A bathtub curve illustrates the failure rate of products by describing three life phases: high initial failures, a period of low constant failures, and wear-out failures. Which option best describes these phases?

• A. A bathtub curve starts with a high failure rate during early life, then drops to a low rate, and increases again during wear-out.
• B. It shows a constant high failure rate throughout life.
• C. It indicates failures occur randomly with no pattern.
• D. It shows a steady decrease in failure rate from start to end.

Answer: (A)

The bathtub curve shows how a product’s failure rate changes over its life, with three distinct phases: a high initial failure rate due to early-life defects (infant mortality), a long period of low, roughly constant failures during useful life, and a wear-out phase where failures rise again as the product ages. The option that describes starting with a high failure rate, then dropping to a low rate, and increasing again during wear-out matches this sequence exactly. The other descriptions don’t fit because they imply a constant high rate, no pattern, or a steady decrease in failures, none of which capture the characteristic rise in failures as components age.