This document provides an overview of randomized controlled trials (RCTs). It discusses that RCTs are used to test interventions by randomly assigning participants to either an intervention or control group. The two groups are then compared on outcomes to see if any differences were caused by the intervention. It outlines the basic steps in RCTs, including developing a protocol, randomization methods, intervention/manipulation, follow-up, and outcome assessment. It also discusses types of RCT designs such as parallel group trials and crossover trials, as well as concepts like blinding and stratification.

1. RANDOMIZED CONTROL TRAIL
RCT
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Prof.Dr.Chinna Chadayan.N
RN.RM., B.Sc (N)., M.Sc (N)., Ph.D
(N).,
Professor,
Enam Nursing College – Savar,
Bangladesh
1 yr M.Sc(N)
Unit – 8b

2. INTRODUCTION
• Randomization as a basic principle of experimental design in
the 1920s was developed by RA fisher who presented
randomization as an essential ingredient of his approach to
the design and analysis of experiments, validating
significance tests predominantly in agricultural research
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3. RCT
RANDOMIZED CONTROLLED TRIAL
An RCT is conducted to test whether an intervention or treatment
works.
The investigators will randomly allocate the participants either to
the intervention group (which will receive the therapy or preventive
action), or to control group (which will receive the usual or no
treatment).
The two groups are then compared on outcome of interest. Since
random assignment equalizes the groups on all other variables,
any differences in outcome between treatment and control were
actually caused by the treatment.
Study
sample
Interventio
n group
Control
group
Outcome
Outcome
Randomizatio
n
Follow up Analysis

4. BASIC STEPS IN RANDOMIZED
CONTROLLED TRIALS
1. Drawing up a protocol
2. Selecting reference and experimental populations
3. Randomization
4. Manipulation and intervention
5. Follow up
6. Assessment of outcome
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5. 1.THE PROTOCOL
• Study is conducted under strict protocol
• Specifies aims and objectives of study; questions to be
answered; criteria for selection of study and control groups;
parties involved in trial; stage of evaluation of study
• Aims at preventing bias and to reduce sources of error in
study at times preliminary tests ie pilot studies are done –
to find feasibility of certain procedures or acceptability of
certain policies
• Should be agreed by all concerned before trial begins
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6. 2. SELECTING REFERENCE AND
EXPERIMENTAL POPULATIONS
• Reference/ target population:
• Population to which findings of trial; if found successful, are expected to be
applicable
• Can be as broad as a mankind or geographically limited or limited to persons
in specific age, sex, occupational or social group
• Experimental population:
• Derived from reference population - randomly
• Population that participates in the study
• They should have same characteristics as reference group
• They should be informed, should be qualified and eligible
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7. 3.RANDOMIZATION
• Randomization procedure by which participants are
allocated into groups called study and control
groups
• Attempt to eliminate bias and allow comparability
• Selection bias
• Every individual gets an equal chance of being
allocated into any of trial group
• Done only after participant has entered the study i.e,
given consent and is qualified
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8. CRITERIA FOR RANDOMIZATION
• Unpredictability
• Each participant has the same chance of receiving any of the
interventions.
• Allocation is carried out using a chance mechanism so that
neither the participant nor the investigator will know in advance
which will be assigned.
• Balance
• Treatment groups are of a similar size & constitution, groups are
alike in all important aspects and only differ in the intervention
each group receives
• Simplicity
• Easy for investigator/staff to implement
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9. METHODS OF
RANDOMIZATION
THE COMMON TYPES OF RANDOMIZATION
INCLUDE
1.SIMPLE
2.BLOCK
3.STRATIFIED AND
4.UNEQUAL RANDOMIZATION
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10. 1.Simple randomization
Randomization based on a single sequence of random
assignments is known as simple randomization .
The most common and basic method of simple
randomization is flipping a coin
Advantage
Simple and easy to implement
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11. 2.Stratified randomization
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Stratification prior to randomization can be used to ensure that
the number of patients assigned to the experimental and control
arms are balanced with respect to important attributes
(stratification variables).
Examples of stratification variables are gender or disease stage.
The purposes of stratification are two-fold.

