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:High-risk students exposed to the intervention were 80% less likely to take up cocaine use relative to a no-intervention control group, 30% less likely to take up cannabis use, and 50% less likely to take up other drug use (Conrod et al., 2010).
Category: