How to write a bid medical device service life average trouble free operation time

Tender medical equipment service life average trouble-free operation time is defined as under the specified conditions and the specified time. According to the query related information, the ratio of the total number of life units of the product to the total number of failures. Mean trouble-free operating time is the mathematical expectation of the repairable product working time between two adjacent failures, i.e., the average of the working time between each of the two adjacent failures, which corresponds to the ratio of the working time of the product to the number of product failures during this period of time. In fact, the average failure-free working time is the average life, only this average life and the recognized average life is different, does not mean the average time of the demise of the product and the end of the average time of the product, but only the average time of the product can work normally.