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Research Design & Methodology
Presentation Outline:
Definition
Elements of research
methods
Pyramid of research design
How to assess research
designs for Validity & Error
The 4 basic clinical
research designs and
examples
Research Methodology: Definition
a collective term for the structured process of conducting
research
there are many different methodologies used in various
types of research
the term is usually considered to include research design,
data gathering and data analysis
The research methods are the most important part of any
study.
This is the blueprint for your study of which everything is
built upon.
Research Methods Research methods consist of:
Study design
• (e.g., randomized controlled trial, cohort, case-control)
Population to be sampled
• Sample size and power calculation
• Inclusion and exclusion criteria
• Subject selection and assignment
‒ Assignment to either the control group or the treatment group
Treatment
Procedures
Measurements
Data analysis
Importance of the Research Question
Research design and methods will be driven by
the research question
Based on this question, is it necessary to select a
research design that is both ethical and feasible
For example:
Does cigarette smoking cause lung cancer?
• Hypothesis: Cigarette smoking causes lung cancer.
Does circumcision cause penile cancer?
• Hypothesis: Circumcision causes penile cancer.
Importance of Validity and Error When selecting a research design there are two elements
you must consider:
Validity
the extent to which a test measures what it claims to measure
• it is vital for a test to be valid in order for the results to be
accurately applied and interpreted
is determined by a body of research that demonstrates the
relationship between the test and whatever it is intended to measure
Reliability
the degree to which an assessment tool produces stable and
consistent results
Error
represents something other than what is being measured
Types of Validity Internal Validity
the ability of a study to unambiguously determine the causal relationship
between two or more variables: with what certainty can we conclude that X
caused the measurable difference we found in Y?
External Validity (often called generalizability)
the degree to which conclusions can be generalized to the universe outside of
the study (can the results of the study be generalized to the sample population
or other groups?)
It is through proper study design that high levels of validity, both internal
and external, can be achieved
Without internal validity, you cannot have external validity
Types of Validity: Examples Internal Validity
a study may have poor internal validity if testing was not
performed the same way in treatment and control groups
or if confounding variables were not accounted for in the
study design or analysis
External Validity
a study performed exclusively in a particular gender,
racial, or geographic sub-group, such as white females
in Appalachia, may not be applicable to Hispanic men in
the northwest
Types of Error
Random Error – a wrong result due to chance
vary in magnitude and direction
Systematic Error – a wrong result due to bias
tend to be consistent in magnitude and/or direction
Validity vs. Error Error directly affects the validity of a study
High Error results in Low Validity
Err
or
Valid
ity
Low Error results in High Validity
E
rro
r
Valid
ity
• one of the simplest and most powerful tools in research; quantitative, comparative,
controlled experiments where subjects are allocated at random to receive one of
several clinical interventions one of which is the standard of comparison or control
• observe the effect on a specific group with a certain trait over time
• individuals with differing exposures to a suspected factor are identified and
then observed for the occurrence of certain health effects over a period of time
(ex. does exposure to smoking cause lung cancer)
• Retrospectively compares patients with a disease to those who do not have
the disease and how frequently the exposure to a risk factor is present in each
group to determine the relationship between the risk factor and the disease
• participants are not assigned by chance to different treatment groups and may
choose which group they want to be in, or they may be assigned to the groups by
the researchers
• measures the prevalence of health outcomes in a population at a point in
time (single point of data collection) or over a short period of time
• disease and exposure measured simultaneously in a given population
(ex. looking at prevalence of breast cancer in a population)
• an in-depth study of one person’s every aspect of life and history to seek
