Whatever the reason, Mr. Quayle remains an unknown quality to almost half of the electorate, despite [...]
And from a New York Times blog post:
The Huskers (30-1) enter the N.C.A.A. tournament as an unknown quality to most fans.
Yes, I know, the following question might be Not A Real Question, but I'm under the impression that unknown quality doesn't fit the meaning of the above sentences.
Yes, and always in the case I'm right, two sentences quoted from The New York Times are not enough to get definitive conclusions, but is there some common problem among English speakers in confusing "unknown quality" with "unknown quantity"?