4 ms·

> The small spikes at 5 yard increments is interesting and I don't really have a good explanation other than to think that whoever recorded the yardage data lik

by sndean 8y ago

> The small spikes at 5 yard increments is interesting and I don't really have a good explanation other than to think that whoever recorded the yardage data liked rounding to the nearest 5 if it was close. Anyone else have any other ideas? I'll go with the idea that the refs are biased with their ball placement and tend to put the ball on lines [0]. Also, players/teams practice, speak, think in 5 yard increments, so that's got to bias things a bit. "We've got to get to the 35 yard line for Morten to have a chance." [0] https://gutterstats.wordpress.com/2015/11/03/are-nfl-officials-biased-with-their-ball-placement/ https://gutterstats.wordpress.com/2015/11/03/are-nfl-officia...

J253 8y ago
Thanks for the link! That's a great resource and write up about the statistical heaping effect. I'll include that in a post update.
dyim 8y ago
ha! that's funny. "We've got to get to the 35 yard line, so Morten can kick a 53-yarder, so we can have a chance."
slg 8y ago
There are multiple other factors involved that aren't discussed fully in that article. To start the ref bias is not necessarily unintentional. Measuring first downs and exact placement of the line of scrimmage becomes more difficult and takes more time when the ball is not initially spotted on an 5 yard increment or individual hash mark. The league offices might directly instruct refs to spot the ball on an exact yard line if there is any doubt of the spot in order to speed up the game. An obvious example of this intentional bias is when the ball is punted out of bounds. It is nearly impossible for a ref to get an exact spot in that situation and yet it is almost always spotted exactly on a hash mark. Also lots of drives will start on a set yard line and penalties are often handed out in 5 yard increments. So while there are no rules that will start a drive on the 15, there are rules that will start a drive on the 20 or 25 and a standard 5 or 10 yard penalty would place the ball exactly at the 15 yard line. Lastly, the spot is a continuous data point that is being recorded by humans as a discrete data point. That means the herding could be exaggerated in the recorded data and not necessarily as pronounced during the actual game. A ball might be spotted by the ref at 14.4 yards but the person responsible for data entry might eye the spot and record it as being at the 15 yard line.
forapurpose 8y ago
It also could be bias in the person recording the data, who may unconsciously prefer rounding placements between the 4 and 6 yard lines to 5.
endorphone 8y ago
While I have no explanation for the clustering, a yard is a long, long measure in football, with a dozen 4K cameras and a lot of very vested interests. Occasionally spots seem generous or not, but that's to the measure of a couple of inches (e.g. he went down 4" short of the first down). As a long time fan it just doesn't seem reasonable to me that the ref opts for the 40 yard line instead of the 39 because there's a line. That's a 3 foot difference. To further support this, the bordering two yard counts do not depress the amount of the excess on the 5 yard marker. Not to mention that where the refs place the ball -- near the center of the field, usually on the left or right side depending upon where the play ended -- has a line on every yard marker. But again I have no explanation. We know that touchbacks start on the 20 or 25 yard line, and penalties are increments of 5 yards (e.g. face mask would be 15 yards, holding 10 yards, false start 5 yards, encroachment 5 yards, etc...and these can pile, kickoff out of the last five yards starts at the 40 yard line, etc), and to some degree this explains the 5 yard excess.
swasheck 8y ago
I've often wondered if there was a way to detect bias in officiating. Naturally there's going to be subjective element to the types of penalties called, but I also have wondered if there was a way to detect bias in the situations in which penalties are called and how they affect the probability of victory. Additionally, with the whole Tim Donaghy [0] NBA thing, I have always been curious if there was a way to detect referee influence on the outcomes of games based on the line. There certainly times when Vegas loses (a few weeks ago was particularly bad for them), but it would be interesting to see if there was a way to detect probabilities of officials, coaches, or even players deciding the outcome of matches beyond the course of the endeavor. But really, it'd be fun to have statistical backing to confirm or refute the whole "College Football has a pro-East Coast bias" or "this referee always gives fouls to the European soccer sides", or "the Patriots _always_ get those calls because ... Tom Brady." [0] https://en.wikipedia.org/wiki/2007_NBA_betting_scandal https://en.wikipedia.org/wiki/2007_NBA_betting_scandal

by sndean 8y ago

J253 8y ago

Thanks for the link! That's a great resource and write up about the statistical heaping effect. I'll include that in a post update.