patterns and causes for disease
• can be retrospective or prospective
• lowest level of evidence and first line of evidence where new issues and ideas emerge
• unique and cannot be explained by known diseases or syndromes that show an important
variation of the disease or condition
• show unexpected events that may yield new or useful information
The Pyramid of Research Design
The 4 Basic Clinical Research Designs
Clinical Trials, Cohort (longitudinal), Case-Control, Case
Series
The 4 designs fall under two categories: experimental and
observational
Experimental (always contains an intervention)
1. Clinical Trial - Randomized, Controlled, Double-Blind
1a. Quasi-experimental – lacks randomization and blinding
Observational (does not contain an intervention)
2. Cohort or Longitudinal
3. Case-Control
4. Case Series
R
Direction of Inquiry
Randomized Controlled Trial (RCT)
Heart Attack
Yes No
Shovel Snow a b
Did not shovel snow c d
Key features of a RCT Gold standard for determining the effect of clinical intervention in a
group of patients
Random allocation of subjects to intervention groups
Patients, providers and investigators unaware of the treatment given
to the groups (i.e., single/double/triple blinded)
Subjects are aware of being observed and may behave differently
regardless of the actual effect induced by the treatment intervention
(Hawthorne effect)
Patients are analyzed according to the initial treatment assignment
irrespective of whether they received the intended intervention
(intention to treat analysis)
Analysis is focused on estimating the size of difference in the
predefined outcomes between intervention groups
Cohort (longitudinal)
?
Direction of Inquiry
Heart Attack
Yes No
Shovel Snow a b
Did not shovel snow c d
Key Features of a Cohort Study Cohort of individuals divided into two or more groups based on presence
of risk factor/individual characteristic.
Individuals are followed for a period of time.
Frequency of development of disease or a desired outcome is compared
between the two groups.
Computation of RR (Relative risk), AR (Absolute risk), & Incidence
RR: the probability that a member of an exposed group will develop a
disease relative to the probability that a member of an unexposed group will
develop that same disease
AR: the ratio of the number of people who have a medical event divided by all
of the people who could have the event because of their medical condition
Incidence rate computed for both the exposed and unexposed groups.
RR of mortality was computed by comparing mortality rates in
vaccinated and unvaccinated individuals followed during 3 influenza
seasons.
Example
Case-control
Direction of Inquiry
Heart Attack
Yes No
Shovel Snow a b
Did not shovel snow c d
Key features of Case-Control Type of a retrospective study.
Begins with identification of cases (individuals with
diagnosis of a condition), and controls (individuals without
condition).
Clinical course of the patients followed through medical
charts and other databases.
The degree of association between the suspected risk factor
and outcome (disease) ascertained by OR (odds ratio).
OR: Equivalent of RR used to estimate likelihood of an association.
Presented study identified patients with CKD and followed them retrospectively
through medical charts. It found renal function declined faster in patients with
higher phosphate levels at baseline
Example
Heart Attack
Yes No
Shovel Snow a b
Did not shovel snow c d
Case Series
?
Present Time
Types of Retrospective Studies Case report: Report of one unusual case.
Case series: Report of multiple similar unusual or
instructive cases.
Case-control: Estimates effect of exposure on outcome.
Cases and controls established on presence of a
condition/outcome.
Cohort or Historic Cohort: Used to identify exposure and
outcome information retrospectively. Considered to be the
best approach to identify incidence and natural history of
disease.
Strength Method Error Validity
Strongest RCT
Cohort
Case-Control
Weakest Case Series
Research Design Matrix
References New York University
http://www.nyu.edu/classes/bkg/methods/005847ch1.pdf
Science Blurtit
http://science.blurtit.com/23704/what-is-research-methodology-
University of Minnesota Bio-medical Library
http://hsl.lib.umn.edu/biomed/help/understanding-research-study-
designs
About.com - Psychology
http://psychology.about.com/od/researchmethods/f/validity.htm
Healthcare Value Analysis Magazine
http://valueanalysismag.com/good-evidence-the-missing-link/
Baltimore County Public Schools
http://www.bcps.org/offices/lis/researchcourse/develop_writing_method_
qualitative.html
Previous internal Advocate research department presentations
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