same
way on a control group except that the independent variables are a placebo that is not
expected to produce a result.
procedural controls are designed to reduce error in conducting the
experiement.
variable control – the practice of keeping a variable constant to minimize its
influence on results.

25. Manipulation
• Manipulation is the process of “doing something,” a different dose of “something,”
or comparing different types of treatment by manipulating the independent variable
for at least some of the involved subjects.
• The independent variable might be a treatment, a teaching plan, or a medication.
• The effect of this manipulation is measured to determine the result of the
experimental treatment on the dependent variable compared with those who did
not receive the treatment.

26. Types of Experimental Designs
There are many different experimental designs (Campbell & Stanley, 1966). Each is
based on the classic design called the true experiment or RCT. The classic RCT is conducted
as follows:
• 1. The researcher recruits a sample from the population.
• 2. Baseline preintervention demographics, personal characteristics, and measurement
of the intended study concepts or dependent variables are collected from the entire
sample.
• 3. Subjects are then randomized to either the intervention or the control group.
• 4. After each group receives the experimental intervention or comparison/control
intervention (usual care or standard treatment, education, or placebo), both groups
complete postintervention measures to see if any changes have occurred in the dependent
variables.

28. Pretest-post-test control group designs,
Post-test only control group designs,
Solomon four-group design,
Factorial design ,
nested designs

30. subjects are randomly assigned to the 2 groups, both are
presented, but only the experimental group is treated. After close
observation, both groups are post-tested to measure the degree of
change in each group.

31. Randomized control group post- test only design
• Usually planned where pretest is not necessary, unavailable,
inconvenient, or likely to be reactive
• Controls internal validity factors
• E ( R )
• C ( R ) X O 1
_ O 2

32. Subjects are randomly selected and assigned to the 2 groups
(control and experimental), and only the experimental group is
treated. After close observation, both groups are post-tested, and a
conclusion is drawn from the difference between these groups.

33. Randomized Solomon Four Group Design
Pretested ( R ) O 1 X 1 O 2
Pretested ( R ) O 1 _ O 2
Un-pretested ( R ) _ X 1 O 2
Un-pretested R) _ _ O 2
Greater confidence can be placed on the findings

35. Cross-over design
• Also called as Rotation experiments / Cross-over design / Switch-over
designs
• Here four experimental treatments are applied in a restrictively
randomized manner in turn to four naturally assembled groups
• Groups X 1 X2 X3 X4
• A t 1 t 2 t 3 t 4
• B t 2 t 3 t 4 t 1
• C t 3 t 4 t 1 t 2
• D t 4 t 1 t 2 t 3

36. A crossover design is a repeated measurements design such that each
experimental unit (patient) receives different treatments during the different
time periods, i.e., the patients cross over from one treatment to another during
the course of the trial.

37. Factorial design
Factorial design involves having more than one independent
variable, or factor, in a study.
Factorial designs allow researchers to look at how multiple
factors affect a dependent variable, both independently and together.
Factorial design studies are named for the number of levels of the
factors.

39. Randomized block design
A randomized block design is an experimental design where the
experimental units are in groups called blocks. The treatments are
randomly allocated to the experimental units inside each block. When all
treatments appear at least once in each block, we have a completely
randomized block design.

40. Randomized Block Design(RBD)
Research design involves two principles
• Randomization
• Replication
• Control
Data layout
Let five treatments A, B, C, D and E replicated
for 5 times respectively then the treatment
allocation may be
Block I Block II Block III Block
IV
Block V
A E B E A
B D C A D
C A D C C
D B E B E
E C A D B