A statistical method for the serial comparison of vector cardiograms

In the absence of quantitative clinical standards to detect serial changes in cardiograms, statistical procedures are proposed as an alternative. These procedures are preceded by a dimension reducing orthonormal transformation of the original digitized cardiogram into a lower dimensional feature space. In feature space, mul-tivariate test criteria are given for the detection of changes in covariance matrices or mean vectors of the cardiograms. The flexibility is provided to compare the cardiograms of the same individual pairwise or simultaneously. Some pertinent remarks are also made about controlling the overall level of significance and its impact on the application of these techniques to cardiograms of USAF pilots.