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The theoretical study for the effect of Corticosterone release scores over a 24-hours light/dark period was determined. Formulae of fuzzy two parameter Weibull distribution, Log-Logistic and Exponential distribution, fuzzy reliability function and its α-cut sets are presented. Using fuzzy reliability model based on two parameter Weibull distribution, Log-Logistic distribution and Exponential distributions, we showed that the α-cut for the fuzzy reliability for the effect of release of Corticosterone by using Weibull distribution and Exponential distribution is comparatively better than other pair.