Computer ratings for college and high school are based on a margin-of-victory calculation and a 10-goal limit (correction).
Goal Margin
The local computer rating adheres to one criterion: The goal margin of victory equals the difference in power ratings between the two opponents if the game were to be played on a neutral field.
When played at the site of one of the teams, a home field advantage (HFA) is added for that team. HFA is determined by averaging the home minus away scores for all games played in the local region.
PR1 - PR2 + HFA = score1 - score2
Error
Ideally, if you (a) subtract the power ratings of the two teams and (b) account for home field advantage ('+' if the designated team is at home and '-' if the designated team is away), the result
should be equal to difference in the actual game score. This will only seldom occur, of course, and each game produces an error as follows:
If Err > 0, then the designated team played above its computer rating.
If Err < 0, then the designated team played below its computer rating.
Thus, if Team A plays Team B, and Team A has a power rating of 90 and team B has a power rating 80, then A would be predicted to beat B by 10 goals if the game were played at a neutral site. The
power ratings are based on all games a team plays and averaged for total performance. The computer program iterates on all teams for all games such that the average error for all teams goes to zero.
All teams start even at the beginning of the season. Past seasons performance is not considered. Early in the year, the program has no knowledge of favorites or underdogs and thus has no bias.
However, it takes 5 to 6 weeks for the computations to become meaningful. The objective of the computer rating scheme is to insure that the iterative final power rating for all teams produces a
sum over all games for each team such that the
sum of the local error = 0.00. In other words, the power rating is the average of a designated teams performance over all games and the magnitude of the '+'s and '-'s balances out as the sum
of errors goes to zero when all local games a team plays are considered.
Opponent Score Opp PR Home 1 Lynbrook 15 6 93.52 away 2 Chaminade 14 12 96.35 neut 3 Manhasset 20 8 90.06 away 4 MacArthur 20 5 86.79 home 5 Floral Park 15 0 87.53 away 6 Syosset 21 3 87.38 home 7 Duxbury 9 3 97.40 away 8 Division-Levittown 20 2 82.66 away 9 Carey 24 2 81.37 home 10 Great Neck No 18 3 80.48 away 11 Wantagh 13 10 95.10 home 12 Port Washington 20 6 87.94 away 13 Lawrence 15 7 88.12 away 14 Southside 17 2 85.26 home 15 Long Beach 11 3 87.02 away 16 Southside 18 4 85.26 home 17 Floral Park 17 9 87.53 neut 18 Wantagh 8 10 95.10 neut
Home field advantage = 1.45 goals. Chaminade and Duxbury are non-local games.
Table 2: Error Analysis
1 Lynbrook Error = (15- 6) + 1.45 - (99.75 - 93.52) = 4.22 2 Chaminade Error = (14-12) + 0.00 - (99.75 - 96.35) = 3 Manhasset Error = (20- 8) + 1.45 - (99.75 - 90.06) = 3.76 4 MacArthur Error = (20- 5) - 1.45 - (99.75 - 86.79) = 0.59 5 Floral Park Error = (15- 0) + 1.45 - (99.75 - 87.53) = 4.23 6 Syosset Error = (21- 3) - 1.45 - (99.75 - 87.38) = 4.18 7 Duxbury Error = ( 9- 3) + 1.45 - (99.75 - 97.40) = 8 Division-Levittown Error = (20- 2) + 1.45 - (99.75 - 82.66) = 2.35 9 Carey Error = (24- 2) - 1.45 - (99.75 - 81.37) = 2.17 10 Great Neck No Error = (18- 3) + 1.45 - (99.75 - 80.48) = -2.83 11 Wantagh Error = (13-10) - 1.45 - (99.75 - 95.10) = -3.10 12 Port Washington Error = (20- 6) + 1.45 - (99.75 - 87.94) = 3.64 13 Lawrence Error = (15- 7) + 1.45 - (99.75 - 88.12) = -2.18 14 Southside Error = (17- 2) - 1.45 - (99.75 - 85.26) = -0.94 15 Long Beach Error = (11- 3) + 1.45 - (99.75 - 87.02) = -3.28 16 Southside Error = (18- 4) - 1.45 - (99.75 - 85.26) = -1.94 17 Floral Park Error = (17- 9) + 0.00 - (99.75 - 87.53) = -4.22 18 Wantagh Error = ( 8-10) + 0.00 - (99.75 - 95.10) = -6.65 home field = 0.0 means the game was played on a neutral site
Table 3: Combined Errors
Opponent Score Opp PR Home Err
1 Lynbrook 15 6 93.52 1.45 4.22
2 Chaminade 14 12 96.35 0.00 0.00
3 Manhasset 20 8 90.06 1.45 3.76
4 MacArthur 20 5 86.79 -1.45 0.59
5 Floral Park 15 0 87.53 1.45 4.23
6 Syosset 21 3 87.38 -1.45 4.18
7 Duxbury 9 3 97.40 1.45 0.00
8 Division-Levittown 20 2 82.66 1.45 2.35
9 Carey 24 2 81.37 -1.45 2.17
10 Great Neck No 18 3 80.48 1.45 -2.83
11 Wantagh 13 10 95.10 -1.45 -3.10
12 Port Washington 20 6 87.94 1.45 3.64
13 Lawrence 15 7 88.12 1.45 -2.18
14 Southside 17 2 85.26 -1.45 -0.94
15 Long Beach 11 3 87.02 1.45 -3.28
16 Southside 18 4 85.26 -1.45 -1.94
17 Floral Park 17 9 87.53 0.00 -4.22
18 Wantagh 8 10 95.10 0.00 -6.65
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0.00
Garden City ................. 99.75
Thus we have computed gthe power rating for Garden City such that the sum of all errors is 0.0.