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Definition – What is a “safe lead” in basketball?
“Safe lead” is a formula to calculate the chance that a lead in a game is safe (the leading team is almost certain to lead). It is intended for college basketball games.
The formula was developed by baseball statistician Bill James.
Formula – How to calculate a safe lead
- Use the number of points the leading team is ahead.
- Subtract 3
- Add 1/2 point if the leading team has the ball. Subtract 1/2 point if the trailing team has the ball.
- If the number is less than 0, make it zero.
- Square the number
- If the result is more than the number of seconds left in the game, the lead is safe. If it is not the lead is not safe.
Example
A team is up by 18 points (84 to 66) with 3 minutes and 51 seconds left to go. The trailing team has the ball.
- Number of points the leading team is ahead: 18
- Subtract 3: 15
- Add 1/2 point if the leading team has the ball. Subtract 1/2 point if the trailing team has the ball: 14.5
- If the number is less than 0, make it 0: 14.5
- Square the number: 210.25
- If the result is more than the number of seconds left in the game, the lead is safe. If it is not the lead is not safe: 3 minutes 51 seconds = 231 seconds.
As 210.25 is less than 231 seconds, the lead is not safe. If the leading team had possession of the ball, the number would calculated to 240.25 and the lead would be considered safe.
Sources and more resources
- “The Lead is Safe” by Bill James – The logic and formula behind the “safe lead” theory by Bill James.