Trend analysis of jaw jerk action potential-amplitude data

The amplitude of the jaw jerk action potential (MSP) is a parameter with potential diagnostic value. It has apparently a large and irregular variation which has not yet been subjected to a thorough analysis. It is important to know if samples of MSP contain trends. The occurrence of trends indicates that the average value is influenced in a principally different way by changes in the number of observations per sample than if trends do not occur. If, for instance, there is a positive linear trend in the data, this means that the average value is larger if the number of observations is small. Samples of MSPs therefore were recorded, using surface EMG electrodes in the masseter and the anterior temporal muscles of young and elderly subjects, and subjected to trend analysis. Trends of the 1--4th grade occurred in 51% of the samples. Both positive and negative linear trends were found and had about the same frequency. The trend components were, however, randomly distributed. Comparisons between groups may therefore be made without the claim of trend-free samples. This significantly facilitates the use of the parameter MSP-amplitude, since it is difficult to obtain samples which have a normal and identical distribution.