Why I like KO%

Plus the DV Manual is now free for SmarterVolley subscribers

Here’s an image to ponder, from a club coach:

Pts/Serve is ultimately what we care about the most. At the end of the day, we need to score points, so the servers that are scoring the most points are (barring something like an exceptionally-poor or good defensive rotation for the server) our best servers. All the statistics we take are basically attempting to say, “here’s the server that’s going to score the most points, assuming they have an equal team around them.”

We can see pretty clearly that Serve-In % has a pretty low correlation with Pts/Serve. We can see that Ace % has a better correlation, but it’s still not perfect. And we can see KO % has the best correlation.

This isn’t surprising. KO % is a more comprehensive stat (it measures Aces + Out-of-System passes and it contains a bit of Serve-In as well), so we expect it to have a higher correlation to success. What’s great about KO % is that it’s also easy to understand. It’s human scale. The best servers on this team (as tends to be the case in HS/club volleyball) are at about 67% KO, which is about, “2 out of 3.” That human scale makes it easy for players to understand and process.

What Is KO%?

KO% or Knockout % is the frequency which a server knocks the other team out of system. If you’re on a 3pt scale, that means either forces a 2 or a 1-pass. If we’re talking DV, it means forcing R!, R-, R/, or scoring a direct ace.

Something I like about KO% is that it automatically incorporates “serving tough” with “serving in.” Ace:error ratio isn’t a bad measure either, it’s just incomplete. It also gets thrown off by very low-error servers, who are usually not your worst point-scorers but often not your best. So KO% tends to do a bit better at predicting which servers will score the most points than Ace:Error ratio.

Another nice thing about KO% is that, since it’s a human-scale number, it incorporates well into drills. At the high school level, you might challenge servers to get 2-out-of-3 or 4-out-of-6 Knockouts to win a mini-round. At the NCAA level, you’re looking more like 4/5-out-of-10.

The flip side of KO% is Good Pass % or In-System %, but remember that Knockout also incorporates missed serves. So a server with 10% error and 50% KO is not allowing 50% Good Pass. On 10 serves she serves 5 KOs, 1 Error, and 4 Opponent Good Pass. So the Good Pass is 4/9 = 44%. Just a minor note in case you’re calculating this from back stats.

And finally, if you want to learn how to program these stats and more, I’ve now moved my Unofficial Guide To DV4 Mastery off the old ScoutVB server and I’m hosting it on SmarterVolley, free for any premium subscribers. Check it out! (Behind the paywall if you aren’t a premium subscriber yet.)