Most discussion of the RPI involves the weaknesses of the system. I haven\u2019t seen anyone come to its defense, but the RPI is not that bad, really. Let me clarify – in the middle of December it’s bad. But the RPI is a tool in the tournament selction process, so it’s not meant to be used until March.<\/p>\n
First, I think we can agree that the best thing the RPI has going for it is its simple formula. For those who don’t know, it’s<\/p>\n
25% x your winning percentage (WP) + 50% x your opponents’ WP + 25% x your opponents’ opponents’ WP<\/p>\n
More simply its 25% x WP + 75% x strength of schedule (SOS)<\/p>\n
It\u2019s not something one can compute in their head. But any dork with a computer can calculate the RPI. While many fans know the formula, nobody really knows how it works. Which leads me to the first of the three main complaints about the RPI:<\/p>\n
Complaint #1: \u00be of the RPI is out of a team\u2019s control.<\/strong><\/p>\n While it seems like an obvious truth, that\u2019s not how it works at all. To illustrate this let\u2019s look at the range of values for both winning percentage and strength of schedule among all teams in recent end-of-season RPI\u2019s.<\/p>\n So the portion in the team\u2019s control has a range of values of roughly .8827, while the portion out of a teams control only has a range of .2140. Even when one accounts for the fact the winning percentage is just 25% of the formula, it still turns out to have a bigger impact than SOS:<\/p>\n SOS plays an important role, but unless your SOS is in the bottom third of college basketball, a poor schedule can be overcome with a great record. For instance last year Weber St. had a schedule ranked 178 out of 327, but with a 25-3 record they were able to have an RPI rank of 41. This is the beauty of the RPI, you can\u2019t really schedule your way into a good rating as most people think. The more difficult your schedule, the harder it is to maintain a good record and therefore a good RPI. The range of values in the SOS is also part of the reason the RPI is useless early in the year. SOS has a much greater range this time of year, so it does control the ratings. But as the year progresses, everybody\u2019s SOS gravitates towards .500 and winning percentage becomes more important.<\/p>\n Next week: Complaint #2 \u2013 When winning still hurts.<\/p>\n","protected":false},"excerpt":{"rendered":" Most discussion of the RPI involves the weaknesses of the system. I haven\u2019t seen anyone come to its defense, but the RPI is not that bad, really. Let me clarify – in the middle of December it’s bad. But the RPI is a tool in the tournament selction process, so it’s not meant to be […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/posts\/998"}],"collection":[{"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/comments?post=998"}],"version-history":[{"count":0,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/posts\/998\/revisions"}],"wp:attachment":[{"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/media?parent=998"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/categories?post=998"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/tags?post=998"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\nYear Max WP Min WP Diff Max SOS Min SOS Diff<\/b>\n2001 .9286 .0385 .8901 .6127 .4080 .2047\n2002 .9286 .0385 .8901 .6099 .4064 .2035\n2003 .9063 .0385 .8678 .6123 .3796 .2337\nAvg. .8827 .2140\n\n\n<\/pre>\n
\nWP: .25 x .8827 = .2207\nSOS: .75 x .2140 = .1605\n<\/pre>\n