12. 3.Block randomization
 the block randomization method is designed to randomize subjects into groups that
result in equal sample sizes.
 This method is used to ensure a balance in sample size across groups over time.
 Blocks are small and balanced with predetermined group assignments, which keeps the
numbers of subjects in each group similar at all times.
 The block size is determined by the researcher and should be a multiple of the number
of groups (i.E., With two treatment groups, block size of either 4, 6, or 8).
 Blocks are best used in smaller increments as researchers can more easily control
balance
Advantage
balance between the numbers of participants in each group is guaranteed during course
of randomization.
If the trial is terminated before enrolment is completed, balance will exist in terms of
number of participants randomized to each group.
Disadvantage
analysis of data is more complicated than simple randomization. Also with fixed blocks,
people involved in the trial may be able to predict the group assignment of participants
being randomized at the last in the block. Block randomization
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14. 4.Unequal randomization
 When two or more treatments under evaluation have
a cost difference it may be more economically
to randomize fewer patients to the expensive
treatment and more to the cheaper one.
The substantial cost savings can be achieved by
adopting a smaller randomization ratio such as a
of 2:1, with only a modest loss in statistical power.
When one arm of the treatment saves lives and the
other such as placebo/medical care only does not
much to save them in the oncology trials. The subject
survival time depends on which treatment they
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15. 4. MANIPULATION &
5.INTERVENTION
• Manipulation
• This is to manipulate the study
• Done by application or withdrawal or reduction of
suspected causal factor
• Creates independent variable – whose effect is then
determined by measurement of final outcome ie
dependent variable
• FOLLOW-UP:
• Examination of experimental and control groups at defined
intervals of time
• Attrition may be seen
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16. 6.ASSESSMENTOF
OUTCOME
ASSESSMENT: of outcome of trials
• Positive results: benefits of experimental measures
• Negative results: severity and frequency of side effects
and complications of any
 Incidence of negative and positive results is compared
in both the groups – and differences if any are tested
statistically.
Bias may arise from error of assessment of outcome:
 subject variation
 observer bias
 bias in evaluation
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17. BLINDING
• SINGLE BLIND TRIALS:
• PARTICIPANT IS NOT AWARE WHETHER HE BELONGS
TO STUDY OR CONTROL GROUP
• DOUBLE BLIND TRIALS:
• NEITHER THE PARTICIPANT NOR THE DOCTOR IS
AWARE OF GROUP ALLOCATION OR THE TREATMENT
BEING RECEIVED
• TRIPLE BLIND TRIALS:
• PARTICIPANT, DOCTOR AND INVESTIGATOR ALL THREE
ARE BLIND
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18. TYPES OF RCT DESIGN
1. PARALLEL GROUP TRIAL DESIGN
2. CROSS-OVER TRIAL DESIGN
3. FACTORIAL DESIGN
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19. • 1. A PARALLEL Study is a type of clinical study where
treatment and controls are allocated to different
individuals.
• In this two groups of treatments, a and b, are
so that one group receives only a while another
group receives only b
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20. • 2. CROSS-OVER TRIAL DESIGN
• In these types of studies each patient serves as his own control.
Each patient gets both treatments.
• Each patient receive first treatment then washout time is
provided then other treatment is provided to the same
• This ‘carry-over effect’ or the ‘spill-over effect’ of the first intervention
could result in error in the reading of the second intervention. Hence
enough time is allowed to pass, known as ‘wash-out period’ between
the two interventions.
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21. • 3.FACTORIAL DESIGN
• Studies involving two or more factors while randomizing are
called factorial.
• Factorial design permits researchers to investigate the joint
effect of two or more factors on a dependent variable.
• Used when it is desired to study the influence of a number
factors on the treatments compared as well as their
interaction with different treatments factors on a dependent
variables l design
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24. THANK YOU
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