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:To determine whether the arcometer constitutes a reliable method, data collection was organized so as to provide three types of information: (1) the validity of the instrument based on a comparison of the measurements obtained with the arcometer and X-ray (n=52) on the same day and in the same place; (2) the intra-evaluator reproducibility of the instrument based on the comparison of the measurements obtained with the arcometer by the same evaluator on two occasions at an interval of seven days (n=15); and (3) the inter-evaluator reproducibility of the instrument based on the comparison of the measurements obtained by two different evaluators on the same day and in the same place (n=30).
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