Whenever you find an index entry for a record or a transcription of a record, view the actual item. Transcribers and indexers make mistakes, leave items out, etc. We’ve mentioned this before, but it is worth repeating. This post on the German parish records at Ancestry.com makes the point pretty well. 
Is there really one informant on that record? Is it possible that when the information was being provided for the birth record, death certificate, or other document that more than one person was giving information to the clerk? Don’t assume the same person provided every piece of information on that record you are using.
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