ABSTRACT
A perennial question raised by analysts is how many matches, or how many performances, do I need to gather to ensure that the analyses of my team’s (or athletes’) performance really represent their average performance, i.e. is it truly their normative profile? In previous notation research there has been little statistical basis to quantify the number of matches analysed in providing a performance profile. The essential question is whether a consistent state of performance per match has been reached to classify the data as a profile. Large variations in the frequencies of the individual variables between matches can often occur, and this gives no credibility to the presentation of these data as a performance profile. In one soccer match a striker may have ten or 12 shots; the following week the same striker has none. McGarry and Franks (1994) suggested that players exhibit greater consistency in play when matched against the same opponent than against a different opponent. The authors concluded that invariant athletic behaviour is dependent to a certain degree on the level of analysis used. It is an implicit assumption in notational analysis that in presenting a performance profile of a team or an individual a ‘normative profile’ has been achieved. Inherently this implies that all the means of the variables that are to be analysed and compared have all stabilised. Most researchers assume that this will have happened if they analyse enough performances. But how many is enough? In the literature there are large differences in sample sizes. Just trawling through some of the analyses in a variety of sports shows the differences (Table 10.1).
