The system bias derives from the league’s ambiguous definitions for assists and blocks, which has led to varying interpretations by scorekeepers, who are all hired by home teams across the league.

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Three reasons why NBA scorekeeper bias may negatively impact your winnings in fantasy basketball

May 04, 2017
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By Justin Wong

If you aren’t having any luck making the right picks in online, daily fantasy basketball games you may want to start taking notes.

A study led by SFU professional sports analytics researchers Matthew van Bommel and Luke Bornn has unveiled systematic bias in NBA scorekeeping for individual player stats, which could affect who walks away with a cash prize in daily fantasy leagues.

The system bias derives from the league’s ambiguous definitions for assists and blocks, which has led to varying interpretations by scorekeepers, who are all hired by home teams across the league.

“The variability of how these categories are recorded could have a profound impact on the outcomes of daily fantasy basketball leagues as well as other fantasy basketball formats,” says van Bommel. “Many of these leagues involve cash prizes, so this impacts many players who participate.”

The Fantasy Sports Trade Association estimates there are approximately 58.1 million people in North America who are participating in fantasy sports. According to the Wall Street Journal, DraftKings and FanDuel, two of the largest daily fantasy sports operators in North America, have awarded a combined $800 million in prizes across all sports in 2014 alone.

In this study, published by Springer, the researchers used a model to measure the influence of on-court game action that plays a role in recording assists. This allowed them to remove the impact of these variables in order to isolate the opinions and biases of the scorekeepers.

To do this they used the computing power of big data, analyzing the billion rows of data produced by NBA cameras that track the movement of players and the ball over the course of the 2015-16 season. They compared this data against the data from NBA box scores from ESPN.

The results of the model indicate that scorekeepers may have biases with regards to both passer positions and the individual passers. The researchers used the model to estimate the influence of scorekeeper biases on the assist totals of all NBA players . Their findings were astonishing.

For example, the study suggests that the Utah Jazz scorekeeper is extremely stingy when it comes to awarding assists to players. Of the 10 players who saw the largest negative impact, six were members of Utah Jazz, with Jazz star Gordon Hayward topping the list.

“In terms of impact on daily fantasy games, scorekeeper bias resulted in an average of 9.7 fewer assists being awarded in a game in Utah compared to a game in Atlanta. In the highly competitive world of daily fantasy, just a few of those assists could be the difference between winning money and losing money.”

van Bommel recently sat down with SFU News to share three reasons why NBA scorekeeper bias may negatively impact your daily fantasy basketball team.

Point guards get all the credit

van Bommel: “Centers were nearly eight per cent less likely to be credited with an assist compared to point guards making the same pass.”

Big names do not always equal big assist numbers

van Bommel: “Some big-name players (including Lebron James and Chris Paul) tended to get an extra individual boost from scorekeepers. But others actually needed to work harder to get their assists, notably Isaiah Thomas and Kevin Love.”

No love at home

van Bommel: “While many scorekeepers had biases that favoured the home team, there were several biased against the team that hired them. Players on the Sacramento Kings, Phoenix Suns, and Golden State Warriors all had their assist totals deflated when playing at home.”

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