With just a few hours to go until the NCAA selection committee announces its tournament picks, it's time to start thinking not just about who is going to make it to the Big Dance but about what matchups they might face. That makes this the perfect opportunity to introduce an exciting new idea fresh from the spreadsheets bubbling at Giant Killers Central: the concept of Giant and Killer families.

As longtime readers know well, our Giant Killers statistical model predicts big NCAA upsets in three steps. We start with basic team power rankings, based on margin of victory and strength of schedule. Then we use regression analysis to isolate the "special sauce" variables that lead some teams to over- or underperform in Giant vs. Killer matchups. Then we apply those factors to current teams to see how much, beyond their basic strength, they resemble past Giants and Killers. (Here's a more detailed explanation.)

So far, so good. But what about style matchups? Our model rates Stephen F. Austin as a better Killer than Harvard, but couldn't there be specific opponents that find the Crimson more dangerous than the Lumberjacks? Now we can start answering that question, thanks to a data-mining technique called cluster analysis, conducted for us by Liz Bouzarth, John Harris and Kevin Hutson of Furman University.

Cluster analysis figures out how to sift through a bunch of items so that things that are similar to each other end up grouped together. Imagine a pizza with toppings that seem randomly strewn about. Cluster analysis can tell us whether some areas are heavy on pepperoni or mushroom and how to slice the pie to find those regions. Now think about a set of basketball teams; cluster analysis can tell us which statistical similarities unite various groups of teams. You already know that, say, Iowa State plays a very different brand of hoops from San Diego State. Now we have the statistical tools to relate their stylistic contrasts to how they are likely to play against particular Killers.

It turns out we can group Giants and Killers into four families apiece. We will run through them briefly then turn to matchup implications.

The four families of Giants

Giants are heavily defined by their rebounding tendencies. One family is the Roy Williams Giants, which pile up good-to-massive offensive rebounding percentages, usually with very tall players, average defensive rebounding and few forced turnovers. North Carolina, naturally, is a Roy Williams Giant this season, as was Gonzaga last season and West Virginia in recent campaigns.