Guides · Measuring · 9 November 2026 · Thomas Schüller
Reading success rates correctly
Why five successful attempts out of ten say little, how the uncertainty range helps and how many attempts you need.
Five out of ten attempts succeeded, so 50 percent. At the next session it is seven out of ten. Has the team improved? Perhaps, perhaps not. With small numbers a rate varies strongly without anything having changed. Lames and McGarry show that many performance indicators in game sports vary markedly from match to match.
The uncertainty range
The Wilson interval gives the range in which the true rate lies with about 95 percent confidence. For five out of ten it runs from about 24 to 76 percent, for 50 out of 100 from about 40 to 60 percent. If the ranges of two measurements overlap strongly, a difference is not shown.
Clear rules before counting
Hughes and Franks stress that every observation needs a clear definition. Agree beforehand what counts as an attempt and what as a success, and count practice and matches separately.
How to use it
Collect attempts over several sessions before you judge. The tactics board always shows the rate with its range and marks values below ten attempts.
Key point: A rate without an uncertainty range invites wrong conclusions; only many attempts make differences visible.
References
- Wilson, E. B. (1927): Probable inference, the law of succession, and statistical inference. Journal of the American Statistical Association 22(158), 209-212.
- Lames, M.; McGarry, T. (2007): On the search for reliable performance indicators in game sports. International Journal of Performance Analysis in Sport 7(1), 62-79.
- Hughes, M.; Franks, I. M. (Hrsg.) (2004): Notational Analysis of Sport: Systems for Better Coaching and Performance in Sport, 2. Auflage. Routledge, London. ISBN 9780415290050.