The Supreme Court on Tuesday continued to disappoint big business’s efforts to curb class-action lawsuits and upheld a nearly $6 million award to workers at a Tyson Foods pork-processing plant in Iowa.

In a 6-to-2 ruling, the court rejected Tyson’s contention that the more than 3,300 workers at the plant should not have been able to use statistical averages to prove that they were not paid what they were due. The court did not rule on a second argument offered by Tyson, that some workers who had not been underpaid might benefit from the award.

Workers in the Storm Lake, Iowa, plant had alleged that they were not properly compensated for the time they spent putting on required protective gear and walking to their workstations. A jury agreed.

Writing for the majority, Justice Anthony M. Kennedy rejected industry’s call for what he said would be a broad rule banning what is called “representational evidence” in class-action suits.

The admissibility of statistical samples as evidence, he said, “turns not on the form a proceeding takes — be it class or individual action — but on the degree to which the evidence is reliable in proving or disproving the elements of the relevant cause of action.”

The Tyson case was one of several this term that asked the court to cut back on class actions. But in January, the court ruled in Campbell-Ewald Co. v. Gomez that a company may not ask a court to throw out a potential class-action lawsuit simply by offering the lead plaintiff all that the plaintiff has sought.

Had the ruling gone the other way, mounting such lawsuits would have become harder, because a defendant could moot a proceeding by removing the plaintiffs one at a time.

[Supreme Court rules for plaintiffs in class-action case] In the Tyson case, the company claimed that the thousands of current and former plant workers who brought the suit did not have enough similarities in their duties to be able to use statistical averages. The workers sought to prove that they had not been compensated for overtime accumulated “donning and doffing” protective gear and doing other tasks necessary for their work.

The company asked the court to extend its reasoning in Wal-Mart Stores v. Dukes, in which the court ruled for the corporate giant in a class-action suit filed on behalf of 1.5 million female employees who had alleged discrimination.

Kennedy said the Wal-Mart decision remained good law. He said that that suit had failed because the workers’ job descriptions were not close; that was not the case for the Tyson workers, he said.

The court also relied on a nearly 70-year-old precedent that says that when the company has kept poor records of the time required for the tasks required of workers — and Tyson acknowledged that was the case here — the workers are allowed to use statistics to calculate the lost time.

The court did not rule on Tyson’s argument that some workers who were not undercompensated will be allowed to benefit from the award. Kennedy said the issue was premature, because “the damages award has not yet been disbursed, nor does the record indicate how it will be disbursed.”

Chief Justice John G. Roberts Jr. joined Kennedy and the court’s liberals in the ruling. But he wrote a separate opinion “to express my concern that the district court may not be able to fashion a method for awarding damages only to those class members who suffered an actual injury.”

Justices Clarence Thomas and Samuel A. Alito Jr. dissented. They concluded, in part, that the workers were not similarly situated.

“Our precedents generally prohibit plaintiffs from maintaining a class action when an important element of liability depends on facts that vary among individual class members,” Thomas wrote.

The case is Tyson Foods v. Bouaphakeo.