Tag Archive for volleyball service strategy

Service errors vs. service points

volleyball serve

I previous wrote the post Looking at Serving Risk and Reward. In it I broke down the risk/reward prospects of serving aggressively by way of a formula. Mark Lebedew and his research partner Ben Raymond posted an analysis of 2018 Volleyball Nations League serving. It basically takes that idea and applies it to real world statistics. There are a number of different graphs which are worth looking at showing the trade-off between service errors and point scoring % (referred to as breakpoint %).

For the most part, when you look at the graphs you see a line with a hump. Point scoring percentages are lower when service errors are lowest. They then rise as errors increase, but only up to a certain point. After that the extra errors negatively impact point scoring. In other words, there’s a kind of sweat spot where the risk and reward of serving aggressiveness balance to give the best point scoring percentage.

I can speak to this idea from personal experience. One season when I coached at Brown there was a point when I noticed our serving effectiveness had dropped off. In my analysis I realized we were only on 1-2 errors per set. We were at our best when it was 3-4, so I encouraged our servers to get more aggressive.

Here’s a basic example from the report.

In the report you’ll see different curve samples based on match data. In fact, no two teams had the same result. For example, the USA graph shows they were best with a notably higher error rate than we see for any of the other teams – at least for that particular match.

It’s worth noting that in one case there was no hump in the plot. That was from when France played Korea. The line for France in that match was entirely downward sloping from left to right. That means added service aggression was actually counterproductive. They were better off just keeping the ball in play.

This speaks to what I wrote in the Play conservatively to win, redux post, as well as to a story Iradge Ahrabi-Fard told in his Volleyball Coaching Wizards interview. There are certain situations or opponents where missing serves is to be avoided.

It’s definitely worth evaluating your own team(s) from this perspective.

Looking at scoring streaks, odds, and service strategy

I like to engage with other coaching bloggers when I can. It’s a form of networking, which is never a bad idea. It also helps to foster communication and the exchange of ideas in our coaching community.

To that end, I want to address a post I came across. The author is Jim Dietz, though his name isn’t actually anywhere on the site (at least as I write this). Jim coaches at the junior college and club levels in the US. Like me, he’s also a book author.

In Jim’s post he takes on the subject of scoring points in streaks in volleyball, having looked at some numbers about bunch scoring in baseball. The conclusion that the post eventually leads to is that once you’ve scored two points in a row there’s an argument to be made for focusing on getting the next serve in to sustain the streak.

Baseball first

A quick thought on the baseball comparison Jim makes before shifting to volleyball. My immediate question about teams scoring in bunches being more successful is whether it’s a function of getting more players on base. I don’t know the statistics, but that’s the first thing I’d want to look at. If that’s the case, it means they are giving themselves more opportunities to score in general. As such, it’s not a case of winning because of scoring in bunches, but rather scoring in bunches because that’s what happens when you get a lot of runners on base, which produces more runs generally.

Scoring streaks required

Now, let me address the volleyball side of scoring streaks.

First, you simply cannot win a set in volleyball without scoring points in a row. This is the no-brainer aspect of Jim’s analysis. At the end of the day, points scored when you serve are what decides the game. In order to score a service point – aside from when you have the first serve of the set – you must first side out. That’s two points in a row – a mini streak.

If teams could only score at most one point from serve, then the team that had the greater number of mini streaks would win the set. Of course, it doesn’t work like that. Teams can run off multiple points when they have serve.

But with regards to Jim’s analysis, there’s a major causality question – as there could be in the case of the baseball stats. Does a team win because they score in bunches? Or does the better team just tend to score in bunches?

Looking at the odds

Jim’s analysis of randomly generated scores are actually very predictable. Even when you have something like a coin toss you will get streaks. Given enough tosses, it’s guaranteed. And when a streak does happen, the odds aren’t in favor of a comeback, so to speak.

Let me drill down on that. Say it’s 15-15 and one side has a 3-point streak to get it to 18-15. If the odds of siding out are 50% for both teams, then you’d expect them to score basically the same number of service points over the rest of the set. That would mean something like a 25-22 score line. Is there a chance that the losing team gets a streak, or even more than one? Yes, but it’s just as likely the leading time does so. That means the odds of the leading team winning are quite high.

The above provides a good basis for going along with what Jim says about trying to go for streaks. The problem, though, is that this is all based on the idea that point scoring is entirely a random process with fixed odds. If that’s the case, then nothing we do really changes things. But do we really believe the odds are fixed? Maybe when looking at large numbers of observations. At the set level, though, there are a lot of factors that can alter the odds.

Impact on serving strategy

And that brings up the big point I want to make.

Jim talks about not being as aggressive on your 2nd serve as on your 1st to increase the odds of getting that 3-point streak (counting the original side out). There’s a major flaw in Jim’s thinking, though. In theory, if you dial down the aggressiveness on your serve you lower your chances of scoring. Jim speaks as if doing so increases the odds of scoring. If that were the case, wouldn’t you just use that less aggressive serve all the time?

That said, I do think it can be the case that you want to focus on getting your serve in in certain circumstances. These, though, are situations where you believe the odds have shifted more in your favor – going back to the earlier point of odds changing. For example, the other team is looking error prone and you don’t want to let them off the hook by making your own. Again, though, if you believe that’s the case already then your 1st service strategy should already reflect this view.

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