'unsubstantiated assumption' is correct and usable in written English.
This phrase can be used to describe ideas that are taken to be true but lack evidence to back them up. For example, "The manager's decision was based on an unsubstantiated assumption that the new hire was capable of doing the job."
[4] Mr. Kristof's reliance on a singular source with a known bias on this topic, to stand-in for actual law and policy, along with his unsubstantiated assumption (discussed above) regarding a pattern of parental misbehavior, appear to form the basis for his conclusion that the SSI program is a failed one deserving of major cuts.
Or, what if he's correct in his unsubstantiated assumption.
She carried on her mission to convince heterosexuals and homosexuals alike that homosexuality is not an illness, stating in a letter in 1967: "I keep trying to convince people in the movement that the charge of sickness is perhaps our greatest problem... we can't really progress in other directions until the unsubstantiated assumption of sickness...is demolished!
There is a tacit but unsubstantiated assumption that targets that are genetically vulnerable are also chemically vulnerable and vice versa.
However, one made an unsubstantiated assumption that awareness of the observer increases as the audit progresses, 15 and the other used a survey to determine self-reported awareness of being observed.
This review establishes that previous investigations may have failed because of their unsubstantiated assumption that, in a well-working balanced occlusion, force is only exerted perpendicular to the occlusal plane, allowing the denture to sit firmly on its foundation.
"You don't have to be Einstein to figure out which game is a far more impressive spectacle," O'Neill commented, making unsubstantiated assumptions about the father of modern physics' stance on watching bulky men fall over a lot.
The Democrats say Mr Obama's ahead in the key states; the Republicans counter that the national polls are tied, and that the state polls suffer from unsubstantiated assumptions and methodological deficiencies.
On local election results night, these unsubstantiated assumptions included the Conservatives doing very badly, when the party ended up the largest in local government in England; and that people voted for the BNP in Burnley for reasons other than simple racism, according to Liddle.
These unsubstantiated assumptions were not repeated in CBO's extensive (167-page) examination in December, 2009, of the factors involved in speculating on the effects of possible reforms.
Such labels are convenient but they are based on unsubstantiated assumptions, passed down for decades since the label first became trendy, about selfish "me-me-me what-ever" people who won't just join a church already.
