| Definition -
Inserting a question mark to show that you believe
(1) that there is missing data or
(2) that the data might not be correct.
1. Use a question mark to show that there is missing data.
Rufus McDonald (1741–?)
2. Use a question mark if you believe that the information might not be correct.
Rufus McDonald (1741–1804?)
3. Inserting [sic] does not indicate editorial doubt. It shows that you know that there is something wrong with the information, but that you are going to quote it as is anyway.
According to Joe Smith, "Theirs [sic] no business like show business."