Bill Simmons and the NFC West

In his weekly football column, Bill Simmons of ESPN.com harshly criticizes the NFC West. His main point of evidence is the NFC's west record since 2002 (go-go arbitrary end points). He posts this table in his article:

DIVISION RECORDS SINCE 2002

Division	W	L	T	Pct.
AFC East	273	247	0	.525
AFC North	260	258	2	.502
AFC South	287	233	0	.552
AFC West	255	265	0	.490
NFC East	279	240	1	.538
NFC North	240	280	0	.462
NFC South	266	253	1	.513
NFC West	218	302	0	.419

He could have justifiably manipulated the data a bit further to prove his point. Each division plays 12 inter-division games each year. Against itself, each division goes 6-6 in those games. That weights the numbers in the above table towards .500 . If he had subtracted those 96+ games (12 games a year x 8 seasons = 96 games) included in each of the division stats, the table would bolster his argument slightly. To whit:

I made two assumptions. Simmons includes the first two weeks of the current NFL season. I assume that no division games had been played yet, which was not the case. I also assumed that the 4 ties that happened in the past 8 seasons were not division games (at least one of them wasn't and perhaps both). There you have it. the NFC West winning percentage drops to .401. Eyeballing it it looks significant. 6 of the 8 divisions are within .050 of .500 and the NFC west is .052 away from the next weakest team. To formally prove that the .401 is statistically significant, a t-test could be set up assuming .500 as the mean. The standard deviation would have to be sampled from historical data which would necessitate some assumptions.