Increasing the Reliability of FMEA Evaluation by Modifying Rating Scales and Applying Pairwise Comparison Method

Abstract

Failure Mode and Effect Analysis (FMEA) is a frequently applied risk assessment methodology in different fields of industry. It provides the opportunity for deep analysis of risky events, connecting to their potential causes and effects. Due to its robust method, risk can be identified and managed but, because of its complexity, the assessment can be time-consuming, and the answers can be inconsistent. In the authors’ experience, the scale used to quantify the priority number can influence these outcomes. To identify and measure the significance level of this connection, a survey was organized with experts of digital manufacturing, who were asked to rank the probability of risk occurrence in planning a production process based on digital manufacturing principles. Participants had to use three assessment methods: 1) traditional ‘linguistic’ scale; 2) ‘ratio scale; 3) pairwise comparison. In the case of the linguistic scale, probabilities were defined by their descriptions and an integer between number 1 and 7. These numbers did not equal the probability percentage. In contrast, the ranks of the ratio scale equalled the ranges of probability percentage. In the pairwise comparison, risks were compared by the frequencies of their occurrences. The assessment results were compared by time-need, difficulty, priority list, and consistency. Time and difficulty were ranked by the survey participants on a 4-level scale. The priority list was created by the summarized rank values. In the consistency assessment, we looked at how the amended scale affects the assessment uncertainty. In addition, pairwise comparisons were used to examine the consistency of each expert’s evaluation and filter out those that were not accurate enough.