I propose we use this definition of Net Run Rate (NRR) from the ICC Trophy regulations:
A team’s net run rate is calculated by deducting from the average runs per over scored by that team over the relevant portion of the tournament, the average runs per over scored against that team over the relevant portion of the tournament.
In the event of a team being all out in less than its full quota of overs, the calculation of its net run rate shall be based on the full quota of overs to which it would have been entitled and not on the number of overs in which the team was dismissed.
Example, three 20-over matches between teams A, B and C:
A (100 for 6 off 15 overs) beats B (95 for 8 off 20 overs)
B (110 for 4 off 20 overs) beats C (100 all out off 18 overs)
C (120 for 3 off 16 overs) beats A (119 for 8 off 20 overs)
Net run rate for A = (100 + 119) / (15 + 20) - (95 + 120) / (20 + 16) = 6.25 - 5.97 = +0.28
Net run rate for B = (110 + 95) / (20 + 20) - (100 + 100) / (15 + 20) = 5.125 - 5.715 = -0.590
Net run rate for C = (100 + 120) / (20 + 16) - (110 + 119) / (20 + 20) = 6.111 - 5.725 = +0.386
Note the use of 20 rather than 18 for C's innings against B because they were all out before using up their 20 overs.
So C would win the three-cornered tournament on net run rate. If they had taken an extra 4 balls to beat A then their net run rate would have dropped to 0.274 and so A would have won.
