Research Study Designs Flashcards
framework, or the set of methods and procedures
used to collect and analyze data on variables
research study design
type of study design used to answer a
particular research question is determined by the?
nature of the question
the goal of research
the availability of resources
the design of a study can affect the _____ of
its results
validity
case reports
case series
cross-sectional studies
descriptive
observational and experimental
analytical
cross-sectional studies
cohort studies
case-control studies
observational
researcher is documenting a
naturally occurring relationship between the
exposure and the outcome
researcher does not do any active intervention
in any individual, and the exposure has already
been decided naturally or by some other factor
observational studies
looking at the incidence of lung cancer in smokers versus nonsmokers, or
comparing the antenatal dietary habits of mothers
with normal and low-birth babies
observational
experiments where the researcher actively
performs an intervention in some or all members of
a group of participants
interventional studies
T or F: intervention could take many forms
T
administration of a drug or vaccine, performance of a diagnostic or therapeutic
procedure, and introduction of an educational tool
interventional studies
➔ Merely try to describe the data on one or more
characteristics of a group of individuals.
➔ Do not try to answer questions or establish
relationships between variables
descriptive studies / nonanalytical studies
Type of Study Design: A survey of dietary habits among
pregnant women or a case series of patients with
an unusual reaction to a drug.
Descriptive
refers to the description of a patient with an unusual disease or with simultaneous
occurrence of more than one condition
Case reports
refers to the description of a patient with an unusual disease or with simultaneous
occurrence of more than one condition EXCEPT that it is an
aggregation of multiple (often only a few) similar
cases
case series
are anecdotal and of limited value
case reports and case series
➔ Involve the collection of information on the
presence or level of one or more variables of
interest (health-related characteristic), whether
exposure (e.g., a risk factor) or outcome (e.g., a
disease) as they exist in a defined population at
one particular time.
cross-sectional studies
in ________, the
investigator also assesses the relationship between
the presence of an exposure and that of an
outcome
cross-sectional
can be thought of as
providing a “snapshot” of the frequency and
characteristics of a disease in a population at a
particular point in time
are very good for measuring the prevalence
of a disease or of a risk factor in a population
are very helpful in assessing the disease burden and healthcare needs
are usually simple to do
and inexpensive
do not pose much of a challenge from an
ethics viewpoint
cross-sectional studies
carry a risk of bias
cross-sectional
The results of the cross-sectional study may not represent the true situation in the population.
This could arise from either ____ bias or
____ bias
selection, measurement
looking for association between an
exposure and an outcome across populations
rather than in individuals.
ecological (correlational) study design
convenient to do since the data have often
already been collected and are available from a
reliable source
useful when the differences in exposure between individuals within a group are much smaller than the differences in exposure between groups.
ecological
➔ Attempt to test a hypothesis and establish causal relationships between variables.
➔ In these studies, the researcher assesses the effect of an exposure (or intervention) on an outcome.
➔ Can be observational (if the exposure is naturally
determined) or interventional (if the researcher
actively administers the intervention).
Analytical studies
defined as a “group of people with a shared characteristic
cohort
different groups of people with varying levels of exposure are followed over time to evaluate the occurrence of an outcome
cohort
➔ These participants have to be free of the outcome
at baseline
➔ The presence or absence of the risk factor
(exposure) in each subject is recorded.
➔ The subjects are then followed up over time
(longitudinally) to determine the occurrence of the
outcome.
cohort
are FORWARD-DIRECTION studies
(moving from exposure to outcome) and are
typically PROSPECTIVE studies (the outcome has not
occurred at the start of the study)
cohort studies
researcher first enrolls cases (participants with
the outcome) and controls (participants without the
outcome) and then tries to elicit a history of
exposure in each group.
case-control
these are BACKWARD-DIRECTION studies
(looking from outcome to exposure) and are always
RETROSPECTIVE (the outcome must have occurred
when the study starts)
case-control studies
cases are identified from hospital records,
death certificates or disease registries
case-control
T or F : The controls are not required to resemble cases in all respects,
except for the absence of disease.
F
What are the types of Interventional Studies?
- Randomized controlled trials
- Nonrandomized controlled clinical trials
- Interventional studies without concurrent
controls - Before-after (pre-post) studies
- Factorial study design
- Crossover study design
- Cluster randomized trials
group of participants fulfilling certain inclusion and exclusion criteria is “randomly”
assigned to two separate groups, each receiving a
different intervention
randomized controlled trials
T or F: Random assignment implies that each participant
has an equal chance of being allocated to the two
groups.
T
The use of randomization is a major distinguishing
feature and strength of this study design.
RCT
this term refers to the presence of a
concurrent control or comparator group
controlled
RCT have two or more groups :
the ___ and ___
treatment and control
receives no intervention or
another intervention that resembles the test
intervention in some ways but lacks its activity
(e.g., placebo or sham procedure, referred to
also as “placebo-controlled” or
“sham-controlled” trials) or another active
treatment (e.g., the current standard of care)
control group
In this design, participants are assigned to different
intervention arms without following a “random”
procedure.
Nonrandomized Controlled Clinical Trials
this may be based on the
investigator’s convenience or whether the participant can afford a particular drug or not
NRCT
This study design is susceptible to bias – with patients in
the two groups being potentially dissimilar – and
hence validity of the results obtained is low
NRCT
When a new intervention, e.g., a new drug,
becomes available, it is possible to a researcher to assign a group of persons to receive it and
compare the outcome in them to that in a similar
group of persons followed up in the past without
this treatment (”historical controls”)
Interventional Studies without Concurrent Control
This is liable to a high risk of bias, e.g., through
differences in the severity of disease or other
factors in the two groups or through improvement
over time in the available supportive care.
Interventional Studies without Concurrent Control
In this design, a variable of interest is measured
before and after an intervention in the same
participants
Before-After (Pre-post) studies
Type of Study Design : measurement of glycated
hemoglobin of a group of persons before and after
administration of a new drug (in a particular dose
schedule and at a particular time in relation to it) or
number of traffic accident deaths in a city before
and after implementation of a policy of mandatory
helmet use for two-wheeler drivers
Before-After studies
If two (or more) interventions are available for a
particular disease condition, the relevant question
is not only whether each drug is efficacious but also
whether a combination of the two is more
efficacious than either of them alone.
Factorial Study Design
This design allows the study of TWO INTERVENTIONS in
the SAME trial WITHOUT unduly increasing the
required number of participants, as also the study
of interaction between the two treatments.
Factorial Study Design
Type of Study Design : Two interventions – A and B. The
participants are randomly allocated to one of four
combinations of these interventions – A alone, B
alone, both A and B, and neither A nor B (control).
Factorial Study Design
The advantages of this design are:
★ Comparison of each intervention with the
control group,
★ Comparison of the two interventions with each
other, and
★ Investigation of possible interactions between
the two treatments (whether the effect of the
combination differs from the sum of effects of A
and B when given separately)
Factorial Study Design
