Ken Pomeroy explains:
Since these are adjusted win probabilities, games involving non D-I teams are not included. While you might be looking for raw win probability, adjusted is the only way to go. Nobody was watching the opening moments of the Kansas/Alcorn State game with any notion that the game would be competitive, even when Alcorn State somehow scored the first four points. From a strategy standpoint, this is how the participants are (or should be) looking at the game.
If you’re a regular visitor, then you’ll be able to pick up on what’s going on with a little effort. The only new concept in the chart is leverage, which is a take-off of Tom Tango’s baseball version. It measures how much is at stake on a particular possession. The cut-offs for the five categories are fairly arbitrary at this point. You can think of it as a proxy for the watchability of a game at that point.
The colors range from blue, where win probability is largely unaffected by the potential outcome of a possession, to yellow, where the outcome of a possession can have significant impact on the win probability (more precisely, at least a 10% swing between a 2-point possession and zero points). Leverage is not based on what happened during the possession, but is the range of win probability based on what could have happened.
So what the heck is win probability?
The Win Probability for a specific situation in baseball (including the inning, number of outs, men on base, and score) is obtained by first finding all the teams that have encountered this situation. Then the winning percentage of these teams in these situations is found.
The Hardball Times offers a more extensive explanation here, and although it's also explained in the context of baseball, the concept is the same. It might also be a good idea to look at some baseball win probability graphs that are labeled so that the dots in Ken's graphs make more sense.
Getting to some graphs from NC State's season:
-- As much as I've tried to forget about The Great Parsons Disaster Of Aught Ten, I couldn't help but gawk at the wreck. State's win probability was in the neighborhood of 93% prior to Parsons's heave. I wonder if that's the biggest single-play swing in win probability that occurred in college hoops last year. It's hard not to marvel at it.
-- That was an unpleasant start, so let's move on to more enjoyable outcomes. Marquette's win probability was around 93% at halftime. Geronimo! With five minutes and some change to go, it was NC State's win probability that was around 93%. The graph of Florida State's destruction at the hands of Scott Wood is also quite stylish.
-- The Macrowave's late tie-breaker against Auburn increased State's odds by about 30%.
-- Here's Javi Time in full effect, and Nic Wise putting the kibosh on our fun shortly after his seventh or twelfth foul. Up 8 with 53 seconds to go, Arizona's win probability was around 90% and ultimately dipped all the way to about 69% as State came all the way back. It would have dipped much further had the foul been called on Javi's game-tying basket.