Group of smokers followed up for 10 years to find incidence of cancer lung. What type of study is this?

B i.e. Prospective cohort studyRef: Park, 24th edition, page 80; Leon Gordis, Epidemiology, 5th editionExplanation:Cohort study is otherwise called as incidence study. Cross sectional study is otherwise called as prevalence study.Comparison of case control and cohort studiesS.No.FeaturesCase control studiesCohort studies1Study groupPersons with disease (outcome)Exposed persons (risk factor)2Comparison groupPersons without disease (controls)Non exposed persons3Measurements of riskOdds ratioRelative risk, attributable risk, Population attributable risk4Natural history of diseaseHard to establishEasily establish5Time of studyShortLong6CostInexpensiveExpensive7Sample size neededSmallLarge8Best whenDisease is rareExposure is rare9BiasSelection bias (occur during selection of cases and controls)Hawthorne bias