Arthur Dempster was a prominent American statistician known for his contributions to the field of statistics and data analysis. He is best recognized for developing the Dempster-Shafer theory, which provides a framework for reasoning with uncertainty and has applications in various fields, including artificial intelligence and decision-making. Dempster was also influential in the area of Bayesian statistics, where he contributed to the understanding of how to update probabilities as new information becomes available. His work has had a lasting impact on statistical theory and practice, making him a key figure in modern statistics.