Research is the process of answering a question that can be answered by appropriate collected data
Research Question is an interrogative statement that focuses on what variable or concepts are to be described and what relationships might exist between variables
Research Question is also ;
a quantity to estimate
a characteristic to describe or compare
a relationship to establish
Research Question : What is (or was) the frequency of a disease in a certain place at a certain time?
the answer to this question would be descriptive
to answer a question correctly, the data must be obtained and described appropriately
The rules that governs the process of collecting and arranging the data for analysis are called researchdesigns
Some research designs are appropriate for hypothesis generation and some are appropriate for hypothesistesting.Some designs can be used for either, depending on the circumstances.
Research Question : What cause the disease (outcome)?
Hypothesis Generation - is the process of developing a list of possible candidates for the causes of the disease and obtaining initial evidence that supportsone or more of these candidates
Hypothesis Testing - is done when one or more hypotheses are generated and then tested by making predictions from the hypotheses and examining new data to determine if the predictions are correct
The basicfunction of mostepidemiologicresearchdesigns is either to ;
describe the pattern of health and problems accurately or
to enable a fair, unbiasedcomparison to be made beween a group with and a group without a risk factor, a disease, or a preventive or therapeutic intervention
A good epidemiologic research design should perform the following functions ;
enable a comparison of a variable (e.g. disease frequency) between two or more groups at one point in time or, in some cases, within one group before and after receiving an intervention or being exposed to a risk factor
allow the comparison to be quantified in absolute terms (as with a risk difference or rate difference) or in relative terms (as with a relative risk or odds ratio)
A good epidemiologic research design should perform the following functions ;
permit the investigators to determine when the risk factor and the disease occured, to determine the temporalsequence
minimizes biases, confounding, and other problems that would complicate interpretation of the data
Types of Research Design
some research questions can be answered by more than one type of research design, the choice of design depends on a variety of considerations, including the clinicaltopic (e.g. whether the disease or conditions is rare or common) and the cost and availability of data
research designs are often described as either observational or experimental
each type of research design has advantages and disadvantages
Qualitative Research Advantages
generates hypotheses and initial exploration of issues in participants’ own languagewithoutbias of investigator
Qualitative Research Disadvantages
cannot test study hypotheses
can explore only what is presented or stated
has potential for bias
Cross - Sectional Surveys Advantages
are fairly quick and easy to perform
are useful for hypothesis generation
Cross - Sectional Surveys Disadvantages
donot offer evidence of a temporalrelationship between risk factors and disease
are subject to late-looking bias
are notgood for hypothesis testing
Ecologic Studies Advantages
fairlyquick and easy to perform
useful for hypothesis generation
Ecologic Studies Disadvantages
donot allow for causal conclusions to be drawn because the data are not associated with individual persons
are subject to ecologicfallacy
are not good for hypothesis testing
Cohort Studies Advantages
can be performed retrospectively or prospectively
can be used to obtain a true (absolute) measure of risk
can study many disease outcomes
are good for studying rare risk factors
Cohort Studies Disadvantages
are time consuming and costly (especially prospective studies)
can study only the risk factors measured at the beggining
can be used only for common diseases
may have losses to follow up
Case - Control Studies Advantages
fairly quick and easy to perform
can study many risk factors
good for studying rare diseases
Case - Control Studies Disadvantages
can study many risk factors
good for studying rare diseases
canobtainonly a relative measure of risk
subject to recall bias
selection of controls may be difficult
temporal relationships may be unclear
can study only one disease outcome at a time
RandomizedControlled Trials Advantages
gold standard for evaluating treatment interventions (clinical trials) or preventive interventions (field trials)
allow investigator to have extensive control over
timeconsuming and usually costly
can study onlyinterventions or exposures that are controlled by investigator
may have problems related to research process
RandomizedControlled Trials Disadvantages
timeconsuming and usually costly
can study only interventions or exposures that are controlled by investigator
may have problems related to therapy changes and dropouts
may be limited in generalizability
often unethical to perform at all
SystematicReviews and Metaanalysis Advantages
decrease subjective element of literature review increase statistical power
allowexploration of subgroups
providequantitative estimates of effect
Systematic Reviews and Metaanalysis Disadvantages
mixing poor quality studies together in a review or meta-analysisdoesnot improve the underlying quality of studies
Costeffectiveness Analysis Advantage
clinically important
Costeffectiveness Analysis Disadvantage
difficult to identify costs and payments in many health care systems
Observational Studies
investigators observe groups of study participants to learn about the possible effects of a treatment or risk factor
assignment of participants to a treatment group or a control group remains outside the investigators control
can be either descriptive or analytic
Experimental Studies
the investigators has merecontrol over the assignment of participants, often placing them in treatment and control groups (e.g. randomization method before the start of any treatment)
Descriptive
distribution of health-related states
describes disease occurence as to person, place,time
studies generate hypothesis
no hypothesis are specified in advance
preexisting data are often used
associationsmay or maynot be causal
Analytic
determinants of health related states, it examines association between variables
studies testhypothesis
hypothesis are specified in advance
new data are often collected
differences between groups are measured
Qualitative Studies
involves an investigation of clinical issues by using anthropologic techniques such as ethnographicobservation,open- ended semistructured interviews, focus groups, and key informant interviews
investigators attempt to listen to the participants without introducing their own bias as they gather data
results are reviewed and patterns in the data are identified in a structured and sometimes quantitative form
Qualitative Studies
results from qualitative research are often invaluable for informing and making a sense of quantitative results and providing greater insights into clinical questions and publichealth problems
the two approaches quantitative and qualitative are complementary with qualitative research providing rich,narrative information that tells a story beyond what reductioniststatistics alone might reveal
Cross - Sectional Surveys
aka prevalencesurvey, a survey of population at a single point in time or over a veryshort period of time
may be performed by trained interviewers in ;
people’shomes
by telephoneinterviewers
by mailed,emailed
web-based questionnaires
Cross - Sectional Surveys
useful for determining the prevalence of risk factors and the frequency of prevalent cases of certain diseases for a defined population (estimate the burden of disease)
useful for measuring current health status and planning for some health services including setting priorities for disease control (establish baseline data), many surveys have been undertaken to determine the knowledge, attitudes, and health practices or various populations, with the resulting data increasingly being made available to the general public
Cross - Sectional Surveys Disadvantages
data on the exposure to risk factors and the presence or absence of disease are collected simultaneously, creating difficulties in determining the temporalrelationship of a presumed cause and effect
e.g. difficult to establish the causality (chicken or the egg dilemma)
Cross - Sectional Surveys Disadvantages
biased in favor of longer lasting and more indolent (mild) cases of diseases
more likely to be found via - survey because people live longer with mild cases, enabling larger numbers of affected people to survive and be interviewed.Severe diseases that tend to be rapidly fatal are lesslikely to be found
neyman bias or late-look bias - it is known as length bias in screening programs, which tend to find (and select for) less agressive illnesses because patients are morelikely to be found by screening
health - participant bias
Cross - Sectional Surveys Disadvantages
repeatedcross - sectional surveys - may be used to determine changes in risk factors and disease frequency in population over time (but not the nature of the association between risk factors and diseases)
example - participants who reported immunization against a disease had fewer cases of the disease
consider if this finding actually meant that people who sought immunization were more concerned about their health and less likely to expose themselves to the disease, known as health-participant bias