A new model with bathtub-shaped failure rate using an additive Burr XII distribution

It is a common situation that the failure rate function has a bathtub shape for many mechanical and electronic components. A simple model based on adding two Burr XII distributions is presented for modeling this type data. The graphical estimation on probability paper is illustrated, and examples of its usage are presented. The Akaike Information Criterion was used for judging the adequacy of the models presented for the numerical examples. It can be seen that the proposed model is a very competitive model for describing the bathtub-shaped failure rate lifetime data. q 2000 Elsevier Science Ltd. All rights reserved.