2.6 Statistical Analysis of Improvement Factors
Pulse check length and percent compression fraction were the primary outcomes of this study. Statistical analysis of pulse check length and percent compression fraction throughout the study period was performed by way of Spearman’s rank correlation coefficient, a standard approach to detect trends over a specific time period. The coefficient, rho, is a measure of rank correlation between time and an outcome measure with the null hypothesis that there is no (monotonic) increase or decrease in the outcome measure over the study period. A rho of +1 or -1 indicates a perfect correlation in the positive or negative direction, respectively, while a rho of zero indicates no change in the outcome measure over the study period. Statistical significance was defined by p<0.05 in the analysis unless noted otherwise.  All statistical analyses were performed using STATA (Stata Corp. Release 16. College Station, TX; Stata Corp LLC.).