The Power of the Pruned Exact Linear Time(PELT) Test in Multiple Changepoint Detection

Abstract

Changepoint detection is the problem of estimating the point at which the statistical properties of a sequence of observations change. Over the years several multiple changepoint search algorithms have been proposed to overcome this challenge. They include binary segmentation algorithm, the Segment neighbourhood algorithm and the Pruned Exact Linear Time (PELT) algorithm. The PELT algorithm is exact and under mild conditions has a computational cost that is linear in the number of data points. PELT is more accurate than binary segmentation and faster as than other exact search methods. However, there is scanty literature on the sensitivity/power of PELT algorithm as the changepoints approach the extremes and as the size of change increases. In this paper, we implemented the PELT algorithm which uses a common approach of detecting changepoints through minimising a cost function over possible numbers and locations of changepoints. The study used simulated data to determine the power of the PELT test. The study investigated the power of the PELT algorithm in relation to the size of the change and the location of changepoints. It was observed that the power of the test, for a given size of change, is almost the same at all changepoints location. Also, the power of the test increases with the increase in size of change.