Bill Connelly, the author of Study Hall: College Football, Its Stats and Its Stories, and a regular contributor at SB Nation, has coined five statistics that are vital to success in college football.

The list includes: Explosiveness (yards per play), Efficiency (Success Rate), Finishing Drives (points per trip inside the 40), Turnover Margin and Field Position.

In preparation for the upcoming season, Blue & Gold Illustrated is reviewing the results from last year's Notre Dame totals and looking ahead to 2015.

Today's feature looks at factor No. 4 on our list - Turnovers.

Explanation: Ahh, turnovers. This is always a fun one. There's often a lot of luck involved in this stat, maybe because of something as simple as the ball in this sport is oddly-shaped, pointier than most. And a bounce one way or the other can end up very favorably for your team - or a disaster.

Sure, depending on factors like your style of play, or the throwing accuracy and decision-making ability of your quarterback, you can try to control this a bit. But look at all the different outcomes that can happen when one fumbles the ball. Sometimes it can bounce right back into friendly hands - other times, the hands of the opponent. Or sometimes the right person is standing in just the right place to dive on the ball - sometimes there's a huge pileup and fight for it.

A pass can be tipped at the line high into the air, sometimes right toward a defender for an easy interception - other times, it's tipped right to empty space. A receiver can take his eyes off an incoming pass for just a second, and it bounces off his hands or chest right into a defender's - or it falls harmlessly to the ground.

Again, not saying that teams are completely helpless to the turnover, entirely victims of simply a good or bad day. Only saying luck can be involved a lot more than we usually acknowledge.

According to Connelly's research, the average turnover is worth about five points, considering the field position given away by the offense and gained by the defense for their team. Context is obviously important here, because not all turnovers are created equal - for example, sometimes a quarterback throws a Hail Mary at the end of the first half that's intercepted in the end zone as the clock expires.

The important number to remember for fumbles is, due to sheer luck of the bounce, the average recovery rate is around 50 percent. If your team recovers more than half of their fumbles, they're a bit fortunate. Recover less than half, and you're obviously unlucky. As for interceptions, the average ratio is around one in every five passes defensed are picked off.

Again according to Connelly, a plus 1 turnover margin gives you a ~65% chance to win. A plus two and plus three margin both round to a 79 percent win probability, so they're about the same. You don't need numbers to know that a plus four margin or higher likely doesn't end well for your team.

Notre Dame won the turnover margin in four contests in 2014, winning all four of those games. They lost the turnover margin in five games, losing three of those. They finished 2-2 in the four games there was a tie.

The most interesting game last year was a 31-15 win over Syracuse. Notre Dame lost the turnover margin 5-1 against the Orange, but still managed to win by more than two touchdowns - a credit to their defense that game for buckling down when it needed to. Syracuse crossed the Notre Dame 40-yard line six times, but only managed one touchdown and one field goal in those six drives.

Overall, the Irish finished the 2014 season with a -3 turnover margin. They fumbled the ball 24 times and lost 12 - right on average - while their opponents fumbled 13 times and lost 7 (close enough to the average.) Notre Dame quarterback Everett Golson took a lot of heat for his fumbles, losing control of the ball 12 times and the defense recovering eight of those (a bit unlucky,) but also threw an additional 14 interceptions. If new quarterback Malik Zaire can trim down from Golson's 22 total turnovers in 2014 (nearly two a game,) that'd be a good sign for this year.

Other Five Factors Reviews:

No. 1 - Explosiveness

No. 2 - Finishing Drives