dyim 8y ago

ha! that's funny. "We've got to get to the 35 yard line, so Morten can kick a 53-yarder, so we can have a chance."

slg 8y ago

There are multiple other factors involved that aren't discussed fully in that article. To start the ref bias is not necessarily unintentional. Measuring first downs and exact placement of the line of scrimmage becomes more difficult and takes more time when the ball is not initially spotted on an 5 yard increment or individual hash mark. The league offices might directly instruct refs to spot the ball on an exact yard line if there is any doubt of the spot in order to speed up the game. An obvious example of this intentional bias is when the ball is punted out of bounds. It is nearly impossible for a ref to get an exact spot in that situation and yet it is almost always spotted exactly on a hash mark. Also lots of drives will start on a set yard line and penalties are often handed out in 5 yard increments. So while there are no rules that will start a drive on the 15, there are rules that will start a drive on the 20 or 25 and a standard 5 or 10 yard penalty would place the ball exactly at the 15 yard line. Lastly, the spot is a continuous data point that is being recorded by humans as a discrete data point. That means the herding could be exaggerated in the recorded data and not necessarily as pronounced during the actual game. A ball might be spotted by the ref at 14.4 yards but the person responsible for data entry might eye the spot and record it as being at the 15 yard line.

forapurpose 8y ago

It also could be bias in the person recording the data, who may unconsciously prefer rounding placements between the 4 and 6 yard lines to 5.

endorphone 8y ago

While I have no explanation for the clustering, a yard is a long, long measure in football, with a dozen 4K cameras and a lot of very vested interests. Occasionally spots seem generous or not, but that's to the measure of a couple of inches (e.g. he went down 4" short of the first down). As a long time fan it just doesn't seem reasonable to me that the ref opts for the 40 yard line instead of the 39 because there's a line. That's a 3 foot difference. To further support this, the bordering two yard counts do not depress the amount of the excess on the 5 yard marker. Not to mention that where the refs place the ball -- near the center of the field, usually on the left or right side depending upon where the play ended -- has a line on every yard marker. But again I have no explanation. We know that touchbacks start on the 20 or 25 yard line, and penalties are increments of 5 yards (e.g. face mask would be 15 yards, holding 10 yards, false start 5 yards, encroachment 5 yards, etc...and these can pile, kickoff out of the last five yards starts at the 40 yard line, etc), and to some degree this explains the 5 yard excess.

swasheck 8y ago

I've often wondered if there was a way to detect bias in officiating. Naturally there's going to be subjective element to the types of penalties called, but I also have wondered if there was a way to detect bias in the situations in which penalties are called and how they affect the probability of victory. Additionally, with the whole Tim Donaghy [0] NBA thing, I have always been curious if there was a way to detect referee influence on the outcomes of games based on the line. There certainly times when Vegas loses (a few weeks ago was particularly bad for them), but it would be interesting to see if there was a way to detect probabilities of officials, coaches, or even players deciding the outcome of matches beyond the course of the endeavor. But really, it'd be fun to have statistical backing to confirm or refute the whole "College Football has a pro-East Coast bias" or "this referee always gives fouls to the European soccer sides", or "the Patriots _always_ get those calls because ... Tom Brady." [0] https://en.wikipedia.org/wiki/2007_NBA_betting_scandal https://en.wikipedia.org/wiki/2007_NBA_betting_scandal