Monitoring, control and improvement of quality are important for companies. Process capability indices (PCIs) are tools widely used by the industries to determine the quality of their products and the performance of their manufacturing processes. Classic versions of these indices were constructed for processes whose quality characteristics have a normal distribution. But, many of these characteristics do not follow this distribution. In such a case, the classic PCIs must be modified to take into account the non-normality, because the effect of this non-normality can lead to misinterpretation of the process capability and ill-advised business decisions. A non-normal model is the Rayleigh distribution which is very useful. This paper proposes a Clements’s method to estimate the PCIs for Rayleigh processes. Finally, an example to evaluate its performance is presented.

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