Tag Archive for volleyball statistics

Considering a set rating system

In my Volleyball player efficiency ratings post I referred to a short paper proposing a way to evaluate setting. That paper is A Reconceptualisation of Traditional Volleyball Statistics to Provide a Coaching Tool for Setting by Alexis Lebedew. The paper’s basic idea is to combine a pass/dig rating (like the kind mentioned here) with a 0-3 rating for the outcome of a spike to get a set rating (0 for error, 3 for kill). The pass rating is effectively inverted. Good results off poor passes are rated higher than ones off good passes. This accounts for set decision and/or execution.

Conceptually, I like the idea proposed by the paper. There are a couple of issues with this particular ranking process, though.

No real new information

The set rating system was evaluated to see if it related to the probability of winning a set. It does, but that’s no real surprise since it is heavily influenced by outcomes. Specifically, with the highest ratings coming on kills. We already know that getting a lot of kills generally results in more winning. We also know that both hitting efficiency and pass quality relate to scoring points and winning sets. As a result, we don’t really have any additional information from this rating in that context.

Problematic comparisons

Hitter skill is a major factor in attacking outcomes. Good hitters can make up for poor sets. Poor hitters, though, struggle even with great sets. Further, the quality of the block and defense the hitters face is a meaningful factor in attack outcomes. As such, it is problematic to compare setting across teams. A great setter on a poor team simply won’t rate as well as a setter on a good team.

So what to do

If the underlying idea of rating sets is to be able to compare setters directly then I fully support factoring in pass quality. It is the primary control variable determining what can be done with any given setting opportunity. Including it allows us to look at setting on an even playing field.

In order to really assess the quality of sets, though, we need to also be controlling for the outcomes in a similar way we do for passing. If a passer puts up a perfect pass, we don’t punish them because the setter mishandled the ball, nor do we bump up their pass rating because the setter was able to put up a good set off a poor pass. I think we end up circling back to the idea of rating sets similarly to how we rate passes. The problem, though, is we really should be factoring in play calling and decision making in the process, which is no easy thing.

All that said, though, I do think the type of set rating proposed in the paper could be useful in comparing setters on the same team or in a situation where teams and players are quite similar in level of play. In that case, hitting quality and the block/defense of the opposition would presumably be the same for each, allowing for a level assessment.

Volleyball player efficiency ratings

A while back I came upon a 3-part series of blog posts. It conceptualizes a unified way of looking at volleyball statistics across all categories. It’s dubbed the Volleyball Player Efficiency Rating by its creator. The three installations are here, here, and here respectively. The second refers to a paper on setter-specific ratings I address separately in another post. A number of folks came up with different variations on the player efficiency theme in the recent years.They are interesting conceptual exercises. At least the stat geek side of me thinks so!

When I coached at Brown I even developed one myself. I dubbed it the Point Contribution Ratio. Basically, I took the basic match stats for kills, blocks, digs, and assists. I then added in the 0-3 ranking we did for serve reception and the 0-5 score we used for serving into the mix. Each stat was weighted based on how directly it contributed to points scored or conceded. The calculation looked something like this:

PCR = Kills + Blocks + Aces + 0.5 x Assists + 0.5 x 3-passes + 0.25 x 2-passes + 0.5 x 4-serves + 0.25 x 3-serves – Hitting Errors – Service Errors – Ball-Handling Errors – Block Errors

That’s not exactly it, but I think you probably get the idea. Comparison was made on a positional basis because of the way different positions scored. Setters, for example, had the highest PCR because of their assists.

I never did actually test the PCR out statistically, though. That means I can’t give you an idea of how useful it might have been given the right weightings. Therein lies the problem with many of these volleyball statistical measures. We don’t know if they are meaningful when it comes to winning and losing points and matches. Jim Coleman actually did the statistical work on passing. He showed that how a team passed on the 0-3 scale related to their probability of scoring points (see his chapter in The Volleyball Coaching Bible). Those who propose new statting methods must do the same. Those who use statistical techniques to evaluate teams and players need to know that they actually have a measurable relationship to what we’re using them for. They can’t just sound good. Otherwise, we’re just spinning our wheels to no real purpose.

