The exponential distribution is a simple distribution with only one parameter and is commonly used to model reliability data. The exponential distribution is actually a special case of the Weibull distribution with ß = 1.
An important property of the exponential distribution is that it is memoryless. The memoryless property indicates that the remaining life of a component is independent of its current age. For example, a system that is subjected to wear and tear and thus becomes more likely to fail later in its life is not memoryless. Therefore, this distribution should be used when the failure rate is constant during the entire life of the product. The number of failures per unit in time is usually expressed as percent of failure per unit time, such as percent of failure per thousand hours.
An electronic component is known to have a constant failure rate during the expected life of a product. Engineers record the time to failure of the component under normal operating conditions.
A light bulb company manufactures incandescent filaments that are not expected to wear out during an extended period of normal use. They want to guarantee it for 10 years of operation. Engineers stress the bulbs to simulate long-term use and record the months until failure for each bulb.