Continuous-flow stirred tank reactors (CSTR) are widely employed to elucidate the kinetics and dynamics of chemical reactions. Complete information regarding the spatial heterogeneity of micromixedness over the entire tank is essential for interpreting data and identifying the mixing effects. Therefore, in this work, we quantitatively estimate the segregation indices in a CSTR on the basis of a unique parallel competing reaction scheme proposed by Villermaux and co-workers. Experimental results indicate that the segregation index is a function of stirring rate as well as of the spatial location, from which, the mixing times can he estimated. Unexpectedly, although enhancing the micromixedness over the entire tank, a higher stirring rate cannot ensure a more uniform medium.