Five freeze-dried PT samples are provided for vitamin D testing. The testing personnel followed the reconstitution instructions for the quality control (QC) material instead of the PT manufacturer's instructions. Reported PT values resulted in the failure of all five samples tested, with each failed result being approximately half of the anticipated acceptable range. What error was most likely attributed to the testing failures? Please select the single best answer Incorrect reporting units entered Incorrect reconstitution of samples Testing of incorrect analyte Reporting of incorrect test method