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Predicting NBA Games With Home-Away Averages

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Updated February 21, 2013

Predicting NBA Games With Home-Away Averages

Here, we'll take a look at a slightly different way of handicapping NBA games. It is a bit similar to some of the other methods we have previously looked at, but does have several key differences, primarily the scoring averages that are used. Since we have reached the NBA's All-Star break, there have now been enough games played where you can use separate stats for home and away games.

This method uses league average/league median, which is something that's been discussed a number of times and will give predictions for both sides and totals.

The Method

The stats required are simply the average league scoring for both home and away teams and the average home or away scoring for the two teams involved in the game you wish to predict.

Using an NBA game with Milwaukee at Brooklyn for an example, the first thing you will need is the average points scored and allowed by home teams in the league. Teams that are at home average 98.5 points per game and allow 95.2, so naturally road teams score 95.2 and allow 98.5.

Next, you will compare each team against the league average in both offense and defense to come up with a percentage of how that team does compared to the league average.

Milwaukee is averaging 96.6 points on the road and allowing 97.7. You will divide Milwaukee's points for into the average points scored by road teams, giving you 96.6/95.2=1.011, which means Milwaukee's offense scores 1.1% more points than the average road team.

Next, divide Milwaukee's points allowed of 97.7 by the average points allowed by road teams, which is 98.5 and you will get 97.7/98.5=.992, meaning Milwaukee allows .8% fewer points than the average road team.

The home team, Brooklyn, averages 97.4 points at home and allows 94.8, so you will divide 97.4 by 98.5 and get .989, meaning Brooklyn scores 1.1% fewer points than the average home team, and you will divide 94.8 by 95.2 and get .996, which means Brooklyn allows .4% fewer points at home than the average team.

To calculate a team's predicted score, you multiply its offensive percentage by its opponents' defensive percentage by the league average. For Milwaukee, you will have 1.011*.996*95.2=95.862. Your predicted total for Milwaukee in the game is 95.862 points.

For Brooklyn, you will have .989*.992*98.5=96.637, which is the predicted total for Brooklyn. Your line on the game would have Brooklyn favored by .775 or 1 point and a total of 192.499 or 192.5.

The actual line on the game, which was played Tuesday, Feb. 19, was Brooklyn -4.5 with a total of 194.5 and the Nets escaped with a 97-94 victory, which was pretty darn close to our prediction on the game. (If they were all so easy.)

Unlike the other methods that require you to either add several points to the home team or subtract from the road team and add to the home team, here there is no adjustment that needs to be made, as you are using home and away averages, so the home court factor is already built into your numbers.

Our sample size is still close the lower limit, meaning there are enough games home and away games that have been played to be able to use those stats separately, but just barely. So I would probably look for differences of at least five points between your prediction and the line for both point spreads and totals.

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