The Giants, Dolphins, and Simpson’s Paradox

by Chase Stuart on November 10, 2018

This year, the Giants are averaging 6.35 net yards per pass and 4.18 yards per carry. That’s below-average on both counts, as New York ranks 20th in both categories.

This year, the Dolphins are averaging 6.53 net yards per pass and 4.30 yards per carry. Miami ranks 15th in NY/A and 17th in YPC.

And yet the Giants are averaging more yards per play this year than Miami! How is that possible — after all, plays are just rushes or passes (including sacks), and the Dolphins are averaging more yards per pass and yards per rush. But New York has gained 5.70 yards per play this year, while Miami is averaging only 5.58 yards per play.

The answer, of course, is Simpson’s Paradox. We can also see an example of Simpson’s Paradox with Chicago. This year, the Bears are averaging 6.65 net yards per pass and 4.45 yards per carry. That’s above-average in both categories, as Chicago ranks 12th in both metrics. And yet the Bears rank below the Giants in yards per play, at just 5.65.

This is because the Giants pass a lot, and passes are more effective at gaining yards (even net of sacks) than rushes. The Giants have passed on a league-high 70% of plays, while Miami has passed on 58% of plays and the Bears just 54% of plays.

This happens with a few teams every year. The Jaguars are averaging 6.02 net yards per pass, 4.25 yards per rush, and 5.41 yards per play. The Redskins are averaging 6.12 net yards per pass and 4.33 yards per rush, and yet… Washington is only averaging 5.34 yards per play, a lower average than Jacksonville. That’s because the Jags have passed on 66% of plays, while the Redskins have passed on only 56% of plays.

The table below shows where each team this season ranks in net yards per pass, yards per carry, and overall yards per play.

Search:

Y/P Rk	Tm	NY/A	YPC	Yd/Play	NY/A Rk	YPC Rk	Pass Perc
1	Kansas City Chiefs	8.64	4.72	7.05	2	8	59.5%
2	Los Angeles Chargers	8.35	5.16	6.96	3	2	56.4%
3	Los Angeles Rams	8.73	4.78	6.89	1	6	53.4%
4	Tampa Bay Buccaneers	7.99	3.77	6.52	4	29	65.1%
5	Atlanta Falcons	7.76	4.07	6.45	6	24	64.6%
6	Pittsburgh Steelers	7.36	4.34	6.27	7	14	63.7%
7	New Orleans Saints	7.97	3.92	6.18	5	27	56%
8	Green Bay Packers	6.69	4.8	6.07	10	5	67.2%
9	Denver Broncos	6.35	5.16	5.89	19	1	61.6%
10	Carolina Panthers	6.35	5.11	5.8	18	3	56%
11	New England Patriots	7.1	4.05	5.79	8	25	57.1%
12	Minnesota Vikings	6.57	4.19	5.77	14	19	66.3%
13	Cincinnati Bengals	6.45	4.39	5.73	16	13	64.9%
14	Oakland Raiders	6.66	4.11	5.71	11	21	62.7%
15	New York Giants	6.35	4.18	5.7	20	20	70%
16	San Francisco 49ers	6.36	4.77	5.65	17	7	55%
17	Chicago Bears	6.65	4.45	5.65	12	12	54.5%
18	Houston Texans	7.09	3.95	5.63	9	26	53.6%
19	Detroit Lions	6.25	4.48	5.6	21	11	63.1%
20	Miami Dolphins	6.53	4.3	5.58	15	17	57.6%
21	Indianapolis Colts	5.98	4.68	5.51	26	9	63.7%
22	Seattle Seahawks	6.59	4.32	5.44	13	16	49.2%
23	Philadelphia Eagles	6.23	4.1	5.42	22	22	61.6%
24	Jacksonville Jaguars	6.02	4.25	5.41	25	18	65.6%
25	Washington Redskins	6.12	4.33	5.34	23	15	56.3%
26	Dallas Cowboys	5.67	4.84	5.3	28	4	55.5%
27	Baltimore Ravens	6.04	3.61	5.16	24	31	63.8%
28	New York Jets	5.82	4.08	5.06	27	23	56.3%
29	Cleveland Browns	5.21	4.54	4.95	30	10	60.9%
30	Tennessee Titans	5.66	3.86	4.8	29	28	52.5%
31	Arizona Cardinals	4.89	3.35	4.32	31	32	62.7%
32	Buffalo Bills	4.19	3.7	3.98	32	30	57.8%

This is why it is not useful to rank teams by yards per play (or, by extension, yards). The 2018 Giants and 2018 Dolphins (or Bears, or 49ers) show why.

Tagged as: Simpson’s Paradox

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