After a dinner with Raj, Penny, Howard and Leonard where the conversation turns, uncomfortably, toward maid of honor duties when Howard reveals that Bernadette believes she’s already been chosen to fill the role, Amy and Sheldon decide to use “metrics” to pick who will stand by them at the alter.
With Sheldon and Amy currently planning their wedding, the search is on for who will provide best man and maid of honor duties.
The idea being that they could then pretend they weren’t at fault for making the decisions, since they used numbers to make their choices.
Early in the episode, they admit to each other that they’re afraid of either picking the wrong person among their friends to fulfill the duties of the jobs, or simply not looking forward to hurting someone’s feelings when they don’t ask them.