In a seroepidemiologic survey of health workers representing a spectrum of exposure to blood and patients with hepatitis B virus (HBV), it was found that infection increased as a function of contact. Table E6.19 provides data for hospital workers with uniform socioeconomic status at an urban teaching hospital in Boston, Massachusetts.

Test to compare the proportions of HBV infection between the four groups: physicians with frequent exposure, physicians with infrequent exposure, nurses with frequent exposure, and nurses with infrequent exposure. State clearly your null and alternative hypotheses and choice of test size.