House Democrats this week credited stimulus road and transit projects with creating or sustaining nearly 50,000 jobs. But a close look shows the estimate suffers from whats become a common malaise in the stimulus world: fuzzy math. Interviews and spot checks with states that provided job counts to the committee uncovered some glitches, in particular a reliance on raw head counts which tend to inflate the numbers by giving full- and part-time jobs the same weight and by counting the same workers two, three or four times.