As individual’s cognitions and behaviours are affected by where they live, the reliability of responses to tests or scales may vary with location. In this paper, we develop a local version of Cronbach’s alpha, geographically weighted Cronbach's alpha, to investigate how the reliability of the measure varies spatially. Two demonstrations of exploratory applications of the three-wave geocoded measure of “social capital index” in the Baltimore metropolitan area, USA, was also performed in this paper.