CNN rated as “true” Mitt Romney's claim that his tax proposals would create about 7 million jobs, noting that the study on which the Republican presidential candidate based his claim makes certain assumptions. But in rating the claim true, CNN assumed facts it did not possess -- and that the study's author admitted he lacked.

During an interview with CNN anchor Wolf Blitzer, Romney said that his tax proposal was “scored by people at Rice University as creating 7 million new jobs.” What Romney omitted to say, however, is that John Diamond, the economist who conducted the Rice University study, had no way of truly scoring the plan.

As National Journal explained, Diamond “couldn't model the full Romney plan, because the Republican's campaign refuses to identify, even to him, which tax deductions and credits they would cut to make the plan revenue-neutral.” The article continued:

“They didn't give me a whole lot of guidance,” he said.

So Diamond filled in the blanks with largely generic assumptions and noted in his analysis that the specifics could change his results. He also assumed that Romney -- contrary to his stated campaign position -- would allow the Bush tax cuts to expire and then impose his 20 percent across the board rate reduction from there.

Diamond's final conclusion was that Romney's reform would add 5.4 percentage points to projected gross domestic product growth over the next decade and would result in 6.8 million new jobs.

The Journal further noted that “Diamond didn't analyze how the plan would affect the distribution of the tax burden across income levels” but guessed that “it's not possible” to avoid raising taxes on lower- and middle-income Americans -- something Romney maintains he would not compromise on.

In his fact-check, CNN anchor John Berman noted that “Diamond says that since Romney does not make clear how he would pay for his plan, Diamond had to make certain assumptions and depending on what deductions and loopholes Romney closes, that could change the results.”

Berman concluded, however:

BERMAN: Our verdict here is true with important qualifications on the claim that there is a study that says his plan would add 7 million jobs. It only adds 7 million according to the study if you assume certain details that Romney simply doesn't provide.

But the purpose of fact-checking isn't to assume what is true and what is false -- it is to evaluate factual statements based on relevant information and actual available details. But as Berman acknowledged, he did not have that evidence -- and Diamond has admitted he couldn't accurately score Romney's full plan.