Re: Census question

I have a civil Birth Record for
Mary Ann Baird b 31 Aug. 1905
baptisim-06 Sept 1905.

Father: Samuel Baird, Mothr Rebecca Moffitt
Living on 78 Cosgrove St.,
Prish/district Urban 2, Belfast
County Antrim
Denomination Civil Paris-Antrim.

I have requested a marriage certificate from Bloomfield PresbyterianChurch where
Mary Ann age 27 married Joseph H. Dickson on
17 May 1930.

All of this said why does Mary Ann or the above parents not appear on the 1911 Irish C3ensusw. She would have been 6 yrs of age.I have spelled her name-Baird-Bard-Biard-Bird and she does not appear.

Did they just get missed?
Thank you in advance for a reply
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