A significant prerequisite for class action is individual standing. According to Adair v. Sorenson, "a court must assess standing to sue based upon the standing of the named plaintiff and not upon the standing of unidentified class members." Furthermore, "only after the court determines the issues for which the named plaintiffs have standing should it address the question whether the named plaintiffs have representative capacity, as defined by Rule 23(a), to assert the rights of others." Thus, standing is vital to class certification and all stages of class action litigation.
Commonality is also a necessity of class action litigation. In order for there to be “representation” for the group, there must be some facts that are "common" to the group. It is important to note that the commonality requirement is not high or excessive. In essence, “the rule requires only that the resolution of common questions affect all or most of the class members.” In other words, the test for commonality is "qualitative rather than quantitative, that is, there need be only a single issue common to all members of the class.” Moreover, there will not be class certification if there is a significant conflict of interest between the class members and the class representatives. The plaintiffs must “possess sufficient similarity of interests to the absent class members, to make them proper class representatives.”
For class certification, Rule 23 determines that “the class must be of sufficient numerosity to make joinder impracticable.” The numerosity requirement is evaluated on a case-by-case basis. Therefore, the court has wide discretion and loose parameters when considering numerosity, and they take into account the unique facts and context of each case. In general, when the class includes forty or more members, the numerosity requirement is satisfied. If the class includes twenty-one or fewer members, then the numerosity requirement is not satisfied. The main issue that the court considers is whether the class is too large to make joinder impracticable.