I started being interested in sports statistics at about the age of seven. Or at least that is my earliest memory of being interested. My first interest was cricket statistics. I found those numbers to be endlessly fascinating and wanted to know how they were arrived at, so I taught myself many basic maths concepts working out why someone’s average was what it was. Since that time, I have continued to be interested in the numbers of sport, an interest which has dovetailed nicely into my profession.
Specifically in volleyball, I have spent a lot of time thinking about the what, how and why of recording the statistics for volleyball. I have come up with the following three philosophical principles for recording statistics**. In my opinion, the statistics that we record and the values we give them, i.e. the raw data file, should:
- be an accurate reflection of the game, both the raw data and the derived statistics.
- contain a logical internal consistency.
- follow common sense.
There is quite a lot of overlap in these areas, but we can still begin at the beginning. Firstly, in terms of raw data, I would expect that a volleyball literate person, knowing the different symbols and codes, should be able to read the codes and create a reasonably accurate replay of the match in his head. In derived statistics, that same volleyball literate person should be able to see a match report or box score and create a reasonably accurate overall impression of the match; who were the better players, what were the keys to victory/defeat, what was the quality of the match, etc. Secondly, there should be a logical internal consistency within and between the skills. A block point should be defined essentially the same way as a spike or serve point. For example, if a serve that is shanked by the receiver counts as a ace, then a spike that is shanked by the defender must also be a spike point. What is a spike or a block should be defined consistently each time. In my own personal coding, I define what is a spike and what is a free/down ball, by how I would view the action if I were a spectator and the ball hit the floor. If I would consider it an attack point, I have to code it as a spike. If I would consider it a defensive error, I have to code it as a free ball. Another example, an overpass that is killed with a two handed ‘blocking’ action, should be defined as a spike as logically a block must be preceeded by a spike.
The most important thing is how common sense applies to these first two points. And of course, common sense, as the saying goes, is anything but common. For example, I have seen people scout free balls given over the net as attack attempts. According to the strict letter of the volleyball rules, a ball directed over the net is an attack. However, to record those actions as attack attempts does not increase our understanding of what actually happened nor provide us with an accurate impression of the match. In fact I would argue it hinders that ability. Another is the situation in which a blocker touches the net. Technically, the block fault ends the rally before the spike has reached its conclusion. By this strict understanding of the rule, no net touches should be recorded as attack points; it should be an attack in play and a block error. I have never seen anyone record a match is this manner though and it would not help our understanding of the game if they did. What is common is that all block net touches are automatically recorded as attack points. While this does have a logical consistency, it actually hinders our overall ability to understand the game. Common sense has to lead us to the point where we ‘ignore’ net touches that don’t otherwise affect the outcome of the rally (i.e. the spike ended the rally anyway) and only record those that interrupted a rally that would have continued. And in that case the attack cannot be recorded as a point, but must be only in play.
I often return to the forest and trees analogy. What we want from statistics is a beautiful, representative rendering of forest, that we can enter and study individual trees, the grass in between them and the animals running around if need be. Without beginning with a working philosophy of what we want we can spend too much on the pointless details of the individual trees, while putting them in the wrong places and forgetting the grass and animals, therefore losing the feeling of the whole forest. If we spend too much time on the trees we aren’t very good coaches.
** The statistics we end up with, and the analysis we carry out on them, are another discussion altogether. One that I would like to think I will get around to someday.
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