Most of the stats you'll find in searches on our Football Stathead site are straightforward stats from boxscores. However, there are a few calculated advanced stats not found on other websites that you might not be familiar with. Here's a quick rundown with definitions of those stats:
ANY/A - adjusted net yards per passing attempt: (pass yards + 20*(pass TD) - 45*(interceptions thrown) - sack yards)/(passing attempts + sacks).
AV - approximate value. This is our attempt to put a single number on each player-season since 1960 so that we can (very approximately) compare across years and across positions. See this blog page for all the details.
AY/A - adjusted yards per passing attempt: (pass yards + 20*(pass TD) - 45*(interceptions thrown))/(passing attempts). This stat was introduced, and the reasoning behind it thoroughly explained in a book called The Hidden Game of Football, by Bob Carroll, Pete Palmer, and John Thorn.
NY/A - net yards per passing attempt: (pass yards - sack yards)/(passing attempts + sacks)
Game-Winning Drives - QB must lead an offensive scoring drive in the 4th quarter or overtime that puts the winning team ahead for the last time.
4th Quarter Comebacks -QB must lead an offensive scoring drive in the 4th quarter, with the team trailing by one score, though not necessarily a drive to take the lead. Only games ending in a win or tie are included.
For more information on Game-Winning Drives and Fourth Quarter Comebacks, see this three-part series: