Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Mean sensitivity estimates (ap) for Group 11 (between .25 and .32) were similar to the mean sensitivity estimate of .20 found by Lie and Alsop (2009), who used a similar task and sample of participants.
Category: