Department of Chemsitry, T. S. Paul Manipur Women's College, Monsangei, Imphal-795 008, India Department of Chemistry, School of Sctence, Manipur University, Canchipur, Imphal-795 003. India Department of Physics, Krishnath College, Berhampore-742 101, Murshidabad, India Manuscript received 20 April 1999, accepted March 2000 An attempt has been made to find out precisely the error involved in the determination of activation energy by Coats and Redfern method. We also consider the case of temperature dependent frequency factor. The findings have been tcsted by evaluating activation energies from theoretical as well as experimental thermogravimetry curves of solid state reactions.