  The Net Promoter Score (NPS) is a novel summary statistic used by thousands
of companies as a key performance indicator of customer loyalty. While adoption
of the statistic has grown rapidly over the last decade, there has been little
published on its statistical properties. Common interval estimation techniques
are adapted for use with the NPS, and performance assessed on the largest
available database of companies' Net Promoter Scores. Variations on the
Adjusted Wald, and an iterative Score test are found to have superior
performance.
