Coverage and Precision of Net Promoter Score Confidence Intervals Across Sampling Distributions

Thomas M. Menino Convention & Exhibition Center 

The Net Promoter Score (NPS) is widely used to measure customer loyalty, yet theoretical challenges limit its practical application. Using simulations and an unbiased variance estimator, we evaluate coverage and width of Wald, bootstrap t, and adjusted Wald confidence intervals under four population shapes: extreme, triangular, uniform, and left-skewed. With increasing sample size, coverage approached the nominal 95% level for all methods except under the extreme population shape. The adjusted Wald method with triangular or uniform weights was most robust when the population shape was unknown, with comparable interval widths at moderate to large sample sizes. Interval width depended on population shape, and the Wald and bootstrap t methods performed poorly at small sample sizes. These results clarify the sampling behavior of NPS, provide a theoretical basis for unbiased variance estimation, support reliable confidence interval construction, and inform applied use and future methodology.

Confidence interval

Sampling distribution

Net Promoter Score (NPS)

Adjusted Wald 

Section on Statistics in Marketing