STUDY DESIGN

STUDY DESIGN

1. Descriptive

   • Case report
     • One case of unusual findings
     • Limitations:Cases may not be generalizable and not based on systematic studies
     • Strengths: identifies new diseases ,detect new drug side effects and Identifies rare manifestations of a disease.
     • Present
     • Rare diseases
       • E.g lyme disease in individual
   • Survey
     • Estimate the frequency and distribution of o utcomes
     • Strengths:Provides some data
     • Limitations:Need to take care resampling (Sign) and design of questions
     • National Crime Victimization Survey
   • Case series
     • Multiple cases of unusual findings
     • Present
     • Strengths :hypothesis generation and established risk factors
     • Limitations:cannot study cause and effect relationships
     • Rare diseases that effect group of people
       • E.g lyme disease

2. Analytic

   • Observational Studies
     • Cohort
       • comparing individuals with a known risk factor and without it.
       • prospective/longitudinal studies
       • Strengths:Can study several outcomes for each exposure and Exposure status determined before disease detection.
       • Limitations:Expensive ,time-consuming and Inefficient for rare diseases and
       • Health Studies Nurses
         • E.g Framingham
     • Case-control
       • To determined exposure associate with outcome
       • Retrospective Study
       • Strengths: less expensive and time consuming , suitable for rare diseases and can identify more than one risk factorsin same data.
       • E.g Transplacental Carcinogensis
       • Limitation : exposure measurements taken after disease occurrence.
     • Cross-sectional
       • Prospective study
       • collect all data at a set point in time
       • Strengths : Fast , inexpensive , generate hypothesis and can involve a large sample size of study population
       • Limitations : Weak observational design
       • E.g Cancer
   • Experimental Studies (know the causes)
     • Laboratory
       • Investigator has almost complete control over experimental conditions
       • Prospective Study
     • Randomized Controlled Trials
       • prospective Study
       • To know the relationship between exposure and effect.
       • Strength:provides most convincing evidence of relationship between exposure and effect , can demonstrated causal and effect and gold strand
       • Limitations :expensive and required long-term
       • E.g Multiple Risk Factor Intervention Trial (Mrfit)