The basic concept is that scoring a goal on a tough defense is better than scoring a goal against a sieve. Similarly, allowing a goal to high powered offense is less shameful than giving up a goal to an inept one. How to convert this idea into math? Using the chart from the previous post, add up the percentages.
To figure out the offensive component, we need to compare how many goals each team scored against an opponent versus how many goals that opponent allowed in total. To do this we move left to right, dividing each number by the total on bottom.
Algeria Offense
Scored 3 of 4 total goals against Egypt (3/4 = .750)
Scored 3 of 5 total goals against Zambia (3/5 = .600)
Scored 3 of 8 total goals against Rwanda (3/8 = .375)
.750 + .600 + .375 = 1.725 total offense
Egypt Offense
Scored 3 of 4 total goals against Algeria (3/4 = .750)
Scored 2 of 5 total goals against Zambia (3/5 = .400)
Scored 4 of 8 total goals against Rwanda (3/8 = .500)
.750 + .400 + .500 = 1.650 total offense
For defense we go the other way, moving down the columns and comparing against the totals on the right.
Algeria Defense
Allowed 3 of 9 total goals scored by Egypt (3/9 = .333)
Allowed 0 of 2 total goals scored by Zambia (0/2 = .000)
Allowed 1 of 1 total goals scored by Rwanda (1/1 = 1.000)
.333 + .000 + 1.000 = 1.333 total defense
Egypt Defense
Allowed 3 of 9 total goals scored by Algeria (3/9 = .333)
Allowed 1 of 2 total goals scored by Zambia (1/2 = .500)
Allowed 0 of 1 total goals scored by Rwanda (0/1 = .000)
.333 + .500 + .000 = 0.833 total defense
For offense, the higher the number the better. For defense, the lower the number the better. That means to get the most meaningful single number, subtract defense from offense, and the highest resulting total is “best.” (Subtracting a smaller number gives a higher result, keeping the scale set to higher = better.)
Algeria
1.725 offense - 1.333 defense = 0.392
Egypt
1.650 offense - 0.833 defense = 0.817
The higher the number the better, meaning Egypt wins the tiebreaker.