4 Middle Ear Effusion in BreastFed and BottleFed Infants A common symptom of otitus media in young children in the prolonged presence of fluid in the middle ear, known a middle-ear effusion. The presence of fluid may result in termporary hearing loss and interfere with normal learning skills in the first two years of life. One hypothesis is that babies who are breast-fed for at least 1 month build up some immtmity against the effects of the disease and have less prolonged effusion than do bottle-fed babies. A small study of 24 pairs of babies is setup, where the babies are matched on a one-to-one basis according to age, sex, socioeconomic status, and type of medications taken. One member of the matched pair is a breast-fed baby, and other member is a bottle fed baby. The outcome variable is the duration of middle-ear effusion after the first episode of otitus media. The results are shown below. Pair Duration of effusion in Duration of effusion Difference Number breast-fed bab in bottle-fed bab d : 2 11 35 3 7 4 24 182 7 6 E- 28 33 58 223