Description: Recognizing an opportunity to help serve its members in this age of increased financial oversight, the Health Section of the Society of Actuaries commissioned a series of guides on the use of statistical techniques specifically geared for the work of health actuaries. In this first guide in the series, the topic is an estimate well-known to health actuaries- the calculation of incurred but not reported [IBNR] health claims reserves. In particular, this guide focuses on the development of confidence intervals around IBNR estimates.