NFL 2021 Week 15 Predictions – Zoltar Looks to Rebound

Zoltar is my NFL football prediction computer program. It uses reinforcement learning and a neural network. Here are Zoltar’s predictions for week #15 of the 2021 season. It usually takes Zoltar about four weeks to hit his stride and takes humans about eight weeks to get up to speed, so weeks six through nine are usually Zoltar’s sweet spot. After week nine, injuries start having a big effect.

Zoltar:      chiefs  by    0  dog =    chargers    Vegas:      chiefs  by    3
Zoltar:       bills  by    7  dog =    panthers    Vegas:       bills  by  9.5
Zoltar:      browns  by    6  dog =     raiders    Vegas:      browns  by    5
Zoltar:       colts  by    1  dog =    patriots    Vegas:    patriots  by  2.5
Zoltar:   cardinals  by    5  dog =       lions    Vegas:   cardinals  by 12.5
Zoltar:     jaguars  by    2  dog =      texans    Vegas:     jaguars  by  3.5
Zoltar:    dolphins  by    9  dog =        jets    Vegas:    dolphins  by    7
Zoltar:     cowboys  by    0  dog =      giants    Vegas:     cowboys  by   10
Zoltar:      eagles  by    1  dog =    redskins    Vegas:      eagles  by  2.5
Zoltar:      titans  by    0  dog =    steelers    Vegas:      titans  by  2.5
Zoltar:     packers  by    0  dog =      ravens    Vegas:     packers  by    2
Zoltar:     broncos  by    4  dog =     bengals    Vegas:     bengals  by    3
Zoltar: fortyniners  by    6  dog =     falcons    Vegas: fortyniners  by  7.5
Zoltar:        rams  by    6  dog =    seahawks    Vegas:        rams  by    7
Zoltar:  buccaneers  by    6  dog =      saints    Vegas:  buccaneers  by 11.5
Zoltar:     vikings  by    0  dog =       bears    Vegas:     vikings  by    4

Zoltar theoretically suggests betting when the Vegas line is “significantly” different from Zoltar’s prediction. In mid-season I usually use 3.0 points difference but for the first few weeks and last few weeks of the season I go a bit more conservative and use 4.0 points difference as the advice threshold criterion. In middle weeks I sometimes go ultra-aggressive and use a 1.0-point threshold.

Note: Because of Zoltar’s initialization (all teams regress to an average power rating) and other algorithms, Zoltar is much too strongly biased towards Vegas underdogs. I need to fix this.

For week #15:

1. Zoltar likes Vegas underdog Colts against the Patriots
2. Zoltar likes Vegas underdog Lions against the Cardinals
3. Zoltar likes Vegas underdog Giants against the Cowboys
4. Zoltar likes Vegas underdog Broncos against the Bengals
5. Zoltar likes Vegas underdog Saints against the Buccaneers
6. Zoltar likes Vegas underdog Bears against the Vikings

For example, a bet on the underdog Colts against the Patriots will pay off if the Colts win by any score, or if the favored Patriots win but by less than the point spread of 2.5 points (in other words, by 2 points or less).

Theoretically, if you must bet $110 to win $100 (typical in Vegas) then you’ll make money if you predict at 53% accuracy or better. But realistically, you need to predict at 60% accuracy or better.

In week #14, against the Vegas point spread, Zoltar went 0-3 (using the conservative 4.0 points as the advice threshold. Overall, for the season, Zoltar is 48-42 against the spread (~53%).

Just for fun, I track how well Zoltar does when just trying to predict just which team will win a game. This isn’t useful except for parlay betting. In week #14, just predicting the winning team, Zoltar went 10-4 which is pretty good.

In week #14, just predicting the winning team, Vegas — “the wisdom of the crowd” also went 10-4, the same as Zoltar.

Zoltar sometimes predicts a 0-point margin of victory, which means the two teams are evenly matched. There are five such games in week #15. In those situations, to pick a winner (only so I can track raw number of correct predictions) in the first few weeks of the season, Zoltar picks the home team to win. After that, Zoltar uses his algorithms to pick a winner.



Left: This is a photo of the back of a Frosted Flakes cereal box from 1967. It had an interesting football game where you’d spin a spinner (or roll two dice) and use the chart to determine the output. An early simulation. A generation of American computer scientists were inspired by clever games such as this. Right: Cereal boxes have activities that target girls as well as boys. This is a box of Unicorn Cereal that has an art activity for girls.


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