Is fast food messing with your hormones? examine the results of a study1 investigating whether fast food consumption increases one’s concentration of phthalates, an ingredient in plastics which has been linked to multiple health problems including hormone disruption. the study included 8877 people who recorded all the food they ate over a 24-hour period and then provided a urine sample. two specific phthalate byproducts were measured (in ng/ml) in the urine: dehp and dinp. find a 95% confidence interval for the difference, μf-μn, in mean concentration between people who have eaten fast food in the last 24 hours and those who haven’t. the mean concentration of dehp in the 3095 participants who had eaten fast food was x¯f=83.6 with sf=194.7 while the mean for the 5782 participants who had not eaten fast food was x¯n=59.1 with sn=152.1.the 99% confidence interval is to .