The Most Recent, Earliest, and Kth Significant Changes in an Ordered Series: Traveling Backwards in Time to Assess When Annual Crude Mortality Rate Most Recently Began Increasing in McLean County, North Dakota

Paul R. Yarnold

Optimal Data Analysis, LLC

Serial or longitudinal measurement is widely practiced by people in all facets of real-world phenomena: an athlete wishes to know how many training sessions are required before significant increase in performance is realized; a musician wishes to assess how many on-stage performances are required before a significant increase in media attention is attracted; and a medical patient wishes to understand how many units of medication are needed before significant improvement in health is achieved. This paper discusses how to use UniODA to statistically evaluate a longitudinal series, either by starting at the series beginning and traveling forwards in time, or starting at the series end and travelling backwards in time. This is illustrated with an example involving backwards travel in a time-ordered series, to determine when recently observed statistically significant increases in annual crude mortality rate occurred in McLean County, North Dakota.

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