Help to find a graph for AB testing analysis

I'm working on AB testing and experiment analysis and trying to figure out what this graph I heard about might be. I am new to data science and was talking to a friend about the type of analysis that can be done to analyze the results of the AB test. They mentioned a graph has something to do with determining when you have enough data to end the experiment. Hoping to figure out what it might be so I can …

ab analysis datascience graph testing