36 Cortisol is a hormone that plays an important role in mediating stress There is growing awareness that expo sure of outdoor workers to pollutants may impact cortisol levels The article Plasma Cortisol Concentration and Lifestyle in a Population of Outdoor Workers Ind J of Envir Health Res 2011 62 71 reported on a study involving three groups of police officers 1 traffic police TP 2 drivers D and 3 other duties O Here is summary data on cortisol concentration ng ml for a subset of the officers who neither drank nor smoked Group Sample Size 0 36 50 Mean 174 7 160 2 153 5 61 SD 50 9 37 2 Assuming that the standard assumptions for one way ANOVA are satisfied carry out a test at significance level 05 to decide whether true average cortisol concen tration is different for the three groups Note The inves tigators used more sophisticated statistical methodology multiple regression to assess the impact of age length of employment and drinking and smoking status on cortisol concentration taking these factors into account concentration appeared to be signifiantly higher in the TP group than in the other two groups