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:…or sports (Stewart et al., 2001), although older adults are more likely to engage in the former type of physical activity (duration ratio = 3:1; Yasunaga et al., 2006), and (b) the accelerometer becomes less accurate when measuring lowintensity physical activity such as general household…
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