Lies, damned lies, and statistics: a case study on why some stats are not to be trusted

So I was perusing through my Yahoo league and reading some news, notes and matchup recommendations when I stumbled upon this stat & recommendation for Jeremy Langford:

http://i.imgur.com/H2ls46z.png?1

The key stat being:

(Langford) should find more room to run against an Eagles defense that allowed 5.7 YPC last week.

Now, if I hadn't been an Eagles fan, I probably wouldn't have watched the Eagles-Browns game on Sunday. And if I hadn't watched the game I probably wouldn't have been able to immediately recognize that this YPC stat is entirely misleading and mostly BS. Yes, if you just take the total rushing yards and divide by attempts you get 5.7, but that stat is not useful information because it disregards context that paints a completely different picture. I'll break it down to explain....

Here are the details of the Browns rushing stats in Week 1

Total = 21 carries for 120 yards (5.7 YPC)

Right off the bat, since we're trying to compile an outlook for a RB, you have to remove the QB carries/yards. Not only were those carries/yards coming from a different position, but QB rushing yards are usually gained on passing plays and do not reflect the effectiveness of a team's Run Defense. Removing the QB carries/yards brings the totals down to...

Total = 16 carries for 83 yards (5.2 YPC)

i.e., after isolating rushing yards by actual rushers, YPC drops by 10%.

Now, that's not much of a difference, and despite the low total yds, 5.2 YPC is still a high average which might suggest that the original recommendation is still valid. However, there is still more context to apply beyond simply isolating rushers, context that would not be easy to recognize without having watched the game; 'garbage time context'.

Check out what happened at the end of the game in the last 1:12 (when the outcome was beyond doubt and the defense relaxed)

The last 3 plays of the game were irrelevant plays in garbage time, amounting to 3 rushes for 40 yards. These are 'gifted stats' which do not reflect on the opposing defense, so to have proper stat-context you would have to remove these rushes as well, which brings the totals down to ....

#Total = 13 carries for 43 yards (3.3 YPC)

And just like that, after applying a little bit of common sense context, a stat that suggested a weak run defense becomes a stat suggesting a strong run defense.

TLDR; context can dramatically change a broadly used statistic and suggest the opposite conclusion. So before you go making decisions based on stats, remember to check the underlying context to make sure it's not deceiving you.