Chi‐Square Contingency Tables

Methicillin - resistant Staphlococcus aureus (MRSA) is a significant cause of infection as a result of treatment in a hospital as well as community morbidity and mortality. The data comprise the frequencies of hospital - acquired and community - acquired MRSA antibiotic sensitivities, which exhibit resistance to five or more antibiotics and to less than five antibiotics. The data are tabulated in the form of a 2 X 2 contingency table and are presented in this chapter. When the data are counts or the frequencies of particular events and can be expressed as a contingency table, then they can be analyzed using the x2 distribution. When applied to a 2 X2 table, the test is approximate and care needs to be taken in analyzing data when the expected frequencies are small, either by applying Yate 's correction or by using Fisher ' s 2X2 exact test.