1. A method comprising: retrieving a first targeting model and a second targeting model for targeting content to users of an online system, the first targeting model and the second targeting model including a collection of rules that control how characteristics are mapped to users of the online system; predicting, using the first targeting model, a first group of users of the online system as candidates to be in a targeting cluster associated with a characteristic of interest; predicting, using the second targeting model, a second group of users of the online system as candidates to be in the targeting cluster; determining a first set of users of the online system that are not part of the first group of users, and a second set of users of the online system that are not part of the second group of users; providing surveys to the first set of users and the second set of users, the survey asking whether a user should be associated with the characteristic of interest, the surveys testing whether the first and second targeting models correctly predicted that the user should not be included in the targeting cluster associated with the characteristic of interest; determining a first subgroup of the first group of users and a second subgroup of the second group of users, the first subgroup and second subgroup composed of users that are associated with the characteristic of interest; providing a preferences tool to the first subgroup and the second subgroup, the preferences tool prompting a viewing user to modify preferences listed for the viewing user, the preferences tool testing whether the first and second targeting models correctly predicted that the viewing user should be included in the targeting cluster associated with the characteristic of interest; and scoring the first targeting model and the second targeting model based at least in part on one or more responses to the surveys and one or more responses to the preferences tool, the score measuring precision and recall of the first and second targeting models.