The impreciseness happens in the quality control same as other statistical problems. In quality control where specification limits are better expressed by fuzzy sets, the generalized process capability indices C-(p) over tilde, C-(pk) over tilde and C-(pm) over tilde can be helpful and necessary for measuring the capability. We propose a generalized form of Taguchi index C-(pm) over tilde to assess the ability of the fuzzy process to be clustered around the target value. An approximate 100(1-gamma)% confidence interval for the generalized process capability index C-(pm) over tilde by using fuzzy specification limits is also presented.