ACR PNF COPIED ATIS ALTIMETER SETTING INCORRECTLY. FLC RPTED THAT THE ERROR WAS NOT CAUGHT BY ANYONE; UNTIL APCH CTLR INTERVENED; DURING THE INITIAL APCH PHASE.

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ON APCH TO DTW LEVEL AT 4000 FT APCH CTL TELLS US TO MAINTAIN 4000 FT WE REPLIED THAT WE WERE AT 4000 FT SO HE SAID CHK ALTIMETER 29.55. THE FO HAD COPIED THE ATIS AND WROTE DOWN 29.94. WE CORRECTED THE ALTIMETER AND SHOWED A 400 FT DIFFERENCE THE CTLR HAD A 500 FT ON HIS SCOPE. HOWEVER OUR ALT WAS CLRLY 400 FT DIFFERENT. I TUNED THE RADIO #2 TO ATIS AGAIN AND THE ATIS WAS RPTING 29.54. THIS ERROR IN RECORDING DOWN THE ATIS WAS NEVER CAUGHT BY ANYONE UNTIL THE FINAL APCH CTLR. ZOB WAS BUSY AND WHEN ORIGINALLY CLRED TO 12000 FT HE HADN'T GIVEN US AN ALTIMETER SETTING AND ALSO NEVER NOTICED THE ERROR IN ALTITUDE. THEN ON THE FIRST DTW APCH CTL FREQ AGAIN THE SAME THING. AND NOT UNTIL WE WERE LEVELING AT 4000 FT DID THE LAST APCH CTLR NOTICE THE ERROR. WITHOUT AN ALTIMETER SETTING FROM ATC IN THE DSCNT OR ANYWHERE ELSE WE HAD NO XCHK TO CATCH THE ERROR. THE ALTIMETER SETTING BY ATC IS NORMAL; HOWEVER WORKLOAD AND OVERSIGHT CONTRIBUTED TO THE MISS BY THE FO. P.S. THE FO SAID HE LISTENED TO THE ATIS TWICE. SUPPLEMENTAL INFO FROM ACN 304877: ATIS INFO FOR DTW RECEIVED 100 MI FROM ARPT. ON FINAL FOR RWY 21R AT DTW; THE SECOND APCH CTLR QUESTIONED OUR ALT. WE WERE AT 4000 FT MSL BUT ACTUAL WAS 3600 FT WHEN HE PROVIDED; AT THIS TIME; THE CORRECT ALTIMETER SETTING.