The average time between consecutive failures in a system or component during a specified period is known as the mean time between failures (MTBF). 

Evaluations of planning are based upon the thoroughness and effectiveness of processes including the information used.

A unit level test plan should be input to a system or integration level test plan. 

Quality control relates to a specific product or service. 

When you believe the problem has been solved, it is logical to assume that your customer also agrees.