A class action antitrust suit alleging cable companies' violations of Sections 1 and 2 of the Sherman Act in regard to the provision of cable television programming services, Rule 23(b)(3) certification by the district court is affirmed where the court did not exceed its permissible discretion in determining that plaintiffs established by a preponderance of evidence that they would be able to prove through common evidence a class-wide antitrust impact and a common methodology to quantify damages on a class-wide basis.