• Reliability Over Time. The probability that a product will operate successfully over a given period of time (or number of cycles) without any failures. For example, there is a 94 percent chance that the product will operate successfully after 7 months of operation.

• Probability of Being in a Failed State at a Given Time. If the component is non-repairable, then it is equivalent to the probability that a product is in a failed state at a particular point in time. Also known as unreliability, the probability of failure is 1.00 minus the reliability. For example, there is a 6 percent chance (1.00 - 0.94) that the above product will have failed after 7 months of operations (and a 94 percent chance that it will operate successfully).

• Mean Life. The average time that the products in the population are expected to operate before failure. This metric is referred to as the Mean Time to Failure (MTTF).

• Failure Frequency. The number of failures per unit time that can be expected to occur for the product.

• Failure Rate. The rate of occurrence of failures. This value is normally expressed as failures per million hours, but it can also be expressed as a FIT Rate (Failures in Time) or failures per billion hours. Failure rate is basically the anticipated number of times that an item fails in a specified period of time. For example, if a component has a failure rate of 2 failures per million hours, then it is anticipated that the component fails 2 times in a million hour time period.

• Warranty Time. The estimated time when the reliability will be equal to a specified goal. For example, the estimated time of operation is 9 months for a reliability of 96 percent.

• B-Life. The estimated time when the probability of failure will reach a specified point. For example, if 10 percent of the products are expected to fail by 3 years of operation, then the B-10 life is 3 years. (This is the equivalent to a warranty time of 3 years for a 90 percent reliability.)