Interval Estimation for the 'Net Promoter Score'
  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. 
Brendan Rocks
stat.ME