Let's start with Offensive Efficiency.
A team's offensive efficiency is the amount of points it scores per 100 offensive possessions.
OE = (Points scored * 100) / Possessions
Let's stick with the 2018 NCAA Tournament First Round game between Marshall and Wichita State.
Marshall had 72.47 possessions and scored 81 points. Its offensive efficiency was 112.
OE = (81 * 100) / 72.47 = 111.77
Wichita State scored 75 points over 72.08 possessions for an OE of 104.
OE = (75 * 100) / 72.08 = 104.05
A team's defensive efficiency is the amount of points it allows per 100 defensive possessions.
DE = (Points allowed * 100) / Possessions
Following our example above, Marshall's defensive efficiency is 104. Marshall allowed 75 points over 72.08 possessions.
DE = (75 * 100) / 72.08 = 104.05
Wichita State's defensive efficiency is 112. The Shockers allowed 81 points over 72.47 possessions.
ODE = (81 * 100) / 72.47 = 111.77
Notice this is the inverse. An opponent's offensive efficiency equals a team's defensive efficiency. A team's offensive efficiency equals their opponent's defensive efficiency.
Remember this is the number of points scored or allowed per 100 possessions. Offensive efficiency isn't an indication of how many points a team scores. Defensive efficiency doesn't suggest how many points a team allows.
The final score of this game was Marshall 81, Wichita State 75. Not 112-104.
The average college basketball game features around 70 possessions. In our example above, the game featured about 72 possessions.
The Offensive Efficiency numbers are high because the statistic is over 100 possessions. Not 72 or 70.
Don't confuse points-per-game with offensive or defensive efficiency.
A team's efficiency can be broken into four factors. Remember those factors?
Getting to the foul line
Let's continue with this same game as an example.
Marshall turned in an offensive efficiency of 112.
eFG% = 54%
OR% = 20%
TO% = 12.5%
FTRate = 36.7
Marshall made a high percentage of shots, avoided turnovers 87% of the time, and frequently got to the foul line.
Wichita State posted an offensive efficiency of 104.
eFG% = 48%
OR% = 41%
TO% = 21%
FTRate = 26.2
While Wichita State rebounded a lot of their missed shots and shot the ball decent, Marshall was just a bit better.
This a good reason why Marshall won the game by 6 points. A higher offensive efficiency and a lower defensive efficiency than their opponent.