The phrase "proven quantity" is correct and can be used in written English.
It is typically used to refer to something that has been confirmed or established as a definitive amount or measurement. Example: "The scientists' research has shown that the proven quantity of carbon emissions has increased by 10% in the past decade."
Maybe because for all that Donovan is not what he once was, he's still a much more proven quantity than the vast majority of the squad who are going.
"I think when you patch together the tenure at Janus with the record at Marsico funds, it's really hard to point to a more proven quantity within the large-cap growth arena," said Christine Benz, a senior analyst at Morningstar.
When it needs a right-handed spare outfielder, it goes for a proven quantity like Thames.
Mr. Bourdain was a proven quantity, and the new shows have some star power as well.
By contrast, he said, he is the only person in the Democratic field "who's a proven quantity" in foreign affairs.
But this guy was a proven quantity who could hit the ground running and produce results quickly".
An entrepreneur's dream is leading a startup from idea to IPO and the backing of a proven VC quantity is one way to get there.
On his latest track, "Stay," Amaral proves that quantity does not necessarily negate quality.
Angelelli and Reboul (2008) have proved that quantity: extends Newman's modularity to overlapping classes.
On current evidence, Liverpool used the £75m they received from Barcelona for Suarez - and more besides to take spending past the £100m mark - on quantity rather than proven quality.
The widely accepted importance of energy efficiency in the building sector is continuously acknowledged by the engineering and research community, as proven by the quantity and diversification of relevant modeling proposals in literature.
