The present study proposed a new statistical measure to find out the association between Drug-Adverse Drug Reaction (ADR) pair in the Pharmacovigilance system. The study proposed a subjective Bayesian measure corresponding to Proportional Reporting Ratio (PRR) parameter for quantitative signal detection. Classical and Bayesian inference procedure were used in analysis with four Drug-ADR pair as an example. We made prior information by expert opinion. The result of this analysis shows that Bayesian inference is more reliable as compared to classical inference. This study suggests that in case of spontaneous reporting in Pharmacovigilance system subjective Bayesian inference better to applying in case of small sample size.