erroneous conjecture

He had guessed that Chellish would be questioned but his fears had been based on erroneous conjectures.

As she explains to Smith Williams in another letter at the Morgan, she hopes to "set at rest all erroneous conjectures respecting their identity."

He made liberal use of capitals for emphasis and excelled in some quasi-etymological erroneous conjectures (such as substituting 'Omr ("life") for 'Omar Khayyam).

The supposed "White Dodo" (or "Solitaire") of Réunion is now considered an erroneous conjecture based on contemporary reports of the Réunion Ibis and 17th-century paintings of white, Dodo-like birds by Pieter Withoos and Pieter Holsteyn that surfaced in the 19th century.