(This is today's bit of advice from the book Safety Toolbox.)
Here is how any player's balls per inning (BPI) average is calculated. Over the length of a match, count the total quantity of balls made by the player. Divide that by the number of innings played. The resulting number is his BPI average for that match.
When tracked over several matches, this statistic becomes more accurate. It is a true indicator of a player's skill level. Just like a batting average in baseball, it cannot be lied about, or fudged, or ignored. For many players, the number is a sobering reality-check.
This number can be used against an opponent. When allowing an opponent to come to the table, knowing his BPI can be beneficial. Simply ensure there are more balls left on the table than his BPI. For example, if his BPI is 3 and there are 6 balls left on the table, his chances of making all six are very small. Sooner or later, he gets out of line and misses. You return to the table.
It can also help you make better shooting decisions. For example, in 8 Ball, if your BPI is 3 and there are six balls left on the table, you can make several (2 or 3) and then position a ball near a pocket while playing a defensive shot. You come back to the table with an easy starter ball, if needed, and improved chances of running out.
Against someone you are playing for the first time, use an estimate. Watch your opponent play through a couple of racks. That gives you a working BPI number. Add a little to be on the cautious side. Refine that number as the match continues.
If your opponent realizes you are using his own statistics against him, there might be some problems. Taunting a lesser player leads to ill feelings. He could take his frustrations out on you in one way or another. Explaining it to a better player gives him a weapon (and incentive) to use it against you. Keep it to yourself.
Occasionally, doing this takes nerves of steel. It's not easy to trust a number in your head, and then bet the game on the chance that the number is accurate. This takes some practice. To get comfortable, apply this information in games that are not critical. As your faith in the numbers increases, you can use them in serious competitions.