What is the burden of making a prima facie showing that age was a factor in the termination of an employee?

Once the employee makes the prima facie showing, the burden shifts to the employer to produce evidence that the termination was based on considerations other than age. Id. "This burden is one of production, not persuasion; it can involve no credibility assessment." Reeves v. Sanderson Plumbing Prods. Inc., 530 U.S. 133, 142 (2000) (citations and internal quotation marks omitted). The employer must present "a legitimate reason for the action . . . to frame the factual issue with sufficient clarity so that the plaintiff will have a full and fair opportunity to demonstrate pretext." Tex. Dep't of Cmtty. Affairs v. Burdine, 450 U.S. 248, 255-56 (1981).