Social media such as Facebook and Twitter have become repositories for extremely large volumes of data representing for the most part, personal opinions and statements of individual users of these instruments for interpersonal communication. They provide a forum for discourse and debate. The strings of words broadcast by individuals are predominantly casual expressions reflecting personal attitudes or sentiments. Due to the pervasive nature of social media and the opinions they proliferate, it is assumed likely that these casual expressions are being relied on by some readers of the discourse, for their decision making influence. This paper describes how Change Point Analysis (CPA) can be used to bring some precision to the plethora of casually expressed sentiment sourced from social media databases. It is contended that where the conjunction of opinions expressed are related to a factual occurrence in time and space, a change point can be established, which indicates the potential reliability on a given sentiment as being a reliable influence factor for opinion formulation or other decision. When related to tourist destination data, the case study for Japan described here is convincing in its analytical result exposition