Determining Statistical Characteristics of a Vehicle Emissions Audit Procedure

Abstract

The Environmental Protection Agency currently audits automobiles for emissions compliance at assembly plants with multiple attribute multiple staged sampling plans. This paper summarizes the auditing procedure and develops methods for determining its statistical characteristics. Specifically, we consider how to evaluate a multiple attribute multiple staged sampling plan, give a procedure that efficiently estimates attribute-type probabilities from multivariate variables-type data, and quantify the effect of tightening the acceptable quality level of the sampling plan. A key technique for this analysis is the multivariate version of the Box-Cox power transformation. All procedures are illustrated with data from a typical vehicle configuration.

KEY WORDS:

• Multiple attribute
• Multivariate normality
• Box-Cox power transformation
• Outliers
• Risk analysis