Infection preventionists often seek to make external comparisons when reviewing their hospital's healthcare-associated infection data. While previous methods involved the use of risk-stratified rates, recent methods employed by the Centers for Disease Control and Prevention include the use of a risk-adjusted summary measure called the standardized infection ratio. In utilizing the results of statistical inference, hospitals can determine if their healthcare-associated infection experience, by way of the standardized infection ratio, is different from the national baseline. Such results can help assess success of prevention efforts, as well as prioritize additional prevention activities based on both statistical and practical significance. This chapter focuses on the methods used to calculate the standardized infection ratios and how a hospital can interpret the standardized infection ratio along with statistical evidence.