The purpose of this research is to introduce a new method for a deep interpretation of a result in a psychological therapy assessment. This method is to link subjective and objective effect sizes based on the fuzzy set theory. This paper is to describe a method in which two effects are integrated.Traditionally, doing a statistical test leads to a P-value. This index is obtained from classical statistical tests when a null hypothesis is being tested. The P-value is the main statistic for deciding a null hypothesis. The P-value is being criticized from many years ago. For another method is the clinical significance (effect size), this is to overcome some limitations of the P-value. In this paper, we introduce a method for integrating clinical significance (Therapist’s effect size) to the impact which is perceived by receivers of that effect (client’s effect size). This method helps psychological researchers to access a deep and broad interpretation of the results. This result can be of more reasonability and fitness with reality. The steps which should be taken for obtaining Fuzzy Perceived Effect size (FPE) will be discussed using a numerical example
