Inverse measure

An inverse measure is a measure in which a lower performance rate is better. Therefore, a zero performance rate for these measures is a good score. For example, the National Healthcare Safety Network calculates most healthcare-associated infections (HAIs) as a standardized infection ratio (SIR). The SIR compares the actual number of HAIs (the numerator) with the predicted number based on the baseline U.S. experience (e.g., standard population), adjusting for several risk factors found to be most associated with differences in infection rates. The goal is to have the numerator equal to or very close to zero, thereby having an SIR equal to or very close to zero.