Iowa's RPI on CBS.com daily rankings dropped from 5 to 10 after MSU lost to Nebraska. RPI is a double edged sword kind of poll. Iowa did nothing different in the 1 day, but drops 5 spots because other teams lost. Some teams get better (like Iowa), and some teams lose their mojo/focus/toughness after a couple losses (MSU). Can't take the polls too seriously until the end of the season.
It just amazes me that one team that you have played loses a close game (albeit at home), and you drop big time. So I guess that Kansas losing by 20 at KSU should have dropped all teams that played them by 5 spots? . RPI is way too confusing.
The system is always changing because it uses opponent's records and opponent's opponent's records. It's actually a pretty straightforward formula:
RPI = (win% x .25) + (opp% x .5) + (oppopp% x .25)
There are a couple tweaks beyond that. Results against the team being calculated are ignored. Also, the team's own win % is adjusted to factor home/road/neutral site. There's a full FAQ here:
http://www.collegerpi.com/rpifaq.html
Since strength of schedule is 75% of the formula, teams can easily move up and down without playing. It is also blind to history, so it sees MSU only based on their record and SOS this year. It does not look forward, so Izzo's history of March surges means nothing. It also ignores margin of victory, injuries, travel distractions, weather, narrative, rivalry, coaching situation, game flow, off nights, on nights, star signs, and everything else that might influence an individual game. The RPI is really meant to measure the relative quality of team records at the conclusion of a given season. Looking at it with a major percentage of the conference season yet to go is dicey.
It may end up being that MSU's just not that great this year. Or that we inflicted some kind of psychological damage to them. Whatever. What's important is we've beaten them twice and are making a run to the top of the Big Ten standings. Given the history of these teams, it was important to us to get over that hump, whatever state they may be in. In short, just win, baby.