; (B) in evaluating any report, information, or analysis, take into consideration whether the results are statistically significant, are capable of replication, and withstand peer review; and (C) consider an association between the occurrence of an illness in humans and exposure to an herbicide agent to be positive for purposes if the credible evidence for the association is equal to or outweighs the credible evidence against the association. (c) Definitions For purposes of this section: (1) The term covered period means the period beginning on January 1, 1958, and ending on the latter of the following dates, as determined by the Secretary: (A) December 31, 1999. (B) The date on which the last member of the Armed Forces departed from official duty in the Panama Canal Zone. (2) The term herbicide agent means a chemical in an herbicide, including Agent Purple and Agent Orange. . (b) Clerical amendment The table of sections at the beginning of such chapter is amended by inserting after the item relating to section 1118 the following new item: 1120A. Presumption of service connection for illnesses associated with service in the Panama Canal Zone. .