Amortized analysis
In computer science, amortized analysis is a method for analyzing a given algorithm's complexity, or how much of a resource, especially time or memory, it takes to execute. The motivation for amortized analysis is that looking at the worst-case run time can be too pessimistic. Instead, amortized analysis averages the running times of operations in a sequence over that sequence.[1]: 306 
As a conclusion: "Amortized analysis is a useful tool that complements other techniques such as worst-case and average-case analysis."[2]: 14 
https://en.wikipedia.org/wiki/Amortized_analysis