Official At-Bats: Understanding Sacrifice Bunts vs. Sacrifice Flies

Question
During Jeters hitting streak, I heard an announcer say that not all sacrifices are threated the same.  
ie. a scrafice bunt that moves the runners is not an official at-bat, but a sacrifice fly ball that scores a runis an official at-bat.  
When is a sacrifice considered an official at bat and when is is not?  Do they affect on on-base-pct and batting avg?


Answer
George,

I'm not sure why the two different sacrifice scenarios would be treated differently, except that in the case of the sac fly, the batter would get the benefit of an RBI. Neither sacrifice would adversely affect a hitter's batting average, nor their on-base percentage (since the batter wouldn't reach base in either case).

Mike