CRJ700 FLT CREW SETS THE WRONG ALTIMETER SETTING AND HAS AN ALTDEV. CTLR ALERTS THE CREW.

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I MISHEARD THE WRONG ALTIMETER SETTING FROM THE ORD ATIS OF 30.63 WHEN I WROTE IT DOWN ON THE FLT RELEASE. THE ZAU GAVE US HOLDING INSTRUCTIONS AT PIVOT INTXN AND A DSCNT FROM FL240 TO 11000 FT TO CROSS PIVOT 11000 FT AT THE SAME TIME. NEITHER ONE OF US HEARD THE CTLR GIVE US AN ALTIMETER SETTING WITH THE CLRNC. I CALLED BACK TO THE FLT ATTENDANTS AND TOLD THEM ABOUT THE HOLDING PLANS. WHEN I GOT BACK TO THE FO; I REMINDED HIM TO START HIS DSCNT AND ASSUMED THAT HE HAD RECEIVED THE CURRENT ALTIMETER SETTING FROM THE ATC AND LEFT THE FREQ AGAIN TO BRIEF THE PAX ABOUT THE HOLDING PATTERN THAT WE WOULD BE DOING. WHEN I GOT BACK ON THE FREQ; I HEARD THE CTLR ASKING ABOUT OUR ALT. WE WERE JUST ABOUT TO LEVEL OFF AT 11000 FT AND THAT'S WHAT I TOLD HIM. HE SAID WE WERE AT 10200 FT WHEN WE SHOWED 11000 FT AND THEN HE GAVE US AN ALTIMETER SETTING OF 29.63. WE REALIZED WHAT WE HAD DONE (FO HAD USED THE WRONG ALTIMETER SETTING THAT I HAD WRITTEN DOWN FROM THE ORD ATIS); PUT THE NEW ALTIMETER SETTING IN AND CLBED BACK UP TO 11000 FT AGAIN. THE CTLR DID NOT SAY ANY MORE ABOUT IT AND NEITHER DID WE. WHAT CAN BE DONE TO PREVENT THIS RECURRENCE IS TO ALWAYS MAKE SURE THAT I XCHK ALTIMETER SETTING THAT I GET WITH THE ARPT TAF ON THE FLT RELEASE TO MAKE SURE THAT I HAVE THE RIGHT ONE FOR MY DSCNTS.