Confidence Limits on a Percent Defective Characterized by Two Specification Limits

Abstract

A quality problem is to assess the performance of a production process with respect to specifications. A solution is obtained by estimating the percent defective and placing confidence limits on the percent defective for each product characteristic. Tables are presented in this paper for determining a point estimate of the percent defective and 90, 95, and 99 percent confidence limits on the percent defective of a characteristic with both upper and lower or single specification limits. On the assumption of normality, only the specification limits, sample size, sample mean and standard deviation are needed to give a solution to the problem.

• Confidence Interval
• Percent Defective
• Specification Limits

Additional information

Notes on contributors

R. L. Kirkpatrick

Mr. Kirkpatrick is a Project Statistician in the Statistics Section of the Kansas City Division. He is a Senior Member of ASQC.