<prompt> Incidence rate can be calculated from:Coho studyCase control studyCross sectional studyDescriptive study  <response>: Only Coho study follows patient for a definite time period. It proceeds from cause to effect. So incidence can be calculated. Besides relative risk as well as attributable risk are also derived from coho study. While case control study study yields only estimate of relative risk. Cross sectional study yields prevalence rate. Ref: Park 21st edition, page 71. 