ACR B737 UNDERSHOT ASSIGNED ALT OF 11000 FT BY 800 FT DUE TO WRONG ALTIMETER SETTING.

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WE WERE DOING THE BONHAM 2 ARR VIA TUL VOR INTO DFW ARPT. I WAS THE FO AND PF. AS EXPECTED; WE WERE TOLD TO CROSS KARLA INTXN AT 11000 FT. AS WE DSNDED THROUGH FL180; I ASKED FOR THE DSCNT/APCH CHKLIST. THE CAPT HAD EARLIER COPIED THE ATIS FOR DFW ARPT AND GAVE ME AT THAT TIME WHAT HE SAID WAS THE RPTED ALTIMETER SETTING. WE LEVELED OFF AT INDICATED 11000 FT A FEW MI PRIOR TO REACHING KARLA INTXN. NOT TOO LONG AFTER APCH CTL CAME BACK ON AND TOLD US THAT HE WAS SHOWING US LEVEL AT 11800 FT AND AT THE SAME TIME GAVE US THE CURRENT ALTIMETER SETTING. WE IMMEDIATELY KNEW THAT THE CAPT HAD COPIED A TOO HIGH ALTIMETER SETTING FROM ATIS WHICH HE THOUGHT WAS CORRECT. WE COPIED THE CORRECT ALTIMETER SETTING AND I IMMEDIATELY RESET MY ALTIMETER AND DSNDED DOWN TO 11000 FT. PRIOR TO CORRECTING; IT SHOWED 11000 FT AND AFTER I RESET; IT WAS 11800 FT -- JUST LIKE APCH HAD TOLD US. NOTHING ELSE WAS SAID ON THE RADIO CONCERNING OUR LEVELOFF AT 11800 FT. NEXT TIME WHEN ATC GIVES US AN ALT BELOW FL180; I WILL MAKE A NOTE ABOUT THE ALTIMETER SETTING; SO I CAN COMPARE IT WITH WHAT THE ATIS WILL GIVE US. I WILL ALSO PAY MORE ATTN TO WHAT ALTIMETER SETTING ATC GIVES TO OTHER TFC IN OUR AREA.