Penelitian Kuantitatif di Bidang Kesehatan

Bobby M. SyahrizalMetodologi Penelitian 2007

What is a study design?A framework for the different elements or activities the study consists ofA plan of action that structures the work that needs to be done to collect the information we need to answer our research questions

The study designs describes (often prescribes)

What we are going to do: i.e.the methods/techniques we are going to useWhen we are going to this and in what particular orderThe population that we involve in our study (study population consisting of informants (qual) or respondents (quant))

Study designs: TerminologyExperimental study = RCTCohort study = follow-up studyProspective = concurrentRetrospective = non-concurrent = historicalCase-control study = case-referent studyCross-sectional study = transversal study = surveyCase series = patient seriesEcological study = population studyGeographical correlation studyTime trend study

STUDY DESIGN & CAUSAL EVIDENCEExperimental studyRCTCohort studyProspectiveRetrospective Case-control studyCross-sectional studyCase seriesCase reportEcological studyCausal inferenceCause-effect researchAnalytical researchDescriptive researchLongitudinalTransversal Individual characteristicPopulationManipulationObservation

Overview of study designs

Cohort studyIn a cohort study a group of individuals (study group) that is exposed to a risk factor is compared with a group of individuals not exposed to that factor (control group)The researcher follows both groups over time and compares the occurrence of the problem that (s)he expects to be related to the risk factorProspective (looking into the future)

Cohort studyExposed to risk factorNot exposed to risk factorProblem presentProblem not presentProblem presentProblem not presentComparepresentfuture

Case-control studyA group of people with a problem (study group) is compared with a group of people (control group) who dont have the problemThe comparison helps to locate factors that may have contributed to the problemRetrospective (looking back)

Case-control studyCompareAssociated factordpresentAssociated factors absentAssociated factors presentAssociated factorsabsentMalnourished childrenWell-nourished childrenpresentPast

Cross-sectional studyCompares groups-with-a-problem (cross-sections) within a population with other groups (cross-sections) within that population that do not have that problemLooks at present situation

Experiment (randomised clinical trial)Manipulation of one or more independent variablesVery narrowly defined research problem that concerns the testing of a assumed causal relationship Always makes use of a control groupStudy group as well as control group are selected at randomLaboratorium-like circumstances

RCTs not often used in social sciences:Phenomena too complex; many variables play a role and interactMany variables are unique in time/placeOften ethical problemsDifficult to organize

Quasi-experimentCompares a group that has been subjected to an intervention (study group) with a group that has not been interfered with (control group)To measure the effect of the interventionprospective

Quasi-experimentStudy group beforeControl groupbeforeInterventionStudy groupafterControl group afterCompare

Before-after studyCompares the situation of a group of individuals (study group) before an intervention with the same group after the intervention

Before-after studyStudy group beforeInterventionStudy group afterCompare

Explorative and descriptive studies do not have pre-fab designs. The researcher creates his/her own work plan (which discusses how, when, whom)RCTs, cohort studies, case-control studies, cross-sectional studies, quasi-experiments, and before-after studies have pre-fab designs.