I fully agree with Sharon. Many times it depended on who provided the information and if it came from a neighbor who really did not know the family well she might have said something like "I think" and the census taker took it to be totally accurate.
The other issue might have been "language" . If the neighbor did not speak English well the census taker might have had a problem understanding what was said and rather than asking again just wrote what he thought he heard. Does the information on the third child might be what you otherwise know to probably be fact?
