Power rankings are always debatable. I don't buy into the gut feel methods most places use to determine their rankings, so I developed a formula a few years back that attempts to take at least some of the subjectivity out of the discussion. My approach is simple, I measure offensive and defensive efficiency based on the Yards Per Carry (YPC) and Yards Per Attempt (YPA), as well as points scored and points allowed. The formula to calculate "Team Strength" is as follows:
(YPC (offense) + YPA (offense) + Avg Pts/Game Scored) - (YPC (defense) + YPA (defense)+ Avg Pts/Game Allowed)
The formula has proven to be a pretty accurate predictor of success. Even in the first week of the 2008 season, 5 of the top 10 ranked teams were playoff bound. As with any statistic, it becomes more meaningful as the sample size grows. Usually, these become most meaningful after Week 3. In 2007, 9 of the top 10 ranked teams were playoff teams, with the lowest ranked playoff team coming in at #15. In 2008, 8 the top 10 were playoff teams, with Arizona being the lowest ranked playoff team at #19. I'm not sure any formula could have predicted their run.
If you'd like to see how teams rankings changed from 2008 to 2009, you can read more here.
Seattle, Jacksonville and Oakland have changes over 4. That is unusual this far into the season when the sample size has grown to a reasonable level. There is obviously symmetry in the Oakland/Seattle changes due to the Raiders blowout victory. The Seahawks drop a whopping nine spots in one week, and now fall into the category of having stats that don't support their 4-3 record. San Diego continues to try and justify their lofty ranking, despite a nasty record. Shocking to see three AFC West teams in the top eight.
Scatter chart of the rankings. This view helps to give you a view of how teams are grouped together. You will generally see tiers of strength develop as the season wears on. The top teams came back to the pack this week, further proving there does not appear to be a powerhouse this season.