Iln the table below, there are examples of unstratified as well as stratum-specific estimates of odd ratios from four different epidemiologic studies of different exposures and outcomes, all stratified by smoking status. Please indicate for each study if confounding is present or absent. Study OR OR OR Confounding (crude) (smokers) (non-smokers) present or Absent? _ _ _ 4 .48 .46 .50