Trying to rebound from their last-second road loss to the Broncos, the Steelers flew to Paul Brown Stadium for a Week 8 AFC North brawl with the Cincinnati Bengals.  In the first quarter, Pittsburgh trailed early as Bengals kicker Shayne Graham managed to get a 31-yard field goal.  Fortunately, the Steelers took the lead with QB Ben Roethlisberger completing a 21-yard TD pass to WR Hines Ward.  In the second quarter, Pittsburgh increased its lead with Roethlisberger and Ward hooking up with each other again on a 6-yard TD pass to lead 14-3.  With 2:16 left in the second quarter on 4th-and-1 at the Steelers 2, Cincinnati chose to kick a 20-yard field goal and received loud boos from the hometown crowd upon successfully doing so.  In a similar situation two minutes later, Steelers RB Willie Parker ran 1&#160;yard into the end zone to put the Steelers up 21-6 at the end of the first half. After a scoreless third quarter, the Bengals tried to make a fourth quarter comeback as QB Carson Palmer completed a 9-yard TD pass to WR T. J. Houshmandzadeh.  Pittsburgh wrapped up the victory with kicker Jeff Reed nailing a 40-yard field goal.
Question: How many points did Pittsburgh lead by at the half?
Answer: 15