Bathtub Curve is a graphical representation of the failure rate for a population of products (and not for only 1 product) over time. The curve has three parts to it
1. Infant Mortality or early failures having a decreasing failure rate
2. Useful Life or normal life with almost a constant low failure rate
3. End of Life or wear out failures having an increasing failure rate
It is a very common phenomenon used in reliability engineering
An application-oriented question on the topic along with responses can be seen below. The best answer was provided by Saravanan S on 13th December 2019.
Applause for all the respondents - Jaishree R, Kiran Kumar, Praful Bonde, Saravanan S.
Also review the answer provided by Mr Venugopal R, Benchmark Six Sigma's in-house expert.