I recently discovered that the American Volleyball Coaches Association (AVCA) makes its bimonthly magazine, Coaching Volleyball, free online. Naturally, I reviewed the last several issues in search of any statistically oriented articles and I hit paydirt.
UC San Diego assistant men's coach Tristan Burton, who earned a Ph.D. in mechanical engineering from Stanford with a 2003 dissertation entitled "Fully Resolved Simulations of Particle-Turbulence Interaction," contributed an article to the latest (August/September 2009) issue of Coaching Volleyball.
The title of Burton's AVCA article says it all: "A Comprehensive Statistics System for Volleyball Match Analysis." Whether using the game (set) or match as the unit of analysis, the system decomposes the final total point difference between the teams into seven categories.
As a concrete example, Burton uses the 2008 Olympic men's semifinal between the U.S. and Russia. With the U.S. winning 25-22, 25-21, 25-27, 22-25, 15-13, the Americans garnered 112 total points to the Russians' 108. The Americans' +4 overall differential could then be broken down into the following components (where PD = Point Difference):
Service (SPD)
1st Ball Attack (1PD)
Transition Attack (TPD)
Opponent Terminal Serve (OTSPD)
Opponent Giveaway Transition Attack (OGTPD)
Opponent Block and Cover Transition Attack (OBACTPD)
Miscellaneous (MPD)
As Burton notes, "Given that the service line is not an advantageous location from which to attack, [one's own service performance] is usually a negative number, i.e. on average a team loses points when they serve" (p. 17). In the example Olympic match, the U.S. had an SPD of -51, whereas for Russia it was -58.
The Americans' seven component scores, listed in the same order in which the terms appear above, were -51, 40, 9, 15, -6, -3, and 0, which sums to +4 (corresponding to the U.S. team's winning four more total points in the match than the Russians, as detailed above). Russia's sum would naturally come out to -4 (-58, 35, 17, 11, -6, -3, 0). I have not explained how each of these component scores is obtained; these procedures are fairly complicated, so interested readers will need to look at Burton's original article to see how everything works.
As Burton advises, "In addition to looking at these statistics for the entire team, it is also possible to look at them for individual players or individual rotations in order to identify more specific areas for improvement" (p. 18).
Burton's system is not for the faint-of-heart. It requires extensive manual record-keeping during a match and the use of computer software to calculate the various parameters. The article has so many variables and abbreviations that it will almost certainly leave any reader's head spinning (it did mine, and as a professor who teaches statistics, I'm usually quite comfortable with numbers and formulas).
Another potential use of Burton's article would be to select a few relatively straightforward tabulations to use for one's team, instead of immersing oneself in the full system. One statistic in the article that caught my eye is the following: "Russia was able to respond to slightly more (73.9% vs. 73.4%) serves with a 1st ball attack" (p. 17). I would have thought such elite teams would have more of a tendency to mount an attack directly off of serve receipt, but by the same token, I guess, elite teams would also be delivering a lot of tough serves!
ADDENDUM/CLARIFICATION: Dr. Burton and I have exchanged e-mails, in an attempt to clarify the statistic in the paragraph immediately above regarding teams' mounting a 1st ball attack only around 73-74% of the time. These figures include opponents' serving errors as non-1st ball attacks. Dr. Burton was kind enough to run some new numbers for readers of the blog. Limiting the situation to when a receiving team faced an in-play serve, how often did the receiving team successfully set up a spike attempt as a first response, as opposed to being aced or sending a feeble (i.e., freeball) response back to the serving team? The answer is generally around 90%, both from some Olympic men's and Pac-10 women's matches Dr. Burton analyzed.
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1 comment:
The P-2 statistics (FIVB ) presents following data of this match
USA Russia
service 8 3
block 7 11
attack 66 66
Opp errors 31 28
Total 112 108
It appear s hence that in spite of better blocking the Russians lost by more reception errors
( aces) and opponent errors the difference explains well the four points. A statistic to explain win or loss should be simple and based on a minimum of parameters as shown in this example. Regression analyses of team ranking do show mostly a single significant parameter as attack efficiency and a second factor usually is opponent errors and only in rare cases service or block may come up as a significant parameter. More detailed analyses as shown may shed light on other aspects but are not required to explain in a simple way match results. The example of USA Russia is a poor example with attack points as usually the difference in attack point s only may explain the result.
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