Comparative values, correlation and classification of basketball players based on the efficiency index and expert evaluation by coaches

Measuring the efficiency of athletes during competition has been a subject of interest both for experts and scientists in sports for more than a hundred years. Basketball has recognized in the 1940s how important it is to analyze efficiency indicators because these procedures allow coaches to increase their knowledge. There are two basic methods – objective and subjective – for evaluating the efficiency, or real quality of basketball players. The aim of this research is to establish the level of correlation between these two methods and to identify clusters, i.e. player hierarchy based on the results of both methods of efficiency evaluation. The sample of variables consisted of 12 basketball players who participated in the 2010 FIBA World Championships in Turkey. The subjective evaluation, also called expert evaluation, was performed by coaches of seven national teams that participated in the Championship. The objective evaluation was performed using the EEF efficiency index. The data was processed using z-scoring, the Pearson coefficient, and hierarchical cluster analysis. The Pearson coefficients of linear correlation between the efficiency index and the expert evaluation is r = 0.859 with a statistical significance of p ≤ 0.01. The cluster analysis distinguished two groups of players, which were named quality and super quality. The variance analysis showed that the probability of the clusters being equal is less than p ≤ 0.00. The research has shown that the evaluation by coaches is relevant and is fully consistent with the efficiency index formula. Also, the distinction of two groups of players by clustering is not uncommon in the basketball practice and is linked with efficiency at the given time.