<prompt> Which of the following is true about Cohort study?Incidence can be calculatedIt is from effect to causeIt is inexpensiveShorter time than case control  <response>: Ans: A Incidence can be calculated Ref: Text book of preventive and social medicine, K Park, 22nd edition. page no 72Explanation:Cohort studyIt is an important study design to measure incidence.It is followed from exposure to outcome cause to effect, unlike ease control study effect to causeIt involves follow up of a cohort group with common character, birth cohort, cohort joining service in particular year etc.During follow up exposure and outcome is measured at periodic intervals OutcomeContinuousDiscreteNumericalOrdinalDichotomousPolvchOtomousXominalPolychotomousOrdinalContinuousPearson Correlation RegressionPearson Correlation RegressionSpearmanRankcorrelationt testANOVAANOVADiscrete- do -- d -- do -- do -- do -- do -NumericalOrdinalSpearmanRankcorrelationSpearmanRankcorrelationSpearmanRankcorrelationMann Whitney U testKruskal Wallis testKruskal Wallis testDichotomoust testt testMann Whitney U testChi square for 2x2 tableChi square for r x c tableChi square for linear trend in proportionsPolychotomousOrdinalANOVAANOVAKruskal WallisChi square for r x c tableChi square for r x c tableChi square for r x c tablePolychotomousOrdinalANOVAANOVAKruskal WallisChi square for linear trend in proportions- do -- do -Generally followed for long time, until outcome occursThus, it involves high costMeasures relative risk, attributable risk, population attributable risk as strength of association 