
Are NFL officials biased with their ball placement? - twrkit
https://gutterstats.wordpress.com/2015/11/03/are-nfl-officials-biased-with-their-ball-placement/
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hn_user2
This is actually true. But the numbers don't tell the entire story. Officials
are trained to be biased towards a major yard line on change of possessions.
Starting at a major line n these instances is insignificant to the drive. The
upside being it is one less series where a measurement would ever be required.

It is a trade off of game flow (less measurements) vs a small inaccuracy where
it doesn't matter.

Take a notice next game. A punt always gets spotted on a major yardline where
possible. A punt inside the 10 of course would not be possible. Rounding from
the 2 to the 5 would have a huge impact. Or if it lands and comes to rest
directly between two major lines.

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dsp1234
One item that I did not see discussed is the effect of penalties, which are
generally made in 5, 10, and 15 yard increments. This combined with the
relatively standard 20 yard start position could have an enhancing effect, or
be an alternate explanation for the phenomenon.

ex: The offensive team starts from the standard 20 yard line. Then during the
first play, a pass is made, and "block in the back" is called against the
defensive team. The penalty would be 10 yards, and would put the offensive
team at the 30 yard line for the start of the play.

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jessriedel
This is discussed in the reddit comments. (It was my first thought to.) The
weak consensus was that this is rare enough away from the 20 to not be enough
to account for the data, which shows a similar bias toward 5-yard increments
the entire length of the field. Further, there was an anecdotal report that
NFL referee training specifically advises them to err toward a 5-yard
increment in certain situations.

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huac
This is cool!

Couple notes - 1\. If 'normal' plays have a tendency towards a 10/20/30 yard
line, what about plays where the ball placement is challenged? Don't know if
your dataset has this, but under your framework, we'd expect to see a more
even distribution of placements because of increased attention, though
probably still with spikes at the 1 yard line and goalline. 2\. Even though
it's probably intuitive, the unimodal distribution of ball placements was cool
to see.

