Question: A common symptom of otitis media in young children is the prolonged presence of fluid in the middle ear, known as middle-ear effusion. The presence of fluid may result in temporary hearing loss and interfere with normal learning skills in the first 2 years of life. One hypothesis is that babies who are breast fed for at least one month build up immunity against the effects of the disease and have less prolonged effusion than formula fed babies. A small study of 24 pairs of babies is set up, where babies are matched on a one-to one basis according to age, sex, socio-economic status, length of gestation, and medications used. One member of each matched pair is a breast-fed baby whereas the other member is a formula fed baby. The outcome variable is the duration of middle ear effusion after the first episode of otitis media.

a) If the data is assumed to be normally distributed, what is the appropriate test? Perform that test using a =. 05.

b) If the data are assumed not to be normally distributed, one appropriate nonparametric test that can be applied is the sign test. Perform this test using a =. 05.

c) Which of these tests do you believe to be the most appropriate for the data? Justify your answer.