The A0 performance value that the 217Plus model is to use in Bayesian equations. This value is the effective number of failures associated with the predicted failure rate. It represents the uncertainty in the failure rate estimate. The default is 0.5, which represents a large degree of uncertainty inherent when a diverse data set is used. If you have enough data to obtain an observed uncertainty, you can enter a different value. Additional information about this value appears in the Handbook of 217Plus Reliability Prediction Models, which is available from the Reliability Analysis Information Center (RIAC). For more information, see Ordering Reliability Standards.