For determination of the association between thumb posture and muscular load, two analysis methods were used: group correlations comparing signal means, and cross-correlations, the temporal correlation of each individual’s synchronized goniometer and EMG signals.
2.6.1. Group correlations between goniometry and EMG parameters
The Pearson Product–Moment correlation coefficient (Altman, 1991) was calculated between the various goniometry and EMG summary measures with the statistical software JMP® (Version 7.0, SAS Institute, Cary, NC, USA). Correlations greater than 0.6 were tabulated and subjected to further analysis. This correlation threshold was regarded as being strong enough for practical purposes and gives for n = 15 a p-value less than 0.02