Any time a healthcare facility considers investing in a new intervention - a medicine, a device, a piece of equipment, and even a training program - one of the first considerations will be . The facility has a responsibility, both financial and ethical, to weigh the cost of an investment with the likelihood and extent of patient benefits. We would all love to live in a world where hospitals could invest in any and all interventions without thought as to cost and return on investment. Instead, we face a reality in which not only are financial resources limited, but also personnel, space, and even time are constrained. As a result, when millions of dollars and patients' lives are at stake, calculating cost effectiveness of an intervention has a lot on the line.