What is "double blind"

n. a test procedure in which the identity of those receiving the intervention is concealed from both the administrators and the subjects until after the test is completed; designed to reduce or eliminate bias in the results

"Double Blind" is the 23rd episode of the tenth season of the American police procedural drama NCIS, and the 233rd episode overall. It originally aired on CBS in the United States on May 7, 2013. The episode is written by Christopher J. Walid and Steven D. Binder and directed by Dennis Smith, and was seen by 17.56 million viewers.