Where do your team’s points come from?

In his book, Thinking Volleyball, author Mike Hebert offers up a typical scoring chart for his college teams based on winning a 25-point set. It looked like this:

Kills 12
Opponent Errors 8
Terminal Blocks 2.5
Service Aces 2.5

I only share the specific numbers above as an example. It should not be taken as indicative of where your team should be in its point scoring distribution. These numbers are from upper level women’s NCAA Division I play. A typical distribution for teams at other levels, and on the men’s side, could vary considerably. For example, at lower levels of play I’d expect to see the influence of kills and blocks reduced, with errors and aces increased.

The point isn’t the specific numbers above, but the idea behind them. As coaches, we should have a good handle on how we score points and how we give them up. That allows us to set training priorities and develop match strategies. Additionally, if we know the point scoring balance of our leading competitors, we can get some sense of where our team needs to be, if it isn’t there already.

For example, going into this past season I knew the women’s university team I coached needed to get stronger in the attack. The prior year we could defend with just about anyone and keep our errors down, but we couldn’t get as many kills as we needed to compete at the top level. Recognizing that, from the very start of the season this year I focused on a more aggressive attack. We were never a dominant offense, but we improved enough within the scope of our overall play to reach the national semifinals.

Caution in thinking about these numbers is required, though. It’s easy to look at the table above and think something like “Well blocks and aces don’t account for very many points, so we should focus our time elsewhere.” The problem with that kind of mindset, though, is that while blocking and serving may not directly translate into a lot of points, they both contribute to them indirectly by putting the opposition under pressure, forcing mistakes or easier transition opportunities. So don’t just think all you need to do is work on hitting!

Player-centric volleyball stat collecting

In an issue of the AVCA’s Coaching Volleyball magazine there was an article on the collection and use of stats. It’s a pretty comprehensive discussion. It focuses, however, on the more basic stats, not the higher end stuff that some coaches use these days. The author takes the perspective of a coach in a small program where there isn’t much in the way of help for collecting stats during training, etc.

That article made me think about making the stat collection process more player-centric.

I wrote before about player-centric drills, which in contrast to coach-centric ones put players in charge of initiating the process. For example, a passing drill where players serve is player-centric. One where the coach serves is coach-centric.

So how can we take coaches out of the stat-taking process? Basically, players must keep track of serves, passes, hits, or whatever. This is in place of a coach (or manager) doing so. The article mentions doing something like having passers write down how they did in a serve receive drill. There obviously are other ways you can do this.

I’ve mentioned my own personal struggles keeping stats while my team is in action. I really don’t like having to take my eyes off the play to tick a box on a clipboard or tap a tablet. Working by myself, or with limited coaching help, while I was at Exeter and Svedala, I was forced to find ways to do what I wanted or needed to do in terms of training. I had to give some thought to how I can do the same thing with stat collection.

Ideas are certainly welcome!

Thinking about my use of stats

Back when I coached in England I came across a thread on a forum asking the members which statistics they find most useful in their coaching. It got me thinking about my own use of statistics at that time.

I’ve talked in prior posts about what was available to me when I coached collegiately in the States. I’ve also discussed the sorts of things I used at times when coaching in England. College volleyball coaches in the States use stats all the time. During matches they get print-outs after each set of the standard stuff. Many also keep serving and passing tallies, and sometimes other things as well. I definitely can get way into the numbers at times. I like to look at things from all different angles and perspectives (see this Boston Globe article for a discussion of advanced stats in the NBA).

In England there were no official stats coming my way during matches. Anything that I did have access to necessarily meant either myself or my assistant had to record them. I found that I had a very hard time doing that because it splits my focus too much. I did some in-training stats, mainly in the area of serve receive. The bottom line ended up being I didn’t use stats very much.

Actually, I didn’t find myself missing them all that much. Granted, stats are very good for giving you an objective view of things. Assuming you have enough reps to have a meaningful set of numbers, of course. That bit tends to be a problem. There is a tendency among at least some coaches (and players) to jump to conclusions based on a limited sample. This is a really bad idea. Stats are good for seeing broad patterns, not for making quick analysis.

I actually think not having all the stats I used to have helped me be a better coach in those days. Because I didn’t have the crutch of the numbers, I was forced to pay much closer attention to patterns of play. Was my OH playing the way she did when she was attacking successfully? Or was her body language telling me this is not going to be her best hitting match? Was my libero going with purpose to the ball the way she did when she passed serve best? Or was she being more passive as she did when she passed poorly?

Basically, what was happening then is that I was not just looking at outcomes, but also seeing causality. If I was just looking at the stats, all I’d see is outcomes. There are a lot of things which influence those that are out of a player’s control. It’s a process vs. result type of focus, which is something I’ve always had to a degree, but really firmed up during my time in England.

Having said all that, I did think it would be better for volleyball in England if there were consistent stats available from competitions like BUCS. They would have provided the basis for telling better volleyball stories to expand the exposure of the sport.

Key resources for volleyball coaches

There’s a list of tools and resources posted up on the USA Volleyball blog. Some of the stuff is the sorts of tools we can use on the court and/or should have to be prepared for emergency situations. Some of them I’m sure you’ll have in mind – and potentially already have in your coaching bag – but some might not have occurred to you before. There’s also a list of computer programs and apps. Here’s the latter:

BAM Video Delay –  show “mirror like” on the face of the tablet whatever the lens is set to show, but by rubbing your finger on the face of the tablet, you can delay longer or shorter up to 2 minutes.  Player does whatever on the court, then before the 15 seconds, or whatever time set amount, goes over to the tablet to see their skill performance. Coach does not need to be present. http://www.orangeqube.com/bustamove/

Dartfish Express – or Ubersense, or Coaches Eye – fast replay video options for in practice feedback, which includes the ability to draw lines/angles, and more to assist.

Scoreboard  – Simply turns your tablet into a “flip score” device  easy to read from across the court. https://itunes.apple.com/us/app/scoreboard-free-version/id496758984?mt=8

VBStatsHD – Does all the stats/video synching you want and more – not cheap – but not expensive at $30. For those who want a powerful app. – http://peranasports.com/?portfolio=vbstatshd-demonstration

ACE Stats/Tap Recorder – Low cost fast stat software.  http://www.ace4vb.com/smart-device-store.html

I’ve used a couple of these apps myself, and have written about TapRecorder specifically. I’d love to hear your experience with any of the above, or whatever other applications you’ve used.

The good and the bad of volleyball statistics

Coach Rey has an interesting post discussing the use of stats in modern volleyball. It includes an idea for his own sort of team scoring metric. I found his comments about how complex and advanced stats are these days to be quite interesting. I’d started having that feeling as well at times. I can imagine how overwhelming the mass of numbers are for some. In particular, Rey brings up how confusing things can be for players. I think that is probably something which varies from player to player. Some don’t care about stats while others get quite into them.Personally, from a player perspective, I like to use stats to help track development and performance over time. I also like to provide points of comparison where appropriate.

I can imagine coaches getting too caught up in the numbers. This is a little bit of the PhD in me talking. The fact of the matter is that as coaches we tend to get only small sample sizes. You need a fairly large number of observations to draw proper conclusions. This is fine in a situation where you can track lots of reps (like serve receive over several training sessions). It’s more problematic when you have to make quick judgements in the middle of a match. For example, when a hitter has 10 swings, 1 kill or 1 hitting error either way has a major impact on their hitting %.

And let’s face it. There’s a lot of stuff that goes on in a volleyball match which doesn’t show up in the stats. Having numbers at hand makes it seem like we can make nice clean assessments. The bottom line, though, is that we’re still dealing with people. People aren’t machines. Inevitably there are things they do (or don’t do) which aren’t so easily converted into neat objective measures. Some coaches seem to get so obsessed with the numbers that they forget this fact.

Don’t get me wrong! Stats are quite handy so long as one doesn’t get carried away.

While coaching in England I was jealous of the stats my coaching peers back in the States got. There is very little in the way of statistics there, and most of what does exist comes from coaches collecting their own. I did a bit of stat-tracking in training to give players progress reports and to do some comparisons. At one point I had an assistant who tracked some things during matches when he was available. That’s about as far as it went, however.

I struggle personally as a head coach to keep stats during matches because I find it distracts me from observing the big picture of what’s going on with my team (different when I was an assistant). I wouldn’t have minded having consistent box score type stats provided to me, though. 🙂

Coaching Log – Nov 25, 2013

This is an entry in my volleyball coaching log.

With matches for everyone coming up, playing 6 v 6 in segregated teams was the main theme of training. The B side focus was on teamwork, calling the ball, staying switched on, and not looking for someone else to play the ball. I told the B side focus was on continuing to be aggressive in attack, but underlying that was also an evaluation of the setter position. This harkens back to my observations from the Student Cup performance.

One of my primary OHs thus far is also a capable setter (sets for her German club team). I haven’t used her there thus far because I saw her value as an attacker as being in the area of greater need. Even had to use her at MB on a couple of occasions when we were thin on bodies. In the last match of the Cup I had her do some setting for the first time and it was an eye-opener just from the warm-ups. With other hitters coming along, I no longer feel so concerned about losing out on her as an OH.

At the same time, our starting setter up to now is only here for this term. As a result, I need to evaluate our setting options moving forward in any case. One of the teams on the schedule for the upcoming matches is currently top of the table, having beat us a couple weeks ago. We need to be at our best for the rematch, so I took a hard look at the setting in training to start evaluating who would give us our best chance at victory.

Following what was basically a pre-match warm-up, we went straight into 6 v 6. It started with a game featuring one side serving 3 times in a row (not counting missed serves). I put the starting setter with the B team (their setter was missing) and the other one with the A team. I used that to gauge a rough baseline point differential I could use to spot the B side in the straight-up games to follow. I came up with 8.

We then played two regular games which started with the B side serving, up 8-0. In the first the starting setter was with the A side. I then flipped setters for the second game. The A team lost the first set 25-20, and the second 25-23.

Stats were kept for all three games to evaluate offensive effectiveness as a way to compare the setters. More of this needs to be done in the next training, but the early results show quite a stark difference. The kill % for the team when the starting setter ran things on the A side was was 21% vs 36% for the former OH, while the hitting efficiency numbers were .063 vs .190. Need to see if that gap holds up.

Volleyball Coaching App Review: TapRecorder

A while back, I looked into apps I could potentially use to help keep track of statistics in practice. I didn’t want to resort to going the old clipboard method. I wanted something that went beyond just match type stats. That’s in terms of being able to cover the whole squad at once rather than just 6 players. I also want to do more than just the standard kills, blocks, digs, etc.

Most of the apps out there are oriented toward match stating. I did find one which seemed to fit the bill, though. That was TapRecorder from Volleyball Ace.

TapRecorder What really attracted me to TapRecorder was its flexibility. It is based on a spreadsheet model, making it highly customizable. Basically, you can keep track of just about anything you like. In my case, I could do something like putting all my players on a single screen and track their passes in a serve receive drill.

The app comes with a set of sample recordings (downloadable from the website). You can use either on their own or as the basis for developing your own templates. Creating new recording sheets is pretty easy. I can be a bit tedious when you need to add in a long list of players, however. There’s a companion application which will allow you to do it on your computer for upload to the tablet. I haven’t used it yet, though.

As with any stating app, there’s going to be a little bit of a learning curve, though designing your own recording sheets helps to at least make things more intuitive for you. And obviously if you’ve only got TapRecorder on one device only one coach at a time can use it, which is no different than working with a clipboard. You’d need multiple versions of the app to have more than one coach stating, but there’s a companion desktop application (Excel-based) which will allow you to aggregate data from multiple recordings. I haven’t used that yet myself, but when I do I’ll add my observations here.