A polyester resin and a fabrication method thereof are provided. The conductive material is electrically connected with a common electrode as one of electrodes of the electrode structure. The flexible conduit provided allows for adjustability of the conduit to the openings of the bathtub. The invention further increases precision of scores for test-takers near a cutoff by selectively allocating more reliable and accurate readers to score responses most likely to influence a test-taker’s performance